EGU General Assembly 2022  

I will review the main magnetosphere-ionosphere (MI) coupling mechanisms thought to play a role at Jupiter and at Saturn. We are interested in the extent to which the magnetospheres are driven by internal processes (plasma sources, planetary rotation) versus external mechanisms (solar wind, interplanetary magnetic field). At both planets, momentum is mostly transferred via the rotating planetary magnetic field from the ionosphere to the magnetosphere. The solar wind can also play a role in driving dynamics, e.g. via the interaction of corotating interaction regions (CIRs). The NASA/ESA Cassini Huygens mission revealed that Saturn’s system also has a unique feature driven by the ionosphere known as “planetary period oscillations”. These phenomena interact with the effects of the solar wind to produce complex MI coupling signatures. The NASA Juno mission has provided the first in situ evidence of MI coupling in Jupiter's polar magnetosphere. I will compare the similarities and differences between observation and theory discovered thus far.

How to cite: Bunce, E.: Magnetosphere-Ionosphere Coupling and Aurora at Jupiter and Saturn, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11375, https://doi.org/10.5194/egusphere-egu22-11375, 2022.

A long-standing question within Saturn’s magnetosphere is the source of the ubiquitous oscillations, known as planetary period oscillations (PPOs). From radio and magnetometer data it is known there are two such oscillation systems, one in the northern hemisphere and the other in the southern. In this talk, we will review analyses of azimuthal magnetic field data from the Cassini mission right up to its end in 2017 which show the presence of field-aligned currents. Using these data, several field-aligned current systems are shown to be present in Saturn’s auroral regions and their relationship with the PPOs was revealed. The implications of these results on Saturn’s periodicities, aurora, and coupling between the ionosphere and magnetosphere will be discussed.  

How to cite: Hunt, G.: Saturn's field-aligned current systems as observed by the Cassini mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13335, https://doi.org/10.5194/egusphere-egu22-13335, 2022.

The recent developments in computer vision research in the field of Single Image Super Resolution (SISR)

can help improve the satellite imagery data quality and, thus, find application in planetary exploration.

The aim of this study is to enhance planetary surface imagery, in planetary bodies that there are

available data but in a low resolution. Here, we have applied the holistic attention network (HAN)

algorithm to a set of images of Saturn’s moon Titan from the Titan Radar Mapper instrument in its

Synthetic Aperture Radar (SAR) mode, which was on board the Cassini spacecraft. HAN can find

correlations among hierarchical layers, channels of each layer, and all positions of each channel, which

can be interpreted as an application and intersection of previously known models. The algorithm used

in our case-study was trained on 5000 grayscale images from HydroSHED Earth surface imagery dataset

resampled over different resolutions. Our experimental setup was to generate High Resolution (HR)

imagery from eight times lower resolution (x8 scale). We followed the standard workflow for this

purpose, which is to first train the network enhancing x2 scale to HR, then x4 scale to x2 scale, and

finally x8 scale to x4 scale, using subsequently the results of the previous training. The promising results

open a path for further applications of the trained model to improve the imagery data quality, and aid

in the detection and analysis of planetary surface features.

How to cite: Maxheimer, D., Markonis, I., Jan, M., Vojtech, C., Jan, P., and Anezina, S.: Enhancing planetary imagery with the holistic attention network algorithm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-486, https://doi.org/10.5194/egusphere-egu22-486, 2022.

Lineaments are prominent features on the surface of Jupiter's moon Europa. Analysing these linear features thoroughly leads to insights on their formation mechanisms and the interactions between the subsurface ocean and the surface. The orientation and position of lineaments is also important for determining the stress field on Europa. The Europa Clipper mission is planned to launch in 2024 and will fly by Europa more than 40 times. In the light of this, an autonomous lineament detection and segmentation tool would prove useful for processing the vast amount of expected images efficiently and would help to identify processes affecting the ice sheet. 

We have trained a convolutional neural network to detect, classify and segment lineaments in images of Europa returned by the Galileo mission. The Galileo images that make up the training set are segmented manually, following a dedicated guideline. For better performance, we make use of synthetically generated data to pre-train the network. The current status of the work will be described.

How to cite: Haslebacher, C. and Thomas, N.: Autonomous lineament detection in Galileo images of Europa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-692, https://doi.org/10.5194/egusphere-egu22-692, 2022.

The Waves of HIgh frequency and Sounder for Probing Electron density by Relaxation
(WHISPER) instrument, is part of the Wave Experiment Consortium (WEC) of the CLUSTER II
mission. The instrument consists of a receiver, a transmitter, and a wave spectrum
analyzer. It delivers active (when in sounding mode) and natural electric field spectra. The
characteristic signature of waves indicates the nature of the ambient plasma regime and, combined
with the spacecraft position, reveals the different magnetosphere boundaries and regions. The
thermal electron density can be deduced from the characteristics of natural waves in natural mode
and from the resonances triggered in sounding mode, giving access to a key parameter of scientific
interest and major driver for the calibration of particles instrument.
Until recently, the electron density derivation required a manual time/frequency domain
initialization of the search algorithms, based upon visual inspection of WHISPER active and natural
spectrograms and other datasets from different instruments onboard CLUSTER.
To automate this process, knowledge of the region (plasma regime) is highly desirable. A Multi-
Layer Perceptron model has been implemented for this purpose. For each detected region, a GRU,
recurrent network model combined with an ad-hoc algorithm is then used to determine the electron
density from WHISPER active spectra. These models have been trained using the electron density
previously derived from various semi-automatic algorithms and manually validated, resulting in an
accuracy up to 98% in some plasma regions. A production pipeline based on these models has been
implemented to routinely derive electron density, reducing human intervention up to 10 times. Work
is currently ongoing to create some models to process natural measurements where the data volume
is much higher and the validation process more complex. These models of electron density
automated determination will be useful for future other space missions.

How to cite: De Leon, E., Gilet, N., Vallières, X., Bucciantini, L., Henri, P., and Rauch, J.-L.: Automatic detection of the electron density from the WHISPER instrument onboard CLUSTER II, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1014, https://doi.org/10.5194/egusphere-egu22-1014, 2022.

Spectroscopy provides important information on the surface composition of Mars. Spectral data can support studies such as the evaluation of potential (manned) landing sites as well as supporting determination of past surface processes. The CRISM instrument on NASA’s Mars Reconnaissance Orbiter is a high spectral resolution visible infrared mapping spectrometer currently in orbit around Mars. It records 2D spatially resolved spectra over a wavelength range of 362 nm to 3920 nm. At present data collected covers less than 2% of the planet. Lifetime issues with the cryo-coolers prevents limits further data acquisition in the infrared band. In order to extend areal coverage for spectroscopic analysis in regions of major importance to the history of liquid water on Mars (e.g. Valles Marineris, Noachis Terra), we investigate whether data from other instruments can be fused to extrapolate spectral features in CRISMto these non-spectral imaged areas. The present work will use data from the CaSSIS instrument which is a high spatial resolution colour and stereo imager onboard the European Space Agency’s ExoMars Trace Gas Orbiter (TGO). CaSSIS returns images at 4.5 m/px from the nominal 400 km altitude orbit in four colours. Its filters were selected to provide mineral diagnostics in the visible wavelength range (400 – 1100 nm). It has so far imaged around 2% of the planet with an estimated overlap of ≲0.01% of CRISM data. This study introduces a two-step pixel based reconstruction approach using CaSSIS four band images. In the first step advanced unsupervised techniques are applied on CRISM hyperspectral datacubes to reduce dimensionality and establish clusters of spectral features. Given that these clusters contain reasonable information about the surface composition, in a second step, it is feasible to map CaSSIS four band images to the spectral clusters by training a machine learning classifier (for the cluster labels) using only CaSSIS datasets. In this way the system can extrapolate spectral features to areas unmapped by CRISM. To assess the performance of this proposed methodology we analyzed actual and artificially generated CaSSIS images and benchmarked results against traditional correlation based methods. Qualitative and quantitative analyses indicate that by this novel procedure spectral features of in non-spectral imaged areas can be predicted to an extent that can be evaluated quantitatively, especially in highly feature-rich landscapes.

How to cite: Fernandes, M., Thomas, N., Elser, B., Rossi, A. P., Pletl, A., and Cremonese, G.: Extrapolation of CRISM based spectral feature maps using CaSSIS four-band images with machine learning techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2765, https://doi.org/10.5194/egusphere-egu22-2765, 2022.

Solar flares and coronal mass ejections (CMEs) are the main drivers for severe space weather disturbances on Earth and other planets. While the geo-effects of CMEs give us a lead time of about 1 to 4 days, the effects of flares and flare-accelerated solar energetic particles (SEPs) are very immediate, 8 minutes for the enhanced radiation and as short as about 20 minutes for the highest energy SEPs arriving at Earth. Thus, predictions of solar flare occurrence at least several hours ahead are of high importance for the mitigation of severe space weather effects.

Observations and simulations of solar flares suggest that the structure and evolution of the active region’s magnetic field is a key component for energetic eruptions. The recent advances in deep learning provide tools to directly learn complex relations from multi-dimensional data. Here, we present a novel deep learning method for short-term solar flare prediction. The algorithm is based on the HMI photospheric line-of-sight magnetic field and its temporal evolution together with the coronal evolution as observed by multi-wavelengths EUV filtergrams from the AIA instrument onboard the Solar Dynamics Observatory. We train a neural network to independently identify features in the imaging data based on the dynamic evolution of the coronal structure and the photospheric magnetic field evolution, which may hint at flare occurrence in the near future.

We show that our method  can reliably predict flares six hours ahead, with 73% correct flaring predictions (89% when considering only M- and X-class flares), and 83% correct quiet active region predictions.

In order to overcome the “black box problem” of machine-learning algorithms, and thus to allow for physical interpretation of the network findings, we employ a spatio-temporal attention mechanism. This allows us to extract the emphasized regions, which reveal the neural network interpretation of the flare onset conditions. Our comparison shows that predicted precursors are associated with the position of flare occurrence, respond to dynamic changes, and align with characteristics within the active region.

How to cite: Jarolim, R., Veronig, A., Podladchikova, T., Thalmann, J., Narnhofer, D., Hofinger, M., and Pock, T.: Interpretable Solar Flare Prediction with Deep Learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2994, https://doi.org/10.5194/egusphere-egu22-2994, 2022.

The magnetopause (MP) and the bow shock (BS) are the two boundaries bounding the magnetosheath, the region between the magnetosphere and the solar wind. Their position and shape depend on the upstream solar wind and interplanetary magnetic field conditions.

Predicting their shape and position is the starting point of many subsequent studies of processes controlling the coupling between the Earth’s magnetosphere and its interplanetary environment. We now have at our disposal an important amount of data from a multitude of spacecraft missions allowing for good spatial coverage, as well as algorithms based on statistical learning to automatically detect the two boundaries. From the data of 9 satellites over 20 years, we identified around 19000 crossings of the BS and 36000 crossings of the MP. They were used, together with their associated upstream conditions, to train a regression model to predict the shape and position of the boundaries. 

Preliminary results indicate that the obtained models outperform analytical models without making simplifying assumptions on the geometry and the dependency over control parameters.

How to cite: Ghisalberti, A., Aunai, N., and Michotte de Welle, B.: Magnetopause and bow shock models with machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5721, https://doi.org/10.5194/egusphere-egu22-5721, 2022.

Mantle convection plays a fundamental role in the long-term thermal evolution of terrestrial planets like Earth, Mars, Mercury and Venus. The buoyancy-driven creeping flow of silicate rocks in the mantle is modeled as a highly viscous fluid over geological time scales and quantified using partial differential equations (PDEs) for conservation of mass, momentum and energy. Yet, key parameters and initial conditions to these PDEs are poorly constrained and often require a large sampling of the parameter space to find constraints from observational data. Since it is not computationally feasible to solve hundreds of thousands of forward models in 2D or 3D, some alternatives have been proposed. 

The traditional alternative to high-fidelity simulations has been to use 1D models based on scaling laws. While computationally efficient, these are limited in the amount of physics they can model (e.g., depth-dependent material properties) and predict only mean quantities such as the mean mantle temperature. Hence, there has been a growing interest in machine learning techniques to come up with more advanced surrogate models. For example, Agarwal et al. (2020) used feedforward neural networks (FNNs) to reliably predict the evolution of entire 1D laterally averaged temperature profile in time from five parameters: reference viscosity, enrichment factor for the crust in heat producing elements, initial mantle temperature, activation energy and activation volume of the diffusion creep. 

We extend that study to predict the full 2D temperature field, which contains more information in the form of convection structures such as hot plumes and cold downwellings. This is achieved by training deep learning algorithms on a data set of 10,525 2D simulations of the thermal evolution of the mantle of a Mars-like planet. First, we use convolutional autoencoders to compress the size of each temperature field by a factor of 142. Second,  we compare the use of two algorithms for predicting the compressed (latent) temperature fields: FNNs and long-short-term memory networks (LSTMs).  On the one hand, the FNN predictions are slightly more accurate with respect to unseen simulations (99.30%  vs. 99.22% for the LSTM). On the other hand, Proper orthogonal decomposition (POD) of the LSTM and FNN predictions shows that despite a lower mean relative accuracy, LSTMs capture the flow dynamics better than FNNs. The POD coefficients from FNN predictions sum up to 96.51% relative to the coefficients of the original simulations, while for LSTMs this metric increases to 97.66%. 

We conclude the talk by stating some strengths and weaknesses of this approach, as well as highlighting some ongoing research in the broader field of fluid dynamics that could help increase the accuracy and efficiency of such parameterized surrogate models.

How to cite: Agarwal, S., Tosi, N., Kessel, P., Breuer, D., and Montavon, G.: Deep learning for surrogate modeling of two-dimensional mantle convection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5739, https://doi.org/10.5194/egusphere-egu22-5739, 2022.

The Spectrometer Telescope for Imaging X-rays (STIX) is an instrument onboard Solar Orbiter. It measures X-rays emitted during solar flares in the energy range from 4 to 150 keV and takes X-ray images by using an indirect imaging technique, based on the Moiré effect. STIX instrument
consists of 32 pairs of tungsten grids and 32 pixelated CdTe detector units. Flare Images can be reconstructed on the ground using algorithms such as back-projection, forward-fit, and maximum-entropy after full pixel data are downloaded. Here we report a new image reconstruction and
classification model based on machine learning. Results will be discussed and compared with those from the traditional algorithms.

How to cite: Xiao, H., Krucker, S., Ryan, D., Battaglia, A., Lastufka, E., László, E., Dickson, E., and Wang, W.: STIX solar flare image reconstruction and classification using machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6371, https://doi.org/10.5194/egusphere-egu22-6371, 2022.

Since deployed on the Martian surface, the seismometer SEIS (Seismic Experiment for Interior Structure) and the APSS (Auxiliary Payload Sensors Suite) of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission have been recorded the daily Martian respectively ground acceleration and pressure. These data are essential to investigate the geophysical and atmospheric features of the red planet. So far, the InSight team were able to detect multiple Martian events. We distinguish two types: the artificial events like the lander modes or the micro-tilts known as glitches or the natural events like the pressure drops which are important to estimate the Martian subsurface and the seismic events used to study the interior structure of Mars. Despite the data complexity, the InSight team was able to catalog these events (Clinton et al 2020 for the seismic event catalog, Banfield et al., 2018, 2020 for the pressure drops catalog and Scholz et al. (2020) for the glitches catalog). However, despite all this effort, we are still in front of multiple challenges. In fact,  the seismic events' detection is limited  due to the SEIS sensitivity, which is the origin of a high noise level that may contaminate the seismic events. Thus, we can miss some of them, especially in the noisy period. Besides, their detection is very challenging and require multiple preprocessing task which is time-consuming. For the pressure drops, the detection method used in Banfield et al.  2020 is limited by a threshold equal to 0.3 Pa. Thus, the rest of pressure drops are not included. Plus, due to lack of energy, the pressure sensor was off for several days. As a result, many pressure drops were missed. As a result, being able to detect them directly on the SEIS data which are, in contrast,  provided continuously, is very important.

In this regard, the aim of this study is to overcome these challenges and thus improve the Martian events detection and provide an updated catalog automatically. For that, we were inspired of one of the main technics used today in data processing and analysis in a complete automatic way: it is the Machine Learning and particularly in our case is the Deep Learning. The architecture used for that is the “Hybrid Recurrent Scattering Neural Network” (Bueno et al 2021)  adapted for Mars

How to cite: Barkaoui, S., Bueno Rodriguez, A., Lognonné, P., De Hoop, M., Sainton, G., Plasman, M., and kawamura, T.: Mars events polyphonic detection, segmentation and classification with a hybrid recurrent scattering neural network using InSight mission data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8940, https://doi.org/10.5194/egusphere-egu22-8940, 2022.

Interplanetary coronal mass ejections (ICMEs) are one of the main drivers for space weather disturbances. In the past,
different machine learning approaches have been used to automatically detect events in existing time series resulting from
solar wind in situ data. However, classification, early detection and ultimately forecasting still remain challenges when facing
the large amount of data from different instruments. We propose a pipeline using a Network similar to the ResUNet++ (Jha et al. (2019)), for the automatic detection of ICMEs. Comparing it to an existing method, we find that while achieving similar results, our model outperforms the baseline regarding GPU usage, training time and robustness to missing features, thus making it more usable for other datasets.
The method has been tested on in situ data from WIND. Additionally, it produced reasonable results on STEREO A and STEREO B datasets
with less input parameters. The relatively fast training allows straightforward tuning of hyperparameters and could therefore easily be used to detect other structures and phenomena in solar wind data, such as corotating interaction regions.

How to cite: Ruedisser, H., Windisch, A., Amerstorfer, U. V., Amerstorfer, T., Möstl, C., Reiss, M. A., and Bailey, R. L.: Automatic Detection of Interplanetary Coronal Mass Ejections, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9077, https://doi.org/10.5194/egusphere-egu22-9077, 2022.

Machine learning (ML) techniques have been successfully introduced in the fields of Space Physics and Space Weather, yielding highly promising results in modeling and predicting many disparate aspects of the geospace. Magnetospheric ultra-low frequency (ULF) waves play a key role in the dynamics of the near-Earth electromagnetic environment and, therefore, their importance in Space Weather studies is indisputable. Magnetic field measurements from recent multi-satellite missions are currently advancing our knowledge on the physics of ULF waves. In particular, Swarm satellites have contributed to the expansion of data availability in the topside ionosphere, stimulating much recent progress in this area. Coupled with the new successful developments in artificial intelligence, we are now able to use more robust approaches for automated ULF wave identification and classification. Here, we present results employing various neural networks (NNs) methods (e.g. Fuzzy Artificial Neural Networks, Convolutional Neural Networks) in order to detect ULF waves in the time series of low-Earth orbit (LEO) satellites. The outputs of the methods are compared against other ML classifiers (e.g. k-Nearest Neighbors (kNN), Support Vector Machines (SVM)), showing a clear dominance of the NNs in successfully classifying wave events.

How to cite: Balasis, G., Antonopoulou, A., Papadimitriou, C., Boutsi, A. Z., Giannakis, O., and Daglis, I. A.: Machine Learning Techniques for Automated ULF Wave Recognition in Swarm Time Series, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9621, https://doi.org/10.5194/egusphere-egu22-9621, 2022.

The solar wind and its variability is well understood at Earth. However, at distances larger than 1AU the is less clear, mostly due to the lack of in-situ measurements. In this study we use transfer learning principles to infer solar wind conditions at Mars in periods where no measurements are available, with the aim of better illuminating the interaction between the partially magnetised Martian plasma environment and the upstream solar wind. Initially, a convolutional neural network (CNN) model for forecasting measurements of the interplanetary magnetic field, solar wind velocity, density and dynamic pressure is trained on terrestrial solar wind data. Afterwards, knowledge from this model is incorporated into a secondary CNN model which is used for predicting solar wind conditions upstream of Mars up to 5 hours in the future. We present the results of this study as well as the opportunities to expand this method for use at other planets.

How to cite: Durward, S.: Forecasting solar wind conditions at Mars using transfer learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10105, https://doi.org/10.5194/egusphere-egu22-10105, 2022.

We propose a new method for automatic detection of solar magnetic tornadoes based on computer vision methods. Magnetic tornadoes are magneto-plasma structures with a swirling magnetic field in the solar corona, and there is also evidence for the rotation of plasma in them. A theoretical description and numerical modeling of these objects are very difficult due to the three-dimensionality of the structures and peculiarities of their spatial and temporal dynamics [Wedemeyer-Böhm et al, 2012, Nature]. Typical sizes of magnetic tornadoes vary from 10² km up to 10⁶ km, and their lifetime is from several minutes to many hours. So far, quite a few works are devoted to their study, and there are no accepted algorithms for detecting solar magnetic tornadoes by machine methods. An insufficient number of identified structures is one of many problems that do not allow studying physics of magnetic tornadoes and the processes associated with them. In particular, the filamentous rotating structures are well delectable only at the limb, while one can only make suppositions about their presence at the solar disk.
Our method is based on analyzing SDO/AIA images at wavelengths 171 Å, 193 Å, 211 Å and 304 Å, to which several different algorithms are applied, namely, the convolution with filters, convolutional neural network, and gradient boosting. The new technique is a combination of several approaches (transfer learning & stacking) that are widely used in various fields of data analysis. Such an approach allows detecting the structures in a short time with sufficient accuracy. As test objects, we used magnetic tornadoes previously described in the literature [e.g., Wedemeyer et al 2013, ApJ; Mghebrishvili et al. 2015 ApJ]. Our method made it possible to detect those structures, as well as to reveal previously unknown magnetic tornadoes.

How to cite: Vorobev, D., Blumenau, M., Fridman, M., Khabarova, O., and Obridko, V.: Automatic detection of solar magnetic tornadoes based on computer vision methods., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11501, https://doi.org/10.5194/egusphere-egu22-11501, 2022.

The large amount of data produced by measurements and simulations of space plasmas has made it fertile ground for the application of classification methods, that can support the scientist in preliminary data analysis. Among the different classification methods available, Self Organizing Maps, SOMs [Kohonen, 1982] offer the distinct advantage of producing an ordered, lower-dimensional representation of the input data that preserves their topographical relations. The 2D map obtained after training can then be explored to gather knowledge on the data it represents. The distance between nodes reflects the distance between the input data: one can then further cluster the map nodes to identify large scale regions in the data where plasma properties are expected to be similar.

In this work, we train SOMs using data from different simulations of different aspects of the heliospheric environment: a global magnetospheric simulation done with the OpenGGCM-CTIM-RCM code, a Particle In Cell simulation of plasmoid instability done with the semi-implicit code ECSIM, a fully kinetic simulation of single X point reconnection done with the Vlasov code implemented in MuPhy2.

We examine the SOM feature maps, unified distance matrix and SOM node weights to unlock information on the input data. We then classify the nodes of the different SOMs into a lower and automatically selected number of clusters, and we obtain, in all three cases, clusters that map well to our a priori knowledge on the three systems. Results for the magnetospheric simulations are described in Innocenti et al, 2021. 

This classification strategy then emerges as a useful, relatively cheap and versatile technique for the analysis of simulation, and possibly observational, plasma physics data.

Innocenti, M. E., Amaya, J., Raeder, J., Dupuis, R., Ferdousi, B., & Lapenta, G. (2021). Unsupervised classification of simulated magnetospheric regions. Annales Geophysicae Discussions, 1-28. 

https://angeo.copernicus.org/articles/39/861/2021/angeo-39-861-2021.pdf

How to cite: Innocenti, M. E., Köhne, S., Hornisch, S., Grauer, R., Amaya, J., Raeder, J., Ferdousi, B., Edmond, J. "., and Lapenta, G.: A versatile exploration method for simulated data based on Self Organizing Maps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12480, https://doi.org/10.5194/egusphere-egu22-12480, 2022.

Generating reliable databases of electron density measurements over a wide range of geomagnetic conditions is essential for improving empirical models of electron density. The Neural-network-based Upper hybrid Resonance Determination (NURD) algorithm has been developed for automated extraction of electron density from Van Allen Probes electric field measurements, and has been shown to be in good agreement with existing semi-automated methods and empirical models. The extracted electron density data has since then been used to develop the PINE (Plasma density in the Inner magnetosphere Neural network-based Empirical) model, an empirical model for reconstructing the global dynamics of the cold plasma density distribution based only on solar wind data and geomagnetic indices.
In this study we re-implement the NURD algorithm in both Python and Matlab, and compare the performance of these implementations to each other and previous NURD results. We take advantage of a labeled training data set now being available for the full duration of the Van Allen Probes mission to train the network and generate an electron density data set for a significantly longer time period. We perform detailed comparisons between this output, electron density produced from Van Allen Probes electric field measurements using the AURA semi-automated algorithm, and electron density obtained from existing empirical models. We also present preliminary results from the PINE plasmasphere model trained on this extended NURD electron density data set.

How to cite: Szabo-Roberts, M., Kume, K., Smirnov, A., Zhelavskaya, I., and Shprits, Y.: Re-implementing and Extending the NURD Algorithm to the Full Duration of the Van Allen Probes Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12830, https://doi.org/10.5194/egusphere-egu22-12830, 2022.

Mercury is the only telluric planet of the solar system, other than Earth, with an intrinsic magnetic field. Thus, the Hermean surface is shielded from the impinging solar wind via the presence of an “Earth-like” magnetosphere. However, this cavity is twenty times smaller than its alike at the Earth. The relatively small extension of the Hermean magnetosphere enables us to model it using global full-kinetic simulation with the aid of modern supercomputers. Such modeling is crucial to interpret, and prepare, the future observations of the ongoing joint ESA-JAXA mission BepiColombo.

The model used in this work is based on three-dimensional, implicit full-PIC simulations of the interaction between the solar wind and Mercury’s magnetosphere (i.e. at 0.3-0.47 AU). This model includes self-consistently the ion and electron physics down to kinetic electron scales. On top of that, we show comparisons between in-situ observations by Mariner-X and BepiColombo space missions. This comparison allows us (i) to validate our model and (ii) to gain insights into the electron dynamics in the Hermean environment, thought to be governed by kinetic-scale processes.

First, we validate our model through a qualitative comparison between three-dimensional outcomes of our global simulations and the ones of reduced fluid/hybrid simulations (in the context of the SHOTS collaboration). Moreover, comparison with in-situ Mariner-X observations during its first Mercury flyby complete the validation of our model. Second, we study the global dynamics of electrons showing regions where strongest particle acceleration/energization occurs, giving quantitative estimate of electron temperature anisotropy in the Hermean environment. Such results are used to interpret past, and plan future, BepiColombo in-situ observations.

How to cite: Lavorenti, F., Henri, P., Califano, F., Deca, J., Aizawa, S., and Andre, N.: Full-kinetic global simulations of the plasma environment at Mercury: a model from planetary to electrons scales to support BepiColombo, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-62, https://doi.org/10.5194/egusphere-egu22-62, 2022.

We analyzed MAVEN observations of fields and plasma signatures associated with an encounter of fully-developed Kelvin–Helmholtz (K–H) vortices at the northern polar terminator along Mars’ induced magnetosphere boundary. The signatures of the K–H vortices event are: (i) quasi-periodic, “bipolar-like” sawtooth magnetic field perturbations, (ii) corresponding density decrease, (iii) tailward enhancement of plasma velocity for both protons and heavy ions, (iv) co-existence of magnetosheath and planetary plasma in the region prior to the sawtooth magnetic field signature (i.e. mixing region of the vortex structure), and (v) pressure enhancement (minimum) at the edge (center) of the sawtooth magnetic field signature. Our results strongly support the scenario for the non-linear growth of K–H instability along Mars’ induced magnetosphere boundary, where a plasma flow difference between the magnetosheath and induced-magnetospheric plasma is expected. Our findings are also in good agreement with 3-dimensional local magnetohydrodynamics (MHD) simulation results. MAVEN observations of protons with energies greater than 10 keV and results from the Walén analyses suggests the possibility of particle energization within the mixing region of the K–H vortex structure via magnetic reconnection, secondary instabilities or other turbulent processes. We estimated the lower limit on the K–H instability linear growth rate to be ~5.84 x 10^-3 s^-1. For these vortices, we estimate the lower limit of the instantaneous atmospheric ion escape flux due to the detachment of plasma clouds during the late non-linear stage of K–H instability to be ~5.90 x 10²⁶ particles/s, which is agrees with earlier studies for the Venusian plasma clouds but ~two orders of magnitude larger than that calculated for Mars. 

How to cite: Poh, G., Espley, J., Nykyri, K., Fowler, C., Ma, X., Xu, S., Hanley, G., Romanelli, N., Bowers, C., Gruesbeck, J., and DiBraccio, G.: On the Growth and Development of Non-linear Kelvin-Helmholtz Instability at Mars: MAVEN Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-169, https://doi.org/10.5194/egusphere-egu22-169, 2022.

Venus’ lack of an intrinsic magnetic field allows the solar wind to closely interact with its atmosphere [1], making it a
prime target for investigating how unmagnetized atmospheric bodies in our Solar System [2] or elsewhere [3] interact
with magnetized plasma flows. This close interaction means that solar-activity correlations exhibited by the solar wind and
other heliospheric parameters [4, 5] cause solar-cycle variations in Venus’ plasma environment and plasma phenomena. We
investigate these variations by characterizing the proton population around Venus during periods of solar minimum (2006–2009)
and maximum (2010–2014). We use data from the Ion Mass Analyser (IMA) instrument, a particle mass-energy spectrometer
which was onboard the Venus Express (VEX) mission. We apply a previously developed methodology which fits Maxwellian
models to measurements of the protons’ velocity distribution functions [6] to produce statistical distributions of bulk speeds and
temperatures in various regions of Venus’ plasma environment. We also present spatial maps and probability-density histograms
comparing the proton parameters between the two time periods.
We find that the temperatures perpendicular (T_⊥) and parallel (T) to the background magnetic field are 20–35% lower
in the magnetosheath during solar maximum. This suggests that the heating of particles as they cross the bow shock varies
between the two time periods. We also find that the regions in the magnetosheath with highest temperature ratio T_⊥/T are
farther downstream from the bow shock during solar maximum than minimum. This is consistent with previous observations of
how mirror-mode structures presumably generated at the bow shock strictly decay as they are convected into the magnetosheath
during solar minimum, whereas during solar maximum they first grow and then decay [7]. We also present ongoing work to
further characterize the plasma environment as a function of upstream solar-wind parameters (such as Mach number or cone
angle) and bow shock geometry. We discuss preliminary results concerning energy conversion processes at Venus’ bow shock.

REFERENCES
[1] Y. Futaana, G. Stenberg Wieser et al., “Solar Wind Interaction and Impact on the Venus Atmosphere,” Space Science Reviews, vol. 212, no. 3-4, 2017.
[2] C. Bertucci, F. Duru et al., The induced magnetospheres of mars, venus, and titan, 2011, vol. 162, no. 1-4.
[3] C. Dong, M. Jin et al., “Atmospheric escape from the TRAPPIST-1 planets and implications for habitability,” Proceedings of the National Academy of
Sciences of the United States of America, vol. 115, no. 2, 2017.
[4] C. T. Russell, E. Chou et al., “Solar and interplanetary control of the location of the Venus bow shock,” Journal of Geophysical Research, vol. 93, no. A6, 1988.
[5] P. R. Gazis, “Solar cycle variation in the heliosphere,” Reviews of Geophysics, vol. 34, no. 3,  1996.
[6] A. Bader, G. Stenberg Wieser et al., “Proton Temperature Anisotropies in the Plasma Environment of Venus,” Journal of Geophysical Research: Space
Physics, vol. 124, no. 5, 2019.
[7] M. Volwerk, D. Schmid et al., “Mirror mode waves in Venus’s magnetosheath: Solar minimum vs. solar maximum,” Annales Geophysicae, vol. 34, no. 11, 2016.

How to cite: Rojas Mata, S., Stenberg Wieser, G., Futaana, Y., Bader, A., Persson, M., Fedorov, A., and Zhang, T.: Proton Temperature Anisotropies in the Venus Plasma Environment during Solar Minimum and Maximum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-653, https://doi.org/10.5194/egusphere-egu22-653, 2022.

In 2020 and 2021 both BepiColombo and Solar Orbiter used Venus for a gravity assist in order to reach Mercury and to finally get into the correct orbit around the Sun, respectively. These flybys were the first since Mariner 10 to sample a long stretch, more than 30 Venus radii of the induced magnetotail of Venus. This brought the opportunity to study the structure and dynamics of the tail during different solar wind conditions. On this poster we will discuss the differences and also the similarities (even though the four flybys took different trajectories through the induced magnetotail) using the magnetometers on both spacecraft. Field line draping, magnetic reconnection, and plasma waves will all pass by on stage.

How to cite: Volwerk, M. and the The VenusMagTeam: Two Spacecraft, Four Flythroughs: Magnetometer Measurements by BepiColombo and Solar Orbiter in the Induced Magnetotail of Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-822, https://doi.org/10.5194/egusphere-egu22-822, 2022.

The Martian interaction with the solar wind leads to the formation of a bow shock upstream of the planet. The shock dynamics appears complex, due to the combined influence of external (solar photons, solar wind plasma and fields) and internal (crustal magnetic fields, ionized atmosphere) drivers. The extreme ultraviolet fluxes and magnetosonic mach number are known major drivers of the shock location, while the influence of other possible drivers is less constrained or unknown such as crustal magnetic fields or the solar wind dynamic pressure and the Interplanetary Magnetic Field (IMF) intensity and orientation.

We analyze and rank the influence of the main drivers of the Martian shock location, based on published datasets from Mars Express and Mars Atmosphere Volatile EvolutioN missions and on several methods such as the Akaike Information Criterion, Least Absolute Shrinkage Selection Operator regression, and partial correlations. We include here the influence of the crustal fields, extreme ultraviolet fluxes, magnetosonic mach number, solar wind dynamic pressure and various Interplanetary Magnetic Field parameters (intensity and orientation angles).

We conclude that the major drivers of the shock location are extreme ultraviolet fluxes and magnetosonic mach number, while crustal fields and solar wind dynamic pressure are secondary drivers at a similar level. The IMF orientation also plays a significant role, with larger distances for perpendicular shocks rather than parallel shocks.

How to cite: Garnier, P., Jacquey, C., Gendre, X., Génot, V., Mazelle, C., Fang, X., Gruesbeck, J., Sanchez-Cano, B., and Halekas, J.: Ranking the drivers of the Martian bow shock location: a statistical analysis of Mars Atmosphere and Volatile EvolutioN and Mars Express observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1609, https://doi.org/10.5194/egusphere-egu22-1609, 2022.

For more than two years, ESA’s Rosetta mission measured the complex and ever-evolving plasma environment surrounding comet 67P/Churyumov-Gerasimenko. In this work, we explore the structure and dynamics of the near-comet plasma environment at steady state, comparing directly the results of a spherically symmetric Haser model and an asymmetric outgassing profile based on the measurements from the ROSINA instrument onboard Rosetta during 67P’s weakly outgassing stages. Using a fully kinetic semi-implicit particle-in-cell code, we are able to characterise (1) the various ion and electron populations and their interactions, and (2) the implications to the mass-loading process caused by taking into account asymmetric outgassing. Our model complements observations by providing a full 3D picture that is directly relevant to help interpret the measurements made by the Rosetta Plasma Consortium instruments. In addition, understanding such details better is key to help disentangle the physical drivers active in the plasma environment of comets visited by future exploration missions.

How to cite: Deca, J., Stephenson, P., Divin, A., Henri, P., and Galand, M.: A Fully Kinetic Perspective on Weakly Active Comets: Symmetric versus Asymmetric Outgassing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1814, https://doi.org/10.5194/egusphere-egu22-1814, 2022.

On August 10, 2021, the Mercury-bound BepiColombo spacecraft flew for the second time by Venus for a Gravity-Assist Maneuver. During this second flyby of Venus, a limited number of instruments were turned on, allowing unique observations of the planet and its environment. Among these instruments, the Mass Spectrum Analyzer (MSA) that is part of the particle analyzer consortium onboard the magnetospheric orbiter (Mio) was able to acquire its first plasma composition measurements in space. As a matter of fact, during a limited time interval upon approach of the planet, substantial ion populations were recorded by MSA, with characteristic energies ranging from about 20 eV up to a few hundreds of eVs. Comparison of the measured Time-Of-Flight spectra with calibration data reveals that these populations are of planetary origin, containing both Oxygen and Carbon ions. The Oxygen observations are to some extent consistent with previous in situ measurements from mass spectrometers onboard Venus Express and Pioneer Venus Orbiter. On the other hand, the MSA data provide the first ever in situ evidences of Carbon ions in the near-Venus environment at about 6 planetary radii. We show that the abundance of C+ amounts to about ~30% of that of O+. Furthermore, the fact that photoelectrons are simultaneously observed with the low energy planetary ions indicate a magnetic connection to the dayside ionosphere from which ions are ejected under the effect of the ambipolar electrostatic field.

How to cite: Hadid, L. and the MSA, MIA and MEA teams: First evidence of carbon escape through Venus magnetosheath along draped magnetic field lines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1821, https://doi.org/10.5194/egusphere-egu22-1821, 2022.

Solar energetic particles (SEPs) are high-energetic particles that consist mainly of electrons and protons with energies from a few tens of keV to GeV ejected  associated with solar flares and coronal mass ejections. SEPs can precipitate into planetary atmospheres cause ionization, excitation and dissociation of atmospheric molecules, leading to changes in atmospheric chemical composition via chemical network [e.g. Solomon et al., 1981; Adams et al., 2021].

The effect of SEPs on ozone concentration in the Earth’s polar region has been intensively studied for the past decades. For instance, during the enormous solar flare that occurred in late October 2003, NO_x and HO_x concentrations were enhanced and ozone concentration was depleted by 40% at the polar lower mesosphere [e.g. Jackman et al., 2005]. Increased ionization and dissociation of atmospheric N₂ and O₂molecules led to the production of NOx and HOx, which catalytically destroyed ozone at the polar mesosphere.

Recently, the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft has discovered global diffuse aurora on the nightside of Mars down to few tens km in altitude during SEP events, indicating that a significant amount of energy could be deposited in the atmosphere deeper than previously thought  [Schneider et al., 2015; Nakamura et al., 2022]. However, the effects of SEPs on the atmospheric chemistry of present-day Mars have not yet been investigated by observations and/or models.

By coupling a Monte Carlo model PTRIP (Nakamura et al., 2022) and a newly developed photochemical model to investigate the effects of SEPs on the atmospheric compositions at Mars, we performed a simulation to track the effects of a large SEP event on the Martian atmospheric composition. We found that HO_x increased by a factor of 10 and ozone decreased by a factor of 10 in the altitude range from 20 km to 60 km. This is the very first estimation of the effects of SEPs on the atmospheric neutral compositions at Mars, indicating that similar effects on HO_x and ozone could be expected on Mars than on Earth.

How to cite: Nakamura, Y., Terada, N., Leblanc, F., Nakagawa, H., Sakai, S., Hiruba, S., Kataoka, R., and Murase, K.: Numerical prediction of the effects of solar energetic particle precipitation on the Martian atmospheric chemical composition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2181, https://doi.org/10.5194/egusphere-egu22-2181, 2022.

The Martian crustal magnetic anomalies create a varied, asymmetric obstacle for the draped interplanetary magnetic field (IMF) to interact with. One possible result of this interaction is magnetic reconnection, a process by which anti-parallel magnetic field lines connect and reconfigure, transferring energy into the surrounding environment and mixing previously separated plasma populations. Here, we present an analysis to determine the draped IMF conditions that favor reconnection with the underlying crustal anomalies at Mars. First, we plot a map of the crustal anomalies’ strength and orientation compiled from magnetic field data taken throughout the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Second, we create “shear maps” which calculate and plot the angle of shear between the transverse component of the anomalies and a chosen overlaid draping direction. Third, we define a “shear index” which quantifies the susceptibility of a particular region to undergo reconnection based on a given draped IMF orientation and the resulting shear map for that region. We then compare the shear index for a variety of draped field orientations within different regions of the Martian magnetosphere. Our results suggest eastward/westward (horizontal) draped fields present regions that are more likely for anti-parallel magnetic reconnection to occur with the crustal anomalies than northward/southward (vertical) draped fields, with one notable exception being the strongest crustal anomalies located in the southern hemisphere ~180° longitude. An east/west draped field roughly corresponds to a +/- B_y IMF direction on the dayside, implying the rate of magnetic reconnection on the dayside of Mars may be enhanced for IMF field lines pointing in the +/- Y_MSO direction compared to that of IMF field lines pointing in the +/- Z_MSO direction, with MSO referring to the Mars Solar Orbital coordinate system. Understanding the interplay between Mars’s crustal magnetic fields and the IMF is crucial to answer outstanding science questions regarding nightside magnetospheric activity at Mars, namely how IMF orientation affects the twisting of the magnetotail, open magnetic topology observations on the nightside, and discrete aurora observations in the southern hemisphere.

How to cite: Bowers, C. F., DiBraccio, G. A., Slavin, J. A., Gruesbeck, J. R., Weber, T., Romanelli, N., Azari, A. R., and Xu, S.: Exploring the solar wind-planetary interaction at Mars: Implication for Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2853, https://doi.org/10.5194/egusphere-egu22-2853, 2022.

We investigate the Venusian magnetotail and its boundaries utilising magnetic field and density measurements that cover a wide range of radial distances, from the two geometrically similar Solar Orbiter Venus flybys on 27 December 2020 and 9 August 2021. We look at the magnetic field components along the spacecraft trajectory in an attempt to identify boundary crossings, as well as the extent and intensity of the bowshock deep in the magnetotail. We compare these observations with results of a simulation of the induced magnetosphere and magnetotail of Venus, where the initial upstream conditions are provided by Solar Orbiter measurements, to examine in what degree the simulation representation agrees with the observations. The model encloses a massive volume of 80R_V x 60R_V x 60R_V  in which we look at magnetic field and proton density variations. Additionally, we vary the rotation of the clock angle in order to find for which rotation angle we get the best match with the observations during the different steps of the spacecraft's trajectory. 

How to cite: Stergiopoulou, K., Jarvinen, R., Andrews, D. J., Edberg, N. J. T., Dimmock, A. P., Kallio, E., and Khotyaintsev, Y.: Solar Orbiter Data-Model Comparison in Venus' Induced Magnetotail, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3658, https://doi.org/10.5194/egusphere-egu22-3658, 2022.

As Venus does not have an intrinsic magnetic field, the solar wind interacts directly with the Venusian atmosphere, altering its structure and composition, for example through atmospheric ion escape to space. In particular, the interaction will result in the formation of plasma boundaries, which separate regions of different plasma populations around Venus. Knowing how space weather influences the shape of these boundaries is one of the key pieces to understanding the current state of the Venusian atmosphere.

During its eight years mission, including more than 3000 orbits around Venus, Venus Express made measurements of the plasma environment, covering a wide range of upstream conditions. Using conjoint plasma and magnetic field measurements from the ASPERA-4 (Analyser of Space Plasma and Energetic Atoms) and the magnetometer instruments, we identified the locations where the spacecraft crossed the bow shock and the ion composition boundary for each orbit. Using the derived dataset, we then determined the boundary shapes with a two-parameter fit. The boundary shape fittings were done with respect to one or multiple upstream conditions.

Here we report that both boundaries are highly dependent on solar wind extreme ultraviolet (EUV) flux, expanding further from the planet at solar maximum. A likely explanation is that at solar maximum, combined heating of the exosphere ions and a higher photoionization rate lead to a higher planetary ion production. These additional ions increase the internal thermal pressure, pushing the boundaries outward.

Additionally, at solar minimum, solar wind parameters like dynamic pressure and energy flux were found to not affect the shape of the bow shock, which is consistent with previous studies. The influence of the strength and orientation of the interplanetary magnetic field, the Mach number, and potential correlations between multiple upstream parameters, are also discussed in this talk.

How to cite: Signoles, C., Persson, M., Wolff, A., Martinez, N., Lindwall, V., Futaana, Y., Rojas-Mata, S., Zhang, T., André, N., Aizawa, S., and Fedorov, A.: Influence of planetary space weather on the shapes of Venus plasma boundaries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4000, https://doi.org/10.5194/egusphere-egu22-4000, 2022.

The 2nd Venus flyby of BepiColombo has been examined and compared by the newly developed global hybrid simulation LatHyS for the Venusian environment. The LatHyS has been first validated by comparison with Venus Express observations, then using the observation from Solar Orbiter, which was located in the upstream region and both observed the same solar wind, it is applied for the Venus flyby. The simulation successfully reproduced the observed signatures and it shows that BepiColombo passed through the stagnation region of Venus, which supports the results obtained by data-analysis. In addition, we have sampled the plasma information along the trajectory and constructed the energy spectrum for three species (solar wind proton, planetary proton, and planetary oxygen ion) and possible effect due to the limited field of view is discussed. Moreover, ion escape from Venus for planetary species have been discussed and the escape rate is estimated. 

How to cite: Aizawa, S., Persson, M., Menez, T., Andre, N., Modolo, R., Barthe, A., Penou, E., Fedorov, A., Sauvaud, J.-A., Leblanc, F., Chaufray, J.-Y., Saito, Y., Yokota, S., Murakami, G., Genot, V., Sanchez-Cano, B., Heyner, D., Horbury, T., Louarn, P., and Owen, C.: LatHyS hybrid simulation of the August, 10 2021 BepiColombo Venus flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4175, https://doi.org/10.5194/egusphere-egu22-4175, 2022.

While space weather has been a growing field of research and applications over the last 15-20 years, “planetary space weather” is an emerging discipline. In fact, as long as we expand our robotic exploration within the solar system, monitoring planetary space weather is becoming more necessary than ever. Despite this, not every spacecraft is designed for plasma science and only a few of them have the necessary plasma instrumentation for space weather purposes. However, all of them have thousands of housekeeping detectors distributed along the spacecraft. In particular, energetic particles impact detectors and subsystems on a spacecraft and their effects can be identified in selected housekeeping data sets, such as the Error detection and correction (EDAC) counters. In this study, we investigate these engineering datasets for scientific purposes by performing the first feasibility study of solar energetic particle detection using EDAC counters from several available ESA Solar System missions, such as Mars Express, Rosetta, BepiColombo and Solar Orbiter. In order to validate the results, these detections are compared to other observations from scientific instruments on board these missions. Moreover, the potential implications of space weather event detections based on EDAC sensors at Mars and Comet 67P/Churyumov-Gerasimenko is analysed. This study has the potential to provide a good network of solar particle observations at locations where no scientific observations of this kind are available.

How to cite: Sanchez-Cano, B., Witasse, O., Knutsen, E. W., Meggi, D., Lester, M., and Wimmer-Schweingruber, R. F. and the ESA mission teams: Space Weather detections with housekeeping sensors onboard Mars Express, Rosetta, BepiColombo and Solar Orbiter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4289, https://doi.org/10.5194/egusphere-egu22-4289, 2022.

We apply a new method, coupling a hybrid plasma model (ions as particles, electrons as a fluid) and measurements from the Mars Atmosphere and Volatile Evolution (MAVEN) mission, to calculate heavy ion escape rates from Mars. With this method, we acquire estimates of the escape rate orbit by orbit in different upstream conditions. We have investigated how the estimated ion escape depends on the assumed composition of heavy ions, the solar wind velocity aberration and the amount of alpha particles in the solar wind. We also estimate the amount of tail escape and radial escape and compare the model results with  recent Mars Express and MAVEN studies.

How to cite: Zhang, Q., Holmström, M., Wang, X., and Fatemi, S.: Estimating heavy ions escape rate from Mars using hybrid model and observations from MAVEN, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4455, https://doi.org/10.5194/egusphere-egu22-4455, 2022.

We study the solar wind interactions of Mercury, Venus and Mars in a global hybrid model, where ions are treated as particles and electrons form a charge-neutralizing fluid. We concentrate on the formation of large-scale, ultra-low frequency (ULF) waves in planetary ion foreshocks and their dependence on solar wind and interplanetary magnetic field conditions in the inner solar system. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is small enough. The magnetic connection to the bow shock allows the backstreaming of solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter bow shock and transmit in the downstream region. The analyzed simulation runs use more than two hundred simulation particles per cell on average to allow fine enough velocity space resolution for resolving the foreshocks and waves self-consistently. We find significant differences in wave and foreshock properties between these three planets and discuss their causes.

How to cite: Jarvinen, R., Kallio, E., and Pulkkinen, T.: Global hybrid modeling of ultra-low frequency solar wind foreshock waves at Mercury, Venus and Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5255, https://doi.org/10.5194/egusphere-egu22-5255, 2022.

Mirror mode structures arise whenever a temperature anisotropy is present in the plasma, classically in the wake of the bow shock in a quasi-perpendicular configuration with respect to the interplanetary magnetic field, or from pickup ion distribution effects. Born from space plasma instabilities and in competition with other wave modes, these ultra-low frequency waves contribute to energy exchanges between the different plasma populations present in the magnetosheath. At Mars and Venus, such structures have very similar scales: they last typically a few tens of seconds and appear as peaks or dips in the magnetic field data in antiphase with the local plasma density variations. As magnetometers are present on many space missions, magnetic field-only criteria are an ideal tool to study these structures across different magnetosheath environments. We present here for the first time a comparison of the statistical occurrence of magnetosheath mirror mode-like structures at Mars with MAVEN and at Venus with Venus Express. Based on magnetic field-only measurements, we use identical detection criteria at both planets to select quasi-linear structures in B-field measurements. We then present two-dimensional maps of mirror mode-like occurrence rates with respect to solar cycle variations and EUV flux levels, atmospheric seasons (for Mars) and the nature of the shock crossing (quasi-parallel or quasi-perpendicular configurations), and compare them between planets. Finally, we discuss ambiguities in the nature of the detected structures and their global effects on the magnetosheath.

How to cite: Simon Wedlund, C., Volwerk, M., Mazelle, C., Rojas Mata, S., Stenberg Wieser, G., Mautner, D., Halekas, J., Espley, J., Rojas-Castillo, D., Möstl, C., and Bertucci, C.: Mirror mode-like structures around unmagnetised planets: a comparison between the magnetosheaths of Mars and Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5413, https://doi.org/10.5194/egusphere-egu22-5413, 2022.

The Rosetta spacecraft orbited the comet 67P/Churuymov-Gerasimenko for approximately two years, primarily remaining close to the nucleus, unlike previous cometary flyby missions. The combination of Rosetta's close orbit and comet 67P's relatively low cometary activity make detections of the bow shock difficult. However, magnetosheath-like proton distributions have been observed, indicating Rosetta indeed was downstream of a bow shock, during periods of higher cometary activity. Here, we search the Ion Composition Analyzer (ICA) data for additional evidence of the cometosheath, the region downstream of the bow shock analogous to a magnetosheath. We examine the proton velocity distributions for high time and spatial variability that is not correlated with changes in the electric or magnetic fields. We present an overview of cometosheath detections and a discussion of the relation between the cometosheath and bow shock properties. Other work shows that the electric potential of the solar wind can be retrieved from the differential slowing of the solar wind species, so we compare time periods with a high electric potential to cometosheath detections, as a high potential can also indicate shock formation.

How to cite: Williamson, H., Nilsson, H., Stenberg Wieser, G., and Moeslinger, A.: Cometosheath observations around comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5627, https://doi.org/10.5194/egusphere-egu22-5627, 2022.

During Rosetta’s 2-year observation period of comet 67P/Churyumov-Gerasimenko, the Ion Composition Analyser (ICA) continuously measured the plasma environment around the comet. The interaction of the solar wind with the cometary plasma and the evolution of the observed solar wind over the course of the mission has been subject of previous studies. It usually shows a single proton population with a large anti-sunward component that gets more and more deflected when the comet approaches perihelion. 

In this study we focus on ICA data obtained during the 19th of April 2016, where we detected two clear peaks in the energy spectra of the proton population. For the level of cometary activity during this time period, a few months after perihelion, a deflected single population is characteristic for the solar wind protons. We attempt to separate these two observed proton populations in the mass-separated ICA data. We then analyse selected plasma properties of the two populations, such as flow velocity (magnitude and direction) and temperatures. This dual proton population is sporadically observed throughout the day, but is otherwise uncommon during the mission. We want to study how these occurrences are related to changes in the cometary environment and the interaction with the solar wind.

A previous study has shown that the difference in proton and alpha particle velocity downstream of a shock can be used to estimate the electrostatic potential of the observation point relative to the solar wind. We take a look on how to interpret the electrostatic potential estimate using the newly estimated proton velocities of both populations.

How to cite: Moeslinger, A., Nilsson, H., Stenberg Wieser, G., and Williamson, H.: Observation of dual proton populations by the Rosetta Ion Composition Analyser, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5648, https://doi.org/10.5194/egusphere-egu22-5648, 2022.

 Rosetta followed comet 67P at heliocentric distances from 1.25 to 3.6 au. The solar wind was observed for much of this time, but significantly deflected and to some extent slowed down by the interaction with the coma. A method is derived to reconstruct the upstream solar wind from H⁺ and He²⁺ observations. The method is based on the assumption that the comet - solar wind interaction can be described by an electric potential that is the same for both H⁺ and He^2+. The reonstructed speed is compared to estimates from the Tao model, as well as OMNI and Mars Express data propagated to the observation point. The reconstruction agrees well with the Tao model for most of the observations, in particular the statistical distribution of solar wind speed. The electrostatic potential relative to the upstream solar wind is derived and shows values from a few tens of V at large heliocentric distances to about 1 kV during solar events and close to perihelion. Reconstructed values of the solar wind for periods of high electrostatic potential are also in good agreement with propagated observations and model results. The Tao model captures some slowing down of high speed streams as compared to observations at Earth or Mars. At low solar wind speeds, below 400 km/s, agreement is better between our reconstruction and Mars observations than with the Tao model. The magnitude of the reconstructed electrostatic potential is a good measure of the slowing down of the solar wind at the observation point.

How to cite: Nilsson, H., Möslinger, A., Williamson, H., Bergman, S., and Stenberg Wieser, G.: Reconstruction of the upstream solar wind at comet 67P, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5973, https://doi.org/10.5194/egusphere-egu22-5973, 2022.

Recent spacecraft observations have revealed the averaged global morphology of the magnetospheric current system of Mars. This current system is generated by the induction of the interplanetary magnetic field and the motional electric field of the solar wind. It couples the ionosphere below and the solar wind above and determines the distribution of the energy inputs from the fast-moving solar wind to the planetary atmospheric ions.

We use Amitis, a GPU-based hybrid (particle ions and fluid electrons) numerical model to study the current system. Under the typical space environment condition, we successfully reproduce the morphology of the observed current system, including the bow shock current, the induced magnetospheric boundary current, and the ionospheric current.

With the full information provided by the model, we can calculate the inner product of the electric field intensity and the current density for any location in the simulation domain. Furthermore, we can separate the currents due to solar wind and planetary ions, and separate the electric field terms caused by different mechanisms, thereby clarifying the contribution of different mechanisms to the ion escape in the solar wind interaction with Mars. 

How to cite: Wang, X. and Fatemi, S.: Global Current System of Martian Induced Magnetosphere: a Hybrid View, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6298, https://doi.org/10.5194/egusphere-egu22-6298, 2022.

The current work investigates the Venusian solar-wind-induced magnetosphere at a high spatial resolution using all Venus Express (VEX) magnetic observations through an unbiased statistical method. We first evaluate the predictability of the interplanetary magnetic field (IMF) during VEX's Venusian magnetospheric transits and then map the induced field in a cylindrical coordinate system under different IMF conditions. Our mapping resolves structures on various scales, ranging from the ionopause to the classical IMF draping. We also resolve two recently reported structures, a low-ionosphere magnetization over the terminator, and a global "looping" structure in the near magnetotail. In contrast to the reported IMF-independent cylindrical magnetic field of both structures, our results illustrate their IMF dependence. In both structures, the cylindrical magnetic component is more intense in the hemisphere with an upward solar wind electric field (E^SW) than in the opposite hemisphere. Under downward E^SW, the looping structure even breaks, which is attributable to an additional draped magnetic field structure wrapping toward −E^SW. In addition, our results suggest that these two structures are spatially separate. The low-ionosphere magnetization occurs in a very narrow region, at about 88°–95° solar zenith angle and 185–210 km altitude. A least-squares fit reveals that this structure is attributable to an antisunward line current with 191.1 A intensity at 179 ± 10 km altitude, developed potentially in a Cowling channel.

How to cite: He, M., Vogt, J., Dubinin, E., Zhang, T., and Rong, Z.: Spatially Highly Resolved Solar-wind-induced Magnetic Field on Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6696, https://doi.org/10.5194/egusphere-egu22-6696, 2022.

During the last decade, MAVEN space mission have emphasized a widespread spatial distribution of escaping O+ ions (Brain et al., 2015; Dong et al., 2015; Curry et al., 2015). Statistical studies have demonstrated that such structure is constant and present an asymmetry with respect to the solar wind convective electric field direction. In the Mars Solar Ecliptic coordinate system, continuous large O+ ion fluxes have been observed from the Martian wake to the Northward hemisphere. Global hybrid models have been developed since more than fiffteen years (Modolo et al., 2005, 2016; Brecht and Ledvina, 2006; Kallio et al., 2006) predicting and reproducing successfully the main characteristics of these escaping ion signatures. To further characterize this heavy-ion escape and its variability due to the solar wind forcing, global hybrid simulations have been performed with different set of upstream solar wind parameters. The impact of the solar wind drivers on the dynamics of O+ ion fluxes are reported and compared to the statistical ion fluxes maps derived from MAVEN/STATIC observations (Dong et al., 2015).

Brain, D. A., McFadden, J. P., Halekas, J. S., Connerney, J. E. P., Bougher, S. W., Curry, S., et al. (2015). The spatial distribution of planetary ion fluxes near Mars observed by MAVEN. Geophys. Res. Lett. 42, 9142–9148. doi:10.1002/2015GL065293

Dong, Y., Fang, X., Brain, D. A., McFadden, J. P., Halekas, J. S., Connerney, J. E., et al. (2015). Strong plume fluxes at Mars observed by MAVEN: An important planetary ion escape channel. Geophys. Res. Lett. 42, 8942–8950. doi:10.1002/2015GL065346

Curry, S. M., Luhmann, J. G., Ma, Y. J., Dong, C. F., Brain, D., Leblanc, F., et al. (2015). Response of Mars O+ pickup ions to the 8 March 2015 ICME: Inferences from MAVEN data-based models. Geophys. Res. Lett. 42, 9095–9102. doi:10.1002/2015GL065304

Modolo, R., Chanteur, G. M., Dubinin, E., and Matthews, A. P. (2005). Influence of the solar EUV flux on the Martian plasma environment. Annales Geophysicae 23, 433–444. doi:10.5194/angeo-23-433-2005

Brecht, S. H. and Ledvina, S. A. (2006). The Solar Wind Interaction With the Martian Ionosphere/Atmosphere 126, 15–38. doi:10.1007/s11214-006-9084-z

Kallio, E., Fedorov, A., Budnik, E., Sa¨les, T., Janhunen, P., Schmidt, W., et al. (2006). Ion escape at Mars: Comparison of a 3-D hybrid simulation with Mars Express IMA/ASPERA-3 measurements 182, 350–359. doi:10.1016/j.icarus.2005.09.018

How to cite: Modolo, R., Leblanc, F., Chaufray, J.-Y., Romanelli, N., Dubinin, E., Génot, V., Baskevitch, C., Brain, D., Curry, S., and Lillis, R.: Modeling the variability of Martian O+ ion escape due to Solar Wind forcing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7665, https://doi.org/10.5194/egusphere-egu22-7665, 2022.

               Galilean moons are embedded in Jupiter’s giant magnetosphere. The Jovian plasma particles interact with the atmosphere of the moons, exchanging momentum and energy, and generate different phenomena such as aurora, electric current, etc.

The exploration of the Galilean moons, and in particular Ganymede and Europa, considered as potential habitats, are listed among the main objectives of the ESA JUpiter ICy moon Explorer (JUICE) mission. In preparation for future observations, a modelling effort is conducted to describe the Europa moon-magnetosphere system.

               We have used the LATMOS Hybrid Simulation (LatHyS) model to characterize the Jovian plasma and magnetic field interaction with the moon and its atmosphere. The model is a hybrid 3D, multi-species and parallel simulation model which is based on a kinetic description of ions and a fluid description of electrons. The model is based on the CAM-CL algorithm and various physical processes has been implemented to describe the solar wind (or a magnetospheric plasma) interaction with Mars, Mercury, Titan, Ganymede, Earth-like body etc… (Matthews, 1994, Modolo et al, 2016, Richer et al, 2012, Modolo et al, 2008, Leclercq et al, 2015, Turc et al, 2015).  This simulation model depicts the dynamic and the structure of the ionized environment in the neighborhood of these bodies. Recently, the model has been adapted to Europa-Jupiter interaction. Global simulation results are compared to Galileo observations and will be used to illustrate the conditions that JUICE might encounter during its flybys.

         
References :

Alan P. Matthews, Current Advance Method and Cyclic Leapfrog for 2D Multispecies Hybrid Plasma Simulations, Journal of Computational Physics, Volume 112, Issue 1, 1994, Pages 102-116, ISSN 0021-9991, https://doi.org/10.1006/jcph.1994.1084.

Turc L., Fontaine D., Savoini P., Modolo R., 3D hybrid simulations of the interaction of a magnetic cloud with a bow shock, JGR, 2015

Richer E, Modolo R, Chanteur GM, Hess S and Leblanc F, A Global Hybrid Model for Mercury's Interaction With the Solar Wind: Case Study of the Dipole Representation, Journ. Geophys. Res., doi:10.1029/2012JA017898, 2012

Leclercq L., Modolo R., Leblanc F., Hess S., Mancini M. ,3D Magnetospheric parallel hybrid multi-grid method applied to planet-plasma interactions, Journal of Computational Physics, 309, pp.295-313, 10.1016/j.jcp.2016.01.005, 2016

Modolo R., Hess S., Mancini M., Leblanc F., Chaufray J.-Y., Brain D., Leclercq L., Esteban Hernandez R., Chanteur G., Weill P., Gonzalez-Galindo F. et al., Mars-solar wind interaction: LatHyS, an improved parallel 3-D multispecies hybrid model, Journal of Geophysical Research : Space Physics, American Geophysical Union/Wiley, 2016, 121 (7), pp.6378-6399.10.1002/2015JA022324, 2016

How to cite: Baskevitch, C.-A., Modolo, R., and Cecconi, B.: Europa’s interaction with the Jovian plasma from hybrid simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7692, https://doi.org/10.5194/egusphere-egu22-7692, 2022.

Induced magnetospheres of non-magnetized atmospheric bodies like Mars and Venus are formed by magnetic fields of ionospheric currents induced by the convective electric field E = - V x B/c of the solar wind. When the interplanetary magnetic field is mostly radial (the cone angle θ is close to 0°, quasi-parallel conditions) and the convective field E ≈ 0, an induced magnetosphere becomes degenerate. The degenerate induced magnetospheres can be considered as a specific type of the interaction with ambient plasma. This type of interaction were observed at Venus and Mars, for example, 12 observed cases for Venus and 17 observed cases for Mars for θ < 10° as recorded by Venus Express (2006-2014) and Mars express (2014-2019). However, the quasi-parallel conditions are nominal for the majority of discovered exoplanets (hot Jupiters) orbiting the parent stars on distances 0.01 – 0.1 au when θ < 4° (assuming the solar conditions). The conditions at some moons of icy giants, Neptune (Triton) and Uranus, are also quasi-parallel due to large angle between magnetic dipole and the rotation axis though the plasma flow is subsonic.

In this report we introduce degenerate induced magnetospheres as a new type of interaction and review the current works on the subject. We also show examples of observations at Mars and Venus and numerical simulations, and describe the main properties and basic physics of such configurations.

How to cite: Barabash, S., Holmström, M., Yoshifumi, F., Zhang, Q., and Ramstad, R.: Degenerate induced magnetospheres, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7952, https://doi.org/10.5194/egusphere-egu22-7952, 2022.

The magnetosheath is defined as the plasma region between the bow shock, where the super-magnetosonic solar wind plasma is decelerated and heated, and the outer boundary of the intrinsic planetary magnetic field, the so-called magnetopause. Recently we  presented an analytical magnetosheath plasma flow model around Mercury, which can be used to estimate the plasma flow magnitude and direction at any given point in the magnetosheath exclusively on the basis of the plasma parameters of the upstream solar wind. However, this model assumes a constant plasma density and velocity along the flowlines. Here we present a more sophisticated model were we take hydrodynamic effects into account, to also obtain the density and velocity change along the flowline. The model serves as a useful tool to trace the magnetosheath plasma along the streamline both in a forward sense (away from the shock) and a backward sense (toward the shock), offering the opportunity of studying the growth or damping rate of a particular wave mode or evolution of turbulence energy spectra along the streamline in view of upcoming arrival of BepiColombo at Mercury.

How to cite: Schmid, D., Narita, Y., Plaschke, F., Volwerk, M., Nakamura, R., and Baumjohann, W.: A magnetosheath hydrodynamic plasma flow model around Mercury, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8557, https://doi.org/10.5194/egusphere-egu22-8557, 2022.

Mars Express and MAVEN observations have demonstrated the influence of Mars’s spatially variable crustal magnetic fields upon the configuration of the plasma in the ionosphere. This influence furthermore leads to variations in ionospheric escape, conceivably in part through the modification of the plasma density and electron temperature in the upper ionosphere. However, quantifying this control remains challenging given the generally dynamic and spatially varied nature of the Mars solar wind interaction, and the therefore naturally varying densities and temperatures of the upper ionosphere in particular. In this study we examine MAVEN Langmuir Probe and Waves data, finding a very clear correspondence between the structure of the crustal fields and both the measured electron temperatures and densities, by first constructing a robust “average” profile from which departures can be quantified. Electron temperatures are shown to be systematically lower in regions of strong crustal fields over a wide altitude range, as has been previously reported. Here, we additionally use measurements made by MAVEN in the solar wind, to explore the dependence of this crustal field control on the coupling to the solar wind and IMF.  We also attempt to quantitatively determine the altitude range over which this coupling between plasma density and temperature and crustal fields is effective.

How to cite: Andrews, D., Andersson, L., Ergun, R., Eriksson, A., Pilinski, M., and Stergiopoulou, K.: Martian crustal magnetic fields and their control of ionospheric plasma densities and temperatures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8569, https://doi.org/10.5194/egusphere-egu22-8569, 2022.

Analysis of nightside nadir-viewing observations taken by MAVEN's Imaging Ultraviolet Spectrograph instrument has identified nearly 200 discrete aurora emissions.  Discrete aurora are sporadic localized ultraviolet emissions originating in the upper Martian atmosphere that occur brightest and most frequently near regions of strong crustal magnetic field strength.  The emission detections were verified and characterized by visual appearance across the disk and spectral analysis of Cameron band and ultraviolet doublet emissions.  No geographic or magnetic field information was used to determine whether a suspected emission was real or an artifact in the data.   Unlike limb observations, nadir observations have no line-of-sight ambiguity, allowing us to locate the emissions with high geographic accuracy.  Nadir viewing also provides global coverage of the nightside disk, giving broad geographic and local time coverage.  We find the same dependence on local time, crustal field strength and interplanetary magnetic field orientation seen in limb observations (Schneider et. al. 2021).  

How to cite: Schneider, N., Johnston, B., Jain, S., Milby, Z., Bowers, C., Dibraccio, G., Gérard, J.-C., and Soret, L.: Discrete Aurora on Mars: Insights into reconnection?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9415, https://doi.org/10.5194/egusphere-egu22-9415, 2022.

Against expectations, the Rosetta spacecraft was able to observe protons of solar wind origin in the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko. This study investigates these unexpected observations and gives a working hypothesis on what could be the underlying cause.

The cometary plasma environment is shaped by two distinct plasma populations: the solar wind, consisting of protons, alpha particles, electrons and a magnetic field, and the cometary plasma, consisting of heavy ions such as water ions or carbon dioxide ions and electrons.

As the comet follows its orbit through the solar system, the amount of cometary ions that is produced varies significantly. This means that the plasma environment of the comet and the boundaries that form there are also dependent on the comet's heliocentric distance.

For example, at sufficiently high gas production rates (close to the Sun) the protons from the solar wind are prevented from entering the inner coma entirely. The region where no protons (and other solar wind origin ions) can be detected is referred to as the solar wind ion cavity.

A second example is the diamagnetic cavity, a region very close to the nucleus of the comet, where the interplanetary magnetic field, which is carried by the solar wind electrons, cannot penetrate the densest part of the cometary plasma.

The Rosetta mission clearly showed that the solar wind ion cavity is larger than the diamagnetic cavity at a comet such as 67P/Churyumov-Gerasimenko. However, this new study finds that in isolated cases, ions of solar wind origin (mostly protons, but also helium) can be detected inside the diamagnetic cavity. We present the observations pertaining to these events and list and discard possible mechanisms that could lead to the solar wind cavity becoming permeable to protons, moving inside the diamagnetic cavity or vanishing entirely. Only one mechanism cannot be discarded: that of a solar wind configuration where the solar wind velocity is aligned with the magnetic field. We show evidence that fits this hypothesis as well as solar wind models in support.

How to cite: Goetz, C., Scharré, L., Simon Wedlund, C., Nilsson, H., Odelstad, E., Taylor, M., and Volwerk, M.: Protons in the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9911, https://doi.org/10.5194/egusphere-egu22-9911, 2022.

Electric field measurements from cometary environments are very rare, but can provide important information on how plasma waves help fashion the plasma environment. We investigate the plasma wave activity observed in the electric field measurements obtained by the Langmuir probe instrument (RPC-LAP) onboard ESA's Rosetta spacecraft, which followed the comet 67P/Churyumov-Gerasimenko in its orbit around the sun for over two years in 2014-2016. We focus on waves in the range 1-30 Hz, roughly corresponding to the lower-hybrid frequency range. Here, electric field oscillations close to the local H₂O⁺ lower hybrid frequency are common. Especially large wave amplitudes are often observed at or near pronounced plasma density gradients, and a linear instability analysis shows that conditions are often favourable for wave growth by the lower hybrid drift instability. However, the association to density gradients is not ubiquitous and other instabilities are likely needed as well to explain the observed wave activity, e.g. the two-stream instability between solar wind protons and cometary pick-up ions. Close to peak activity of the comet however, the solar wind flow was entirely diverted and excluded from the inner parts of the coma, where the spacecraft was. Here, we instead propose that an ion/ion streaming instability between cold newborn cometary ions and heated heavy ions that were picked up earlier, plays an important role for generating the waves observed in the lower hybrid frequency range. We compare theoretical conditions for growth of these instabilities to observed conditions in the plasma at 67P. This investigation helps to clarify the role and importance of these plasma waves in the cometary plasma environment. They can, for example, heat or cool plasma populations, produce supra-thermal electrons, reduce plasma anisotropies and gradients, couple different plasma species, and provide anomalous resistivity.

How to cite: Odelstad, E., Eriksson, A., and Karlsson, T.: Lower-Hybrid waves observed by Rosetta at comet 67P, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10492, https://doi.org/10.5194/egusphere-egu22-10492, 2022.

Measurements of Energetic Neutral Atoms (ENAs) provide information about both the plasma and neutral components along the line-of-sight for any ENA instrument, though the individual influences of the plasma and neutral environments are convoluted due to the nature of the charge-exchange ENA generation process. We combine ion flux and magnetic field measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter at Mars with models for the Martian exospheric components to predict the average observable 10 eV – 10 keV oxygen and hydrogen ENA distributions from virtual orbits in the near-Mars space environment. The predicted distributions are consistent with past ENA measurements, informing and constraining future ENA investigations of the neutral and plasma near-Mars space environments.

How to cite: Ramstad, R., Brain, D., Dong, Y., Halekas, J., McFadden, J., Espley, J., and Jakosky, B.: Energetic Neutral Atoms at Mars: Predicted Distributions Based on MAVEN Measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10876, https://doi.org/10.5194/egusphere-egu22-10876, 2022.

Menura, a  newly developped hybrid PIC code, allows the self-consistent simulation between a turbulent upstream flow and an obstacle. A global view of such interactions is a novel product which allows us to diagnose both the impact of the additional turbulent energy on the obstacle, and the evolution of the turbulence when processed by planetary boundaries. We present the examples of exospheres (comets, at various heliocentric distances) and ionospheres (Mars-like obstacle). We find that the boundaries are changed in size, and present a much more dynamic behaviour. New plasma structures appear within the magnetospheres due to the impinging perpendicular magnetic field fluctuations, piling up and draping around the dense ionospheres/exospheres (see Figure). The spectral content is also extracted from within the magnetospheres, providing a strong comparison point with experimental studies of magnetospheric turbulence.

How to cite: Behar, E. and Henri, P.: Simulating the interaction between a turbulent solar wind and bodies of the solar system., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13021, https://doi.org/10.5194/egusphere-egu22-13021, 2022.

Cosmogenic radionuclides concentrations are predominantly determined by the solar activity and space weather around the Earth, forming an important source of cosmic-origin background radiation in the terrestrial environment. The highest values of such radiation are observed during the solar minima because the penetrability of the Earth’s magnetosphere is greatest at that time. Beryllium ⁷Be binds to aerosols and is transported within a few years to the Earth’s surface. Its concentrations are higher during the spring and summer months when the stratospheric ⁷Be penetrates the troposphere as a result of the exchange of air masses between the troposphere and stratosphere. We compare periods of strong solar and geomagnetic storms with periods of very low solar activity in the longitudinal view during the years 1986 – 2020.

For a better understanding of the process dynamics, in our work we investigate the coupling of concentrations of the cosmogenic radionuclide ⁷Be (time series of activity concentration of ⁷Be in aerosols) to space weather parameters around the Earth (Kp planetary index, disturbance storm time Dst, proton density, proton flux), proxy parameters of the solar activity (intensity of solar radio flux, relative sunspot number), stratospheric dynamics parameters (temperature, zonal component of wind, O₃), and aggregates of strong atmospheric frontal transition. The beryllium radionuclide ⁷Be concentration was evaluated by the corresponding activity in aerosols on a weekly basis at the National Radiation Protection Institute Monitoring Section in Prague.

We also perform the case study of cosmogenic radionuclide ⁷Be concentrations during the period of strong solar and geomagnetic storm in November 2021 with the ERA5 reanalysis data, and Aeolus satellite lidar wind measurements.

How to cite: Podolská, K., Kozubek, M., Hýža, M., and Šindelářová, T.: The effect of space weather, proxy parameters of solar activity, and stratospheric phenomena on the concentration of cosmogenic radionuclide 7Be (in the Czech Republic), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4659, https://doi.org/10.5194/egusphere-egu22-4659, 2022.

Galactic cosmic rays (GCRs) consist of energetic electrons and nuclei which are a direct sample of material from far beyond the solar system. Measurements by various particle detectors have shown that the intensity varies on different timescales, caused by the Sun’s activity and geomagnetic variation. Interplanetary disturbances cause space weather effects which warrant a more detailed study. Many studies on GCR intensity decreases is based on the analysis of ground-based neutron monitors and muon telescopes. Their measurements depend on the geomagnetic position, and the processes in the Earth's atmosphere. In order to get a better understanding of the geomagnetic filter over the solar cycle, the Christian-Albrechts-Universität zu Kiel, DESY Zeuthen, and the North-West University in Potchefstroom, South Africa agreed on a regular monitoring of the GCR intensity as a function of latitude, by installing a portable device aboard the German research vessel Polarstern in 2012. The vessel is ideally suited for this research campaign because it covers extensive geomagnetic latitudes (i.e. goes from the Arctic to the Antarctic) at least once per year. Here we present the measurements for different latitude surveys including the periods of solar maximum in 2014 and solar minimum in 2019. 

The Kiel team received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405. The team would like to thank the crew of the Polarstern and the AWI for supporting our research campaign.

How to cite: Heber, B., Banjac, S., Burmeister, S., Zoska, M., Giese, H., Herbst, K., Romaneehsen, L., Schwerdt, C., Stauss, D., Wallmann, C., Vogt, A., and Walter, M.: Measurements of cosmic rays by a mini neutron monitor aboard the German research vessel Polarstern., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5539, https://doi.org/10.5194/egusphere-egu22-5539, 2022.

Water availability is a key challenge in agriculture, especially given the expected increase of droughts related to climate change. Soil moisture (SM) sensors can be used to collect information on water availability in a reliable and accurate way. However, due to their very small measuring volume, the installation of multiple sensors is required. In addition, in-situ sensors may need to be removed during field management and connecting cables are often damaged by rodents and other wilderness animals. Hence, the demand for SM sensors that do not have such limitations will increase in the upcoming years. A promising non-invasive technique to monitor SM is cosmic-ray neutron sensing (CRNS), which is based on the negative correlation between fast neutrons originating from cosmic radiation and SM content. With its large measuring footprint of ~130-210m, CRNS can efficiently cover the field-scale. However, heterogeneous agricultural management (e.g., irrigation) can lead to abrupt SM differences, which pose a challenge for the analysis of CRNS data. Here, we investigate the effects of small-scale soil moisture patterns on the CRNS signal by using both modelling approaches and field studies. The neutron transport model URANOS was used to simulate the neutron signal of a CRNS station located in irrigated plots of different sizes (from 1 to 8 ha) with different soil moisture (from 5 and 50 Vol.%) inside and outside such a plot. A total of 400 different scenarios were simulated and the response functions of multiple detector types were further considered. In addition, two CRNS with Gadolinium shielding were installed in two irrigated apple orchards of ~1.2 ha located in the Pinios Hydrologic Observatory (Greece) in the context of the H2020 ATLAS project. Reference soil moisture was determined using 25 SoilNet stations, each with 6 SM sensors installed in pairs at 5, 20 and 50 cm depth and water potential sensors at 20 cm depth. The orchards were also equipped with two Atmos41 climate stations and eight water meters for irrigation monitoring. The CRNS were calibrated using either soil samples or the SM measured by the SoilNet network. In the URANOS simulations, the percentage of neutrons detected by the CRNS that are representative of an irrigated plot varied between 45 and 90% and was strongly influenced by both the dimension and SM of the irrigated plot. As expected, the CRNS footprint decreased considerably with increasing SM but did not appear to be influenced by the plot dimension. SM variation within the irrigated plot strongly affected the neutron energy at detection, which was not the case for SM variations outside the plot. The instrumented fields corroborated the URANOS findings and the performance of the local CRNS was dependent on a) the timing and intensity of irrigation and precipitation, b) the CRNS calibration strategy, and c) the management of the surrounding fields. These results provide novel and meaningful information on the impact of horizontal SM patterns on CRNS measurements, which will help to make CRNS more useful in irrigated agriculture.

How to cite: Brogi, C., Bogena, H. R., Köhli, M., Hendricks Franssen, H.-J., Dombrowski, O., Pisinaras, V., Chatzi, A., Babakos, K., Jakobi, J., Ney, P., and Panagopoulos, A.: Challenges and solutions for cosmic-ray neutron sensing in heterogeneous soil moisture situations related to irrigation practices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6238, https://doi.org/10.5194/egusphere-egu22-6238, 2022.

Neutrons on Earth interact with the soil and are substantially moderated by hydrogen atoms. Since the reflected neutron flux is a function of the soil water content, cosmic-ray neutron measurements above the ground can be used to estimate the average field soil moisture. Thus, if the local incoming neutron flux and the abundance of nearby hydrogen pools are known, the reflected neutron flux could be modeled and compared to observed detector count rates. However, the incoming neutrons are secondaries produced by interacting energetic Galactic Cosmic Rays (GCRs) in the atmosphere. The total neutron flux on the ground depends on the solar modulation-dependent GCR flux, the geomagnetic position, and the altitude within the atmosphere. So far, measurements of either the Jungfraujoch neutron monitor (NM) or a NM of similar cutoff rigidity have been used and altered to estimate the neutron flux at the position of each neutron detector. In this contribution we present a new method based on the Dorman function to directly compute the local neutron flux using remote neutron monitor data.

We received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 870405

How to cite: Giese, H., Heber, B., Herbst, K., and Schrön, M.: Utilizing Cosmic Ray data as input for neutron-based soil moisture measurement, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6430, https://doi.org/10.5194/egusphere-egu22-6430, 2022.

Abstract

High energy Cosmic Ray (CR) particles are capable of ionizing the Earth’s atmosphere, which leads to changes in the atmospheric physical and chemical properties. One of the most important effects of interactions between the CR particles and atmospheric molecules is the formation of aerosol and its subsequent condensation nuclei processes. These interactions are known with considerable uncertainty yet and may translate into even bigger uncertainties in future climate predictions. Laser Detection and Ranging (LIDAR) is currently the best suited technology to retrieve aerosol optical and microphysical properties is also used for the atmosphere correction of high energy cosmic ray observatory data. LIDAR measurements are available from single stations or from networks at continental scale like the European Aerosol Research LIdar NETwork (EARLINET). Sun photometer data are the most suitable complement to LIDAR measurements for the study of aerosol properties due to the extensive coverage of their measurements available through the AErosol RObotic NETwork (AERONET) network. The purpose of this study is to find the correlation between the aerosol properties and the CR data. The aerosol properties retrieved from two databases for the period of 2016-2020: I) the multi-wavelength LIDAR system Potenza EArlinet Raman Lidar (PEARL) which operates at the CNR-IMAA (Tito Scalo (Italy) and contributes to the EAELINET); and II) the AERONET sun photometer data from the stations located at Southern Italy i.e. Potenza (40.60° N, 15.72° E, 820m), Naples (40.83° N, 14.30° E, 50 m) and Lecce (40.33° N, 18.11° E, 30m). whereas, the CR data made available in Italy from the Extreme Energy Events project (http://eee.centrofermi.it/monitor). Air mass back-trajectories were used to confirm the observed aerosol types and support the correlation study. Our study showed promising results in understanding the relationship between cosmic ray and aerosol properties.

Keywords: Cosmic Ray, Aerosol, Lidar, Sun Photometer, Back-trajectory

How to cite: Karimian Sarakhs, F., Madonna, F., Rosoldi, M., and De Pasquale, S.: Relationship between the time series of cosmic ray data and aerosol optical properties: (Case study: southern Italy, 2016-2020), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8872, https://doi.org/10.5194/egusphere-egu22-8872, 2022.

Cosmic ray neutron sensing has been shown to be a powerful method for continuously monitoring soil moisture over large areas. This technique relies on the detection of albedo cosmic ray neutrons coming from from the soil to infer the local hydrogen content. Cosmic ray neutron sensing is well-suited for hydrological monitoring in the field sizes typically seen on smallholder farms. The ongoing development of new lower-cost neutron detector instrumentation and processing tools will help to further support the adoption of this novel technique within the agricultural industry.

In this presentation I will discuss recent efforts at Durham University (UK) to develop low-cost cosmic ray neutron detectors to support soil moisture monitoring in the agriculture sector. These systems rely on lithium and boron-based scintillator foils for thermal neutron detection. Recent pilot studies in collaboration with the COSMOS-UK network have shown that the detected neutron rate in these sensors correlates well with results obtained from traditional gaseous systems. Work is now underway to improve the robustness of these scintillator systems for use in agricultural and civil engineering applications. 

In addition, I will present a new international research network, COSMIC-SWAMP, which is looking at the integration of cosmic ray neutron sensors with managed irrigation sites in Brazil. By combining low-cost neutron probes with a smart water management platform (SWAMP), this research network is looking at using cosmic ray neutrons to perform data-driven irrigation control over large areas. The instrumentation being considered for COSMIC-SWAMP will be presented before discussing the future plans for the network.

How to cite: Stowell, P. and the COSMIC-SWAMP and STFC Food Network+ Collaborations: Smart Scintillating Neutron Detectors for Soil Moisture Monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9264, https://doi.org/10.5194/egusphere-egu22-9264, 2022.

The geomagnetic field prevents energetic particles, such as galactic cosmic rays, from directly interacting with the Earth's atmosphere. The geomagnetic field is not static but constantly changing, and over the last 100,000 years several geomagnetic excursions occurred. During geomagnetic field excursions, the field strength is significantly decreased and the field morphology is controlled by non-dipole components, and more cosmic ray particles can access the Earth's atmosphere. Paleomagnetic field models provide a global view of the long-term geomagnetic field evolution, however, with individual spatial and temporal resolution. Here, we reconstruct the geomagnetic shielding effect over the last 100,000 years by calculating the geomagnetic field cutoff rigidity using four global paleomagnetic field models, i.e., GGF100k, GGFSS70, LSMOD.2, and CALS10k.2. We find that the non-dipole components of the geomagnetic field are not negligible for estimating the long-term geomagnetic shielding effect, in particular during excursions. Our results indicate that cosmic ray flux, impact area, and cosmic ray radiation intensity increase strongly during the excursions. Our results provide the possibility to accurately estimate the cosmogenic isotope production rate and cosmic radiation dose rate covering the last 100,000 years.

How to cite: Korte, M., Gao, J., and Panovska, S.: Geomagnetic field shielding over the past 100 000 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9438, https://doi.org/10.5194/egusphere-egu22-9438, 2022.

The generation of cosmogenic tritium (³H) through spallation of ¹⁴N in the upper atmosphere and a its decay (half-life of 12.32 y) are the two main processes resulting in the global steady-state inventory of tritium in the hydrosphere of approximately 2.95 kg. Various mechanisms of scavenging of stratospheric ³H into the troposphere, such as stratosphere-troposphere transports (STTs) during the so-called “spring leak”, or the tropospheric distribution by means of the Brewer-Dobson circulation, have been described to explain the observed spatial and seasonal distribution of present-day tritium levels in global precipitation. Following thermonuclear weapons testing prior to the Preliminary Test Ban Treaty in 1963, the natural ³H input signal was overlaid by the so-called “bomb peak”. This characteristic tritium pulse has been used for decades in nuclear and hydrological sciences, with ³H values in Vienna, the reference northern hemisphere station of the IAEA-WMO Global Network of Isotopes in Precipitation (GNIP), peaking in 1963 at approximately 400 Bq L^-1. Since the year 2000, this ³H pulse has dissipated in the northern hemisphere, and ³H levels at the Vienna monitoring site have reached their natural background value of ca. 1.2 Bq L^-1.

The present-day steady state of natural ³H levels in precipitation allow to research their inter-annual variability as driven by cosmogenic input, with particular emphasis on neutron flux intensity governed by the 11-year sunspot cycles. With almost two full solar cycle’s worth of observed ³H data in Vienna’s precipitation and other GNIP stations in the northern hemisphere, we discuss the impact of the neutron flux (as exemplified by the Oulu Neutron Monitor) in modulating the inter-annual variability. Our findings showed that while 52% of the interannual variability was explained by changes in the cosmogenic flux, an additional 31% of the variability resulted from the seasonal distribution of the amount of precipitation, a finding prominent in the previous solar cycle valley, particularly in the year 2015, that coincided with abnormally high winter precipitation.

While the regular oscillations of the neutron flux seem to constitute the main driver of the observed interannual changes of ³H contents in precipitation, atmospheric circulation processes were of varying importance in 15 GNIP stations. In spite of the relative data paucity (i.e. absence of sufficiently long records at even spatial distribution), we hypothesize that changes in precipitation seasonality, due to climate change impacts on global or regional atmospheric circulation patterns, may drive fluctuations in the natural steady-stage ³H levels in precipitation used to investigate atmospheric and hydrological processes. Hence, we stress the importance of spatially and temporally adequate observational baselines on a global level.

How to cite: Terzer-Wassmuth, S., Araguas-Araguas, L. J., Copia, L., and Miller, J. A.: Space or climate? Disentangling cosmogenic and climatic drivers of present-day tritium (3H) in global precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11230, https://doi.org/10.5194/egusphere-egu22-11230, 2022.

Cosmic ray neutron sensing (CRNS) has become an established method for deriving the soil water content (SWC), based on the inverse relationship of neutron counting and the SWC of the surrounding area. The provided footprint, lateral up to 200m and vertical of several decimeter, qualifies CRNS to bridge the information gap between classical hydrogeophysical approaches and remote sensing. While stationary CRNS offers continuous long-term SWC measurements at high temporal resolution, the covered area remains fixed and predefined. Car-borne CRNS roving on the other hand, allows to expand the mapped area. However, the method requires active operation and is limited to snap shot information only. As an alternative, the operation of a permanent mobile CRNS platform on trains promises to combine the advantages from stationary and car-borne CRNS measurements, as recently suggested by Schrön et al. (2021), while also its technical implementation, data processing and interpretation raises new challenges and complexity.

In this study we introduce a fully automatic CRNS railway system, installed in a conventional locomotive of a freight train, as first and novel of its kind. Results of the first phase of operation will be presented. The measurements along an experimental rail track were supported by local SWC measurements, gravimetric and dielectric records (Mobile Wireless Ad-hoc Sensor Network), at three areas along the railway, and by a newly installed weather station. Additionally, car-borne CRNS data were recorded on two days close to the railway track.

Preliminary results of data collected between September and December 2021 showed very stable spatial pattern in relation to the segments crossed by the train, which have been confirmed by the car-borne dataset. Temporal variations within hours were also evident as direct or indirect response to local rain and snow events.  Based on the first results, we are confident, that rail-based CRNS offers the chance to play a prominent role in addressing soil hydrology at landscape scale in the future.

Schrön, M., Oswald, S. E., Zacharias, S., Kasner, M., Dietrich, P., & Attinger, S. (2021). Neutrons on rails: Transregional monitoring of soil moisture and snow water equivalent. Geophysical Research Letters, 48, e2021GL093924

How to cite: Altdorff, D., Oswald, S., Zacharias, S., Zengerle, C., Mollenhauer, H., Dietrich, P., Attinger, S., and Schrön, M.: Rail-based cosmic ray neutron sensing (CRNS): pushing the boundaries towards expanding footprints and temporal resolutions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12334, https://doi.org/10.5194/egusphere-egu22-12334, 2022.

Cosmogenic isotopes are mostly produced in the stratosphere and troposphere, and the corresponding fractions depend on solar activity and tropopause altitude. Solar-cycle variability of cosmogenic isotope production is the strongest at high latitudes due to the lack of geomagnetic shielding. However, the exact zonal distribution of the production in troposphere and stratosphere regions, that is needed for the precise modelling of their transport and deposition, is not clear. In this work, we provide numerical estimates of cosmogenic isotopes production in the atmosphere for different conditions. Using the SOCOL-AER2-BE Chemical Climatic model (CCM), we present simulations of the production of cosmogenic isotopes ($^{14}$C, $^{36}$Cl, $^{10}$Be, and $^{7}$Be) and provide zonal distributions (tropical, subtropical, and polar regions) in the stratosphere and troposphere. The model is driven by four solar activity scenarios: 1) solar minimum year with solar modulation function - phi = 400 MeV and 2) solar maxima year with phi = 1100MeV. In these cases, the production is modulated by Galactic Cosmic Rays (GCR). Two other scenarios are 3) ground-level enhancement (GLE) event number 5 with hard spectrum on February 23, 1956 and 4) GLE event number 24 with soft spectrum on August 04, 1972. The production rates were calculated using a combination of the SOCOL and CRAC models.

How to cite: Golubenko, K.: Zonal distribution of cosmogenic isotopes in stratosphere and troposphere via CCM SOCOL, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12618, https://doi.org/10.5194/egusphere-egu22-12618, 2022.

Cosmic-Ray Neutron Sensing (CRNS) is an established measurement technique for water content in soils and snow. The high integration depth and the large measurement footprint is an important advantage compared to conventional point-scale sensors. However, the radial-symmetrical footprint definition based on the 86% quantile of detected neutrons is often not helpful to explain the influence of certain areas in complex fields. Many natural sites are highly heterogeneous and thus knowledge of the contribution of distant areas to the measurement signal would be very useful, e.g. to support calibration sampling, sensor location design, data interpretation, and uncertainty assessment. Here, CRNS calibration and validation remains a challenge, since the influence of the different fields and structures to the signal is usually not known.

In this presentation, we proposes a generalized analytical procedure to estimate the contribution of patches or fields in the footprint of a cosmic-ray neutron detector to its signal using the radial intensity functions. The proposed method could greatly support calibration sampling, sensor location design, and uncertainty assessment, e.g. in complex or vegetated terrain, without the need of computationally expensive neutron modeling. Furthermore, a new concept for a more practical definition of the sensor footprint is proposed, which represents the maximal distance to a field such that its soil moisture change is still sensible in terms of measurement precision. 

How to cite: Schrön, M., Köhli, M., and Zacharias, S.: Signal contribution of remote areas to cosmic-ray neutron sensors based on distance and sensitivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12812, https://doi.org/10.5194/egusphere-egu22-12812, 2022.

We present the study of the propagation of energetic particles through a non-parkerian, data-driven solar wind solution for the event of 15 March 2013. In the study, we employed the recently coupled models EUHFORIA (EUropean Heliospheric FORecasting Information Asset) and PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration). 

An Earth-directed, asymmetric, full halo CME erupted from the Sun on March 15, 2013. An associated GOES M1.1 X-ray flare was observed originating from the active region 11692, reaching its peak intensity at 06:58 UT. Shortly after, at 7:12 UT, a CME was observed by coronagraphs at both STEREO and SOHO/LASCO spacecraft. During March 16, the particle counts at L1 were enhanced, and measurements show different profiles for different energy ranges, with a distinct two-step increase in the lower energy channels lasting for several days. 

The 3D MHD heliospheric solar wind and CME evolution model EUHFORIA was used to simulate this event, with special emphasis on fitting the modeled and observed CME characteristics and signatures at Earth. The energetic particles (SEPs) were simulated with the newly developed solar energetic particle transport model PARADISE. The EUHFORIA simulation results were employed as the time-dependent ambient plasma characteristics. Particle populations with different characteristics were explored with the aim to accurately describe and reproduce the in situ measured particles. Moving sources of particles were incorporated in order to model the CME shock-generated part of the population. The first results of this complex simulation will be shown in this presentation.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Niemela, A., Wijsen, N., Aran, A., Rodriguez, L., Magdalenic, J., and Poedts, S.: Analysis of the CME and associated gradual SEP event of March 2013, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-959, https://doi.org/10.5194/egusphere-egu22-959, 2022.

Medium energy electron (MEE) (>30 keV) precipitation into the Earth's atmosphere is acknowledged as a relevant part of solar forcing as collisions between electrons and atmospheric gasses initiate several chemical reactions which can reduce ozone concentration. Ozone is critically important in the middle atmosphere energy budget as changes in ozone concentration impact temperature and winds. There is an ongoing debate to which extent the existing geomagnetic parameterizations represent a realistic precipitating flux level, especially when considering the high energy tail of MEE (>300 keV). An improved quantification might be achieved by a better understanding of the driving processes of MEE acceleration and precipitation, alongside optimized data handling. In this study, the bounce loss cone fluxes are inferred from MEE precipitation measurements by the Medium Energy Proton and Electron Detector (MEPED) on board the Polar Orbiting Environmental Satellite (POES) and the Meteorological Operational Satellite Program of Europe (METOP) at tens of keV to a couple hundred keV. It investigates MEE precipitation in contexts of different solar wind structures: corotating interaction regions (CIRs) associated with high-speed solar wind streams (HSSs), and coronal mass ejections (CMEs), during an eleven-year period from 2004 – 2014. The objective of this study is to explore general features of the MEE precipitating spectrum in the context of its solar wind driver: the intensity of MEE alongside the intensity and delayed response of its high energy tail.

How to cite: Salice, J., Tyssøy, H. N., Smith-Johnsen, C., and Babu, E. M.: Solar Wind Structures and their Effects on the High-Energy Tail of the Precipitating Energetic Electron Spectrum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2745, https://doi.org/10.5194/egusphere-egu22-2745, 2022.

Modeling of time profiles of solar energetic particle (SEP) observations typically considers transport along a large-scale magnetic field with a fixed path length from the source to the observer.  Chhiber et al. (2021) pointed out that the path length along a turbulent magnetic field line is longer than that along the large scale field, and that the path along the particle gyro-orbit can be substantially longer again; they also considered the global variation in these quantities.  Here we point out that variability in the turbulent field line path length can affect the fits to SEP data and the inferred mean free path and injection profile.  To explore such variability, we perform Monte Carlo simulations in representations of homogeneous 2D MHD + slab turbulence in spherical geometry and trace trajectories of field lines, particle guiding centers, and full particle orbits, considering ion injection from a narrow or wide angular region near the Sun, corresponding to an impulsive or gradual solar event, respectively. We analyze our simulation results in terms of path length statistics within and among square-degree pixels in heliolatitude and heliolongitude at 0.35 and 1 AU from the Sun.  For a given representation of turbulence, there are systematic effects on the path lengths vs. heliolatitude and heliolongitude.  Field line path lengths relate to the fluctuation amplitudes experienced by the field lines, which in turn partly relate to the local topology of 2D turbulence.  Particles from an impulsive event that arrive at a distant angular separation (up to ~25 degrees from the mean field connection) generally have longer path lengths, not because of the angular distance per se but because of strong magnetic fluctuations experienced to drive the guiding field lines to such angular distances and because of the associated scattering of the particles.  We describe the effects of such path length variations on observed time profiles of solar energetic particles, both in terms of path length variability at specific locations and motion of the observer with respect to turbulence topology during the course of the observations.  This research was partially supported by Thailand Science Research and Innovation grant RTA6280002 and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165).  Additional support is acknowledged from the NASA LWS program (NNX17AB79G) and HSR program (80NSSC18K1210 & 80NSSC18K1648).

How to cite: Sonsrettee, W., Chuychai, P., Seripienlert, A., Tooprakai, P., Sáiz, A., Ruffolo, D., Matthaeus, W. H., and Chhiber, R.: Magnetic Field Line Path Length Variations and Effects on Solar Energetic Particle Transport, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3394, https://doi.org/10.5194/egusphere-egu22-3394, 2022.

Simultaneous observations of large Solar Energetic Particle (SEP) events by multiple spacecraft located near 1 AU during solar cycle 24  have shown an east-west asymmetry of the peak intensities of SEPs with respect to the source flare locations. Using the 2D improved Particle Acceleration and Transport in the Heliosphere (iPATH) model, we consider multiple cases with different solar wind speeds and eruption speeds of the Coronal Mass Ejections (CMEs) and fit the longitudinal distributions of time-averaged fluence by Gaussian functions in 8-, 24- and 48-hour respectively. The simulation results are compared with a statistical study of 28 3-spacecraft (SC) events. The east-west asymmetry shows a clear time-dependent and energy-dependent evolution. We suggest that the east-west asymmetry of SEP fluence (and peak intensity) is a consequence of the combined effect of an extended shock acceleration process and the evolution of magnetic field connection to the shock front. Our simulations show that the solar wind speed and the eruption speed of CMEs are essential factors for the east-west fluence asymmetry. 

How to cite: Ding, Z. and Li, G.: Modelling the east-west asymmetry of energetic particle fluence in large solar energetic particle  events using the iPATH model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3603, https://doi.org/10.5194/egusphere-egu22-3603, 2022.

In this work, we model the energetic storm particle (ESP) event of 14 July 2012 using the energetic particle acceleration and transport model named PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration), together with the solar wind and coronal mass ejection (CME) model named EUHFORIA (EUropean Heliospheric FORcasting Information Asset).  The CME generating the ESP event is simulated by using the spheromak model of EUHFORIA, which approximates the CME’s magnetic field as a linear force-free spheroidal magnetic field. The energetic particles are modelled by injecting a seed population of 50 KeV protons continiously at the CME-driven shock wave. The simulation results illustrate both the capabilities and limitations of the utilised models.  

We find that for energies below 1 MeV, the simulation results agree well with the upstream and downstream components of the ESP event observed by the Advanced Composition Explorer (ACE).  This suggests that these low-energy protons are mainly the result of interplanetary particle acceleration. In the downstream region, the sharp drop in the energetic particle intensities is reproduced at the entry into the following magnetic cloud, illustrating the importance of a magnetised CME model.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Wijsen, N., Aran, A., Scolini, C., Lario, D., Afanasiev, A., Vainio, R., Pomoell, J., Sanahuja, B., and Poedts, S.: Observation-based modelling of the energetic storm particle event of 14 July 2012, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5899, https://doi.org/10.5194/egusphere-egu22-5899, 2022.

On October/November 2021 the Heavy Ion Sensor onboard Solar Orbiter observed data connected to three interplanetary shock events: Oct 30, Nov 3 and Nov 27. During all three events, the flux of suprathermal particles, defined as those having an energy larger than twice the energy of the solar wind component, showed remarkable intensification. We discuss those changes and specifically how particles of different mass/charge and energy/charge distribution before the shock are affected differently by the interaction with the shock front itself. From these three expampes, it appears that intensifications are stronger for species already having a seed population in the suprathermal regime.

How to cite: Livi, S., Owen, C., Louarn, P., Fedorov, A., Alterman, B., Lepri, S., Raines, J., Galvin, A., Kistler, L., Allegrini, F., Ogasawara, K., Wurz, P., Bruno, R., D'Amicis, R., and Collier, M.: Preferential Acceleration of Suprathermal Particles at Shocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5984, https://doi.org/10.5194/egusphere-egu22-5984, 2022.

Medium energy electron (MEE) (30-1000 keV) precipitation enhances the production of nitric (NO_x) and hydrogen oxides (HO_x) throughout the mesosphere, which can destroy ozone (O₃) in catalytic reactions. The dynamical effect of the direct mesospheric O₃ reduction has long been an outstanding question, partly due to the concurrent feedback from the stratospheric O₃  reduction. To overcome this challenge, the Whole Atmosphere Community Climate Model (WACCM) version 6 is applied in the specified dynamics mode for the year 2010, with and without MEE ionization rates. The results demonstrate that MEE ionization rates can modulate temperature, zonal wind and the residual circulation affecting NO_x transport. The required fluxes of MEE to impose dynamical changes depend on the dynamical preconditions. During the Northern Hemispheric winter, even weak ionization rates can modulate the mesospheric signal of a sudden stratospheric warming event. The result is a game changer for the understanding of the MEE direct effect.

How to cite: Nesse Tyssøy, H., Zúñiga, H. D. L., Smith-Johnsens, C., and Maliniemi, V.: The medium energy electron direct effect on mesospheric dynamics during a sudden stratospheric warming event in 2010, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7106, https://doi.org/10.5194/egusphere-egu22-7106, 2022.

The propagation of Solar Energetic Particles (SEPs) has been described traditionally by means of a spatially 1D focussed transport approach. However in recent years a number of physical mechanisms that give rise to motion across the mean magnetic field have been studied. These include perpendicular transport associated with turbulence, guiding centre drifts and drift along the heliospheric current sheet. In this presentation such mechanisms will be reviewed and emphasis will be placed on how assumptions and scenarios based on a 1D approach need to be modified when looking at SEP propagation from a 3D perspective. Observables such as time intensity profiles and anisotropies obtained from 3D models will be discussed and compared with observations.

How to cite: Dalla, S.: Role of 3D propagation in shaping Solar Energetic Particle observables, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7635, https://doi.org/10.5194/egusphere-egu22-7635, 2022.

Observations of Energetic Electron Substorm Injection Signatures by Cluster and BepiColumbo During an Earth Flyby

We present an analysis of the energetic electron signatures observed by BepiColumbo and Cluster during the Bepi flyby of Earth on 10 April 2020, as well as other spacecraft. After closest approach, the SIXS instrument on Bepi observed two separate substorm injection fronts, while Cluster RAPID/IES also observed a sequence of energetic electron signatures. Bepi and Cluster were in a particularly favourable configuration during this event, with Bepi moving rapidly radially outward near the nightside equatorial plane while the four Cluster spacecraft cut the same region in a north/south direction in a string of pearls configuration. The coincidence of this favourable geometry with the substorm activity is highly fortuitous and appears to show a complicated sequence of spatially and temporally separated injections and drift echoes.

How to cite: Grande, M., Sanches-Cano, B., Nakamura, R., Vainio, R., Miyoshi, Y., Dandouras, I., Johnson, R., Oleynik, P., Nakamura, S., Perry, C., Johnson, P., Huovelin, J., Maguire, S., and Heyner, D.: Observations of Energetic Electron Substorm Injection Signatures by Cluster and BepiColumbo During an Earth Flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8067, https://doi.org/10.5194/egusphere-egu22-8067, 2022.

Energetic particle populations in the solar corona and in the heliosphere appear to have different characteristics even when produced in the same solar flare. It is not clear what causes this difference: properties of the acceleration region, the large-scale magnetic field configuration in the flare, or particle transport effects, such as scattering. We use a combination of non-linear force-free magnetohydrostatic simulations, magnetohydrodynamic and test-particle modelling to investigate magnetic reconnection, particle acceleration and transport in two solar flares events: an  M-class flare on  June 19th, 2013, and an X-class flare on September 6th, 2011. We show that, although in both events particles are energised at the same locations, the magnetic field structure around the acceleration region results in different characteristics between particle populations precipitating towards the photosphere and those ejected towards the upper corona and the heliosphere. We expect this effect to be ubiquitous when particles are accelerated close to the boundary between open and colsed magnetic fields and, therefore, may be key to solar flares with  substantial particle emission into the heliosphere. Furthermore, this analysis elucidates the mechanisms by which escaping particle populations can be created in flares.

How to cite: Browning, P. and Gordovskyy, M.: Energetic particle emission in two solar flares with open magnetic field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8518, https://doi.org/10.5194/egusphere-egu22-8518, 2022.

We report on the annual variation of quiet-time suprathermal ion composition and spectral properties for C-Fe using Advanced Composition Explorer (ACE)/Ultra-Low Energy Isotope Spectrometer (ULEIS) data over the energy range 0.3 MeV/nuc to 1.28 MeV/nuc from 1998 through 2019. We show that (1) the number of quiet-time hours strongly anti-correlates with the annual Sunspot Number (SSN) at the -0.95 level; (2) a clear ordering of the cross correlation between abundance (normalized to O) and SSN as a function of solar wind mass-per-charge M/Q; (3) the slope of X/O abundance as a function of Fe/C decreases with increasing M/Q; and (4) annual spectral indices γ = 2.5 independent of solar activity and M/Q. We also discuss the trend of annual spectral indices with respect to Oxygen’s spectral index as a function of solar cycle and M/Q. Using our quiet time selection methods, we show that our results are robust against our quiet time selection criterion.

How to cite: Alterman, B. L., Desai, M. I., Dayeh, M., Mason, G. M., and Ho, G.: Quiet Time Suprathermals Across Solar Cycle 23 & 24: Abundances and Spectral Indices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8953, https://doi.org/10.5194/egusphere-egu22-8953, 2022.

Solar electrons beams are accelerated in the corona, and can travel out into the solar wind and beyond. These beams of non-thermal electrons evolve as a function of distance from the Sun, interacting with the background plasma and growing Langmuir waves as they propagate. Subsequent radio emission is also seen in the form of type III bursts. Around 1 AU, we detect in-situ electrons up to 10-20 keV together with local Langmuir waves. However, previous studies suggest that higher energy electrons interact with Langmuir waves close to the Sun and so these electrons would not propagate scatter-free. Through beam-plasma structure simulations we study the interactions between these electron beams and the background plasma of the solar corona and the solar wind at different distances from the Sun, up to 130 solar radii. This allows us to determine what is the maximum electron velocity responsible for Langmuir wave production and growth, and consequently which electron energies are affected by wave-particle interactions as a function of distance from the Sun. We also vary the spectral index of the electron velocity distribution α and the electron beam density n_beam to identify what role they play in determining the relevant electron velocities at which wave-particle interactions occur. Understanding the mechanisms driving the change in the maximum electron velocity will permit more accurate predictions in electron onset as well as arrival times, relevant for space weather applications and the understanding of the subsequent emissions at radio and X-ray wavelength. Moreover, our radial predictions can be tested against in-situ electron and plasma measurements from the instruments on-board the Solar Orbiter and Parker Solar Probe spacecrafts.

How to cite: Lorfing, C. and Reid, H.: Evolution of solar accelerated electron beams as a function of distance from the Sun, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9873, https://doi.org/10.5194/egusphere-egu22-9873, 2022.

The energy released during a solar flare is efficiently transferred to energetic non-thermal particles, though the exact plasma properties of the acceleration region and the importance of individual acceleration mechanisms is not fully understood. Non-thermal acceleration of electrons in the solar atmosphere is observed from two main sources: in-situ detection of solar energetic electrons (SEEs) in interplanetary space and remote observation of high-energy emission (e.g. X-rays, radio) at the Sun itself. While these two populations are widely studied individually, a common flare-associated acceleration region has not been established. If such a region were to exist, its properties would also need to be determined based on both remote and in-situ observations.

We present preliminary results of a parameter search of the plasma properties and possible acceleration processes in a common solar acceleration region and compare the results of precipitating and escaping electrons. The number density, plasma temperature and the size of the acceleration region itself, as well as properties such as turbulence leading to acceleration, are variable parameters in a transport model code including collisional and non-collisional processes, simulating electrons in the Solar atmosphere and heliosphere. The results of these simulations produce electron time profiles, pitch-angle distributions and energy spectra at the Sun (corona and chromosphere), at 1 AU and other heliospheric locations with which to compare directly with observational data from modern instruments including those mounted on Solar Orbiter.  

The ultimate goal of this study is to model the precipitating and escaping electron populations and compare the resultant properties with observations of solar events where both remote and in-situ observations are available. With this forward modelling approach, we aim to constrain the plasma properties and transport effects present in the solar atmosphere and heliosphere.

How to cite: Pallister, R. and Jeffrey, N.: Simultaneous modelling of flare-accelerated electrons at the Sun and in the heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10114, https://doi.org/10.5194/egusphere-egu22-10114, 2022.

The particle flux in the near-Earth environment can increase by orders of magnitude during geomagnetically active periods. This leads to intensification of particle precipitation into Earth’s atmosphere. The process potentially further affects atmospheric chemistry and temperature.

In this research, we concentrate on ring current electrons and investigate precipitation mechanisms on a short time scale using a numerical model based on the Fokker-Planck equation. We focus on understanding which kind of geomagnetic storm leads to stronger electron precipitation. For that, we considered two storms, corotating interaction region (CIR) and coronal mass ejection (CME) driven, and quantified impact on ring current. We validated results using observations made by POES satellite mission, low Earth orbiting meteorological satellites, and Van Allen Probes, and produced a dataset of precipitated fluxes that covers energy range from 1 keV to 1 MeV.

How to cite: Grishina, A., Shprits, Y., Wutzig, M., Allison, H., Aseev, N., Wang, D., and Szabo-Roberts, M.: Ring Current Electron Precipitation During Storm Events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11023, https://doi.org/10.5194/egusphere-egu22-11023, 2022.

One source of solar energetic particle (SEP) events are shocks that are driven by fast Coronal Mass Ejections (CMEs). These can accelerate SEPs up to relativistic energies and are attributed to the largest SEP events. Even though the exact role of shocks for accelerating SEP electrons is still under debate, new studies suggest that CME-driven shocks can efficiently accelerate electrons to MeV energies in the vicinity of the Sun.

In this ongoing study, we present STEREO spacecraft observations of potential electron Energetic Storm Particle (ESP) events, characterized by intensity time series that peak at the time of the associated CME-driven shock crossing. We study near-relativistic and relativistic electrons during strong IP shocks between 2007 and 2018, to answer if the shock can actually keep accelerating electrons up to 1 AU distance. We use both, the Solar Electron and Proton Telescope (SEPT) and the High Energy Telescope (HET).

We focus especially on the MeV electron measurements and study if these are real or if the increases during the shock crossing are caused by strong proton contamination in the instrument. Therefore, we investigate the time profiles of the SEP events from the beginning until the crossing of the CME-associated shock and perform a correlation analysis of electron and proton intensities. We also investigate the in-situ plasma and magnetic field measurements at the spacecraft and analyze the energy spectrum of upstream regions of the shocks to shed light on the shock acceleration mechanism.

How to cite: Talebpour Sheshvan, N., Dresing, N., Vainio, R., and Afanasiev, A.: The Role of Interplanetary Shocks for Accelerating MeV Electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11283, https://doi.org/10.5194/egusphere-egu22-11283, 2022.

This report presents the results of observations of Solar Particle Events (SPE) in July-October 2021 that have been simultaneously detected by the MGNS (Mercury Gamma-ray and Neutron Spectrometer) instrument on board the MPO spacecraft of the BepiColombo mission which is currently on a cruise phase to Mercury, as well as by science instruments that are operated in near-Mars orbit: HEND (High Energy Neutron Detector) instrument onboard Mars Odyssey mission, FREND (Fine Resolution Epithermal Neutron Detector) instrument and Liulin-MO dosimeter onboard ExoMars TGO (Trace Gas Orbiter) mission. This location of the spacecrafts, allowed for stereoscopic observation of SPEs, in addition during the period July-October 2021 Mars is on the opposite side of the Sun from Earth, when it is difficult to observe these SPEs by instruments on a near-Earth group of spacecrafts for Solar monitoring. The report will present an analysis of the energy spectra deposition and analysis of time profiles. In particular it shows the Forbush decrease of GCR in effect of the arrival of the dense solar plasma to the SPE observation locations. The MGNS, HEND and FREND instrument developed and manufactured at the Space Research Institute of the Russian Academy of Sciences and are a Russian-made and Russian-funded contribution by the Russian Federal Space Agency (ROSCOSMOS) to the BepiColombo, Mars Odyssey and ExoMars TGO missions, respectively. Liulin-MO has been developed in Space Research and Technology Institute at the Bulgarian Academy of Sciences with participation of Institute of Biomedical Problems of the Russian Academy of Sciences (Moscow) and Institute for Space Research (Moscow).

Acknowledgements

The work in Bulgaria is supported by grant KP-06-Russia 24 for bilateral projects of the National Science Fund of Bulgaria and Russian Foundation for Basic Research.

How to cite: Kozyrev, A., Litvak, M., Malakhov, A., Mitrofanov, I., Semkova, J., Koleva, R., Benghin, V., Krastev, K., Matviichuk, Y., Tomov, B., Maltchev, S., Bankov, N., Shurshakov, V., and Drobyshev, S.: Observation of solar particle events from MGNS experiment onboard BepiColombo mission, HEND experiment onboard Mars Odyssey mission, and also FREND and Liulin-MO experiments onboard TGO mission during July-October 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11521, https://doi.org/10.5194/egusphere-egu22-11521, 2022.

Energetic particle precipitation (EPP) into the atmosphere, lead to chemical reactions producing NOx gases. Auroral electrons deposit their energy at altitudes throughout the upper mesosphere and lower thermosphere. During the winter the EPP-produced NOx gases can survive for months and be transported down to the stratosphere, where it can destroy ozone through catalytic reactions. Studies comparing the NO density estimated by chemistry climate models and observations suggest that the estimation of NO-production by auroral forcing is overestimated during quiet times and underestimated during active time. This study provides an intercomparison of different auroral forcing estimates. We compare fluxes from the Total energy detector (TED) onboard the NOAA Polar Orbiting Environmental Satellites (POES) and Meteorological Operational satellite (MetOp), sensor for precipitating particles (SSJ) from Defense Meteorological spacecraft Program (DMSP), alongside a Kp-driven auroral model. The data over a full year was sorted by the daily Kp and evaluated as function of geomagnetic latitude and magnetic local time. Discrepancies are evaluated in respect to geographical bias, as well as geometric factors of the satellites. Furthermore, the observations are compared to the Kp-driven auroral model.

How to cite: Eide, H. D., Tyssøy, H. N., Tesema, F., and Babu, E. M.: What is the flux of low energy electron precipitation in the lower thermosphere?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11792, https://doi.org/10.5194/egusphere-egu22-11792, 2022.

Fluxes of solar energetic particles (SEPs) are associated with solar flares and coronal/interplanetary shock waves. In the case of shocks, particles are thought to get accelerated to high energies via the diffusive shock acceleration mechanism. In order to be efficient, this mechanism requires an enhanced level of magnetic turbulence in the vicinity of the shock front, in particular, in the so-called foreshock region upstream of the shock. This turbulence enhancement can be produced self-consistently, i.e., by the accelerated particles themselves via streaming instability. This idea underlies the SOLar Particle Acceleration in Coronal Shocks (SOLPACS) Monte-Carlo simulation code, which we developed earlier to simulate acceleration of protons in coronal shocks. In the present work, we apply SOLPACS to model an energetic storm particle (ESP) event measured by the STEREO A spacecraft on November 10, 2012. All but one main SOLPACS input parameters are fixed by the in-situ plasma measurements from the spacecraft. Comparison of a simulated proton energy spectrum at the shock with the observed one then allows us to fix the last simulation input parameter related to efficiency of particle injection to the acceleration process. Subsequent comparison of simulated proton time-intensity profiles in a number of energy channels with the observed ones shows a very good correspondence throughout the upstream region. Our results give support for the quasi-linear formulation of the foreshock. This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Afanasiev, A., Talebpour Sheshvan, N., Vainio, R., Dresing, N., Trotta, D., Hietala, H., and Nyberg, S.: Self-consistent Monte-Carlo modeling of the November 10, 2012 energetic storm particle event, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11915, https://doi.org/10.5194/egusphere-egu22-11915, 2022.

Investigating the motion of charged particles in time- and space-dependent electromagnetic fields is central to many areas of space and astrophysical plasmas. Here we present results of studying the energy changes of particle orbits that are trapped in inhomogeneous magnetic fields with rapidly shortening field lines. These so-called collapsing magnetic trap (CMT) models can be useful for explaining the acceleration of particles below the reconnection region in a solar flare. For both 2D and 3D CMT models (e.g. Giuliani et al. 2005; Grady & Neukirch, 2009), betatron acceleration was considered to be the dominant energisation mechanism. We present new results that have been obtained using an improved version of the 3D CMT model by Grady and Neukirch (2009). Our investigations show that a sizeable portion of particle orbits can gain a significant amount of energy that is not explained by the betatron effect. The other mechanism at play appears to be Fermi acceleration at loop tops, where the particle passes through the region of field that is collapsing the most rapidly. 

We show that the particles that experience this effect the most have initial positions that are related to specific regions of the magnetic field model and it is these particle orbits whose energy gains are not adequately explained by betatron acceleration alone. In fact, some particle orbits seem to gain energy almost entirely as a result of this Fermi acceleration. One can also show that for suitable initial conditions the same effect can be seen in the 2D CMT model given by Giuliani et al. (2005). This updated understanding of the systems at play for particle acceleration in a CMT can, for example, inform any changes made to future CMT models by accounting for the large number of particles that see energy gains due to Fermi acceleration. 

Giuliani, P. et al., ApJ 635, 636

Grady, K. & Neukirch, T., A&A 508, 1461 

How to cite: Mowbray, K. and Neukirch, T.: Particle Energisation in Collapsing Magnetic Traps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11965, https://doi.org/10.5194/egusphere-egu22-11965, 2022.

We are examining a new kind of hybrid method for finding SEP (Solar Energetic Particle) event onset times and assessing their uncertainties. Determining these onset times accurately is important because they are needed to relate the in-situ particle measurements to remote-sensing observations of the associated activity phenomena at the Sun. Only by this, can one identify the actual region and acceleration processes that generated the event. Different methods have been used to determine this onset time; however, the most common ones do not provide reasonable uncertainties so far. The method presented here employs a combination of a statistical quality control scheme, the Poisson-CUSUM (cumulative sum) method, and statistical bootstrapping for calculating a distribution of the necessary parameters for the Poisson-CUSUM method.

The CUSUM method is a statistical quality control scheme, used also in many industries, that is designed to give an early warning when the inspected process or variable changes (Page, 1954). Poisson-CUSUM refers to a specific cumulative sum method that assumes that the monitored variable has a Poisson distribution. 

By randomly choosing samples from the particle flux preceding the event, we acquire a distribution of different values for the estimated mean flux and for the standard deviation of the background measurements. These two distributions produce a set of possible onset times via the Poisson-CUSUM method, allowing us to evaluate the uncertainty of an onset time by the precision of our set of candidate onset times, and also to identify the most likely onset time. In addition, we apply the new method to energetic particle observations of the Solar Orbiter spacecraft that come with high energy and time resolution, and perform velocity dispersion analyses. 

• S. PAGE, CONTINUOUS INSPECTION SCHEMES, Biometrika, Volume 41, Issue 1-2, June 1954, Pages 100–115, https://doi.org/10.1093/biomet/41.1-2.100

How to cite: Palmroos, C., Dresing, N., Gieseler, J., Vainio, R., and Asvestari, E.: Determining SEP Event Onset Times and Evaluating Their Uncertainty Using a Poisson CUSUM-Bootstrap Hybrid Method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12111, https://doi.org/10.5194/egusphere-egu22-12111, 2022.

The Earth is continuously exposed to galactic cosmic rays. The flux of these particles is altered by the magnetized solar wind in the heliosphere and the Earth's magnetic field. If cosmic rays hit the atmosphere they can form secondary particles. The total flux measured within the atmosphere depends on the atmospheric density above the observer. Therefore, the ability of a particle to approach an aircraft depends on its energy, the altitude and position of the aircraft. The latter is described by the so-called cut-off rigidity.
The radiation detector of the detector system NAVIDOS (NAVIgation DOSimetry) is the DOSimetry Telescope (DOSTEL) measuring the count and dose rates in two semiconductor detectors. From 2008 to 2011 two instruments were installed in two aircraft. First we corrected the data for pressure variation by normalizing them to one flight level and determined their dependence on the cut-off rigidity by fitting a Dorman function to the observation. The latter was used to compute the yield function, that describes the ratio of incoming primary cosmic rays, approximated by a force field solution, to the measured count and dose rate for a particular instrument. As for neutron monitors the sensitivity increases substantially above a rigidity of about 1 GV.
We received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 870405. 

How to cite: Romaneehsen, L., Burmeister, S., Bernd, B., Herbst, K., Marquardt, J., Senger, C., and Wallmann, C.: Yield function of the DOSimetry TELescope (DOSTEL) count and dose rates aboard an aircraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12121, https://doi.org/10.5194/egusphere-egu22-12121, 2022.

Within the wider scope of improving Space weather forecast by the EUHFORIA project, we present an updated version of the AtRIS code designed to simulate the count rates and dose deposits of space weather events in the atmosphere. As more and more of modern technological infrastructure is sensitive to radiation exposure space weather forecast can develop into a critical tool to protect it from possible damage. Thereby, AtRIS can be applied  to analyse the impact of past Solar Energetic Particle (SEP) events, complementary to the analysis and comparisons of measurements both at top the  atmosphere and at ground level by e.g. NAVIDOS and DOSTEL. AtRIS thereby is designed as a framework of the well established GEANT4 code, offering   the possibility to implement the atmospheric composition in a layer-wise model. Furthermore, it offers the possibility to select the thickness of the  shielding between 0 and 20 mm of aluminium. Here we will present the physics implemented into AtRIS, its validation, and show preliminary results for  selected past events utilising different layers of shielding.The Kiel team received funding from the European Union’s Horizon 2020 research and  innovation programme under grant agreement No 870405.

How to cite: Pohland, P., Vogt, A., Banjac, S., Burmeister, S., Giese, H., Heber, B., Herbst, K., Romaneehsen, L., and Wallmann, C.: Presenting the AtRIS code as a future tool to investigate the atmospheric impactof SEP events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12744, https://doi.org/10.5194/egusphere-egu22-12744, 2022.

During July-October of 2019, a sequence of Corotating Interaction Regions (V_SW ≥ 600 km/s) impacted the magnetosphere, for four consecutive solar rotations. Even though the series of CIRs resulted in relatively weak geomagnetic storms (SYM-H_min ≈ -60 nT, Kp_max ≈ 5), the net effect of the outer radiation belt during each disturbance was different, depending on the electron energy. During the August-September CIR, intense substorm activity was recorded (SML_min ≈ - 2000 nT), as well as significant enhancement of ultra-relativistic electrons.

We exploit coordinated and cross-calibrated particle measurements from the Van Allen Probes, Arase and Galileo 207, 215 satellites, to investigate the relative contribution of radial diffusion and gyro-resonant acceleration, using both electron fluxes and Phase Space Density (PSD) radial profiles, also compared with a 1D Fokker-Planck simulation.

Additionally, we use chorus wave amplitude and radial diffusion coefficient (D_LL) estimations, from the SafeSpace D_LL database, density measurements from the GFZ-Potsdam database, as well as solar wind and geomagnetic parameters, for a detailed investigation of these events.

This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace project.

How to cite: Nasi, A., Daglis, I. A., Katsavrias, C., Sandberg, I., Li, W., Allison, H., Miyoshi, Y., Imajo, S., Mitani, T., Hori, T., Shprits, Y., Kasahara, S., Yokota, S., Keika, K., Shinohara, I., Matsuoka, A., and Kasahara, Y.: Coordinated observations of relativistic electron enhancements following the arrival of consecutive Corotating Interaction Regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-536, https://doi.org/10.5194/egusphere-egu22-536, 2022.

This project aims to provide space weather predictions that will be initiated from observations on the Sun and to predict radiation in space and its effects on satellite infrastructure. Real-time predictions and a historical record of the dynamics of the cold plasma density and ring current allow for evaluation of surface charging, and predictions of the relativistic electron fluxes will allow for the evaluation of deep dielectric charging. The project aims to provide a 1-2 day probabilistic forecast of ring current and radiation belt environments, which will allow satellite operators to respond to predictions that present a significant threat. As a backbone of the project, we use the most advanced codes that currently exist and adapt existing codes to perform ensemble simulations and uncertainty quantifications. This project includes a number of innovative tools including data assimilation and uncertainty quantification, new models of near-Earth electromagnetic wave environment, ensemble predictions of solar wind parameters at L 1, and data-driven forecast of the geomangetic Kp index and plasma density. The developed codes may be used in the future for realistic modelling of extreme space weather events. The PAGER consortium is made up of leading academic and industry experts in space weather research, space physics, empirical data modelling, and space environment effects on spacecraft from Europe and the US.

How to cite: Shprits, Y. Y. and the Horizon 2020 PAGER team: Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-633, https://doi.org/10.5194/egusphere-egu22-633, 2022.

Using observations of Van Allen Probes, we present a statistical study of plasmaspheric plumes in the inner magnetosphere. Plasmaspheric plumes tend to occur during the recovery phase of geomagnetic storms. Furthermore, the results imply that the occurrence rate of observed plasmaspheric plume in the inner magnetosphere is larger during stronger geomagnetic activity. This statistical result is different from the observations of the Cluster satellite with much higher L-shells in most orbital period, which suggest that the plasmaspheric plume near the magnetopause tends to be observed during moderate geomagnetic activity (Lee et al., 2016). In the following, the dynamic evolutions of plasmaspheric plumes during a moderate geomagnetic storm in February 2013 and a strong geomagnetic storm in May 2013 are simulated through group test particle simulation. It is obvious that the plasmaspheric particles drift out on open convection paths due to sunward convection during both geomagnetic storms. It seems that the outer plasmaspheric particles exhaust sooner and the plasmasphere shrinks faster during strong geomagnetic storms. As a result, the longitudinal width of the plume is narrower and the plume is limited to lower L-shells during the recovery phase of strong geomagnetic storm. The simulated evolutions may provide a possible interpretation for the occurrence rates: Van Allen Probes tend to observe plumes during stronger geomagnetic storms, and the Cluster satellite with higher L-shells tends to observe plumes during moderate geomagnetic storms. 

How to cite: Li, H.: Statistical Study and Corresponding Evolution of Plasmaspheric Plumes under Different Levels of Geomagnetic Storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1081, https://doi.org/10.5194/egusphere-egu22-1081, 2022.

Throat auroras frequently observed near local noon have been confirmed to correspond to magnetopause indentations, but the generation mechanisms for these indentations and the detailed properties of throat aurora are both not fully understood. Using all‐sky camera and magnetometer observations, we reported some new observational features of throat aurora as follows. (1) Throat auroras can occur under stable solar wind conditions and cause clear geomagnetic responses. (2) These geomagnetic responses can be simultaneously observed at conjugate geomagnetic meridian chains in the Northern and Southern Hemispheres. (3) The initial geomagnetic responses of throat aurora show concurrent onsets that were observed at all stations along the meridians. (4) Immediately after the concurrent onsets, poleward moving signatures and micropositive bays were observed in the X components at higher‐ and lower‐latitude stations, respectively. We argue that these observations provide evidence for throat aurora being generated by low‐latitude magnetopause reconnection. We suggest that the concurrent onsets reflect the instantaneous responses of the reconnection signal arriving at the ionosphere, the followed poleward moving signatures reflect the antisunward dragging of the footprint of newly opened field lines, and the micropositive bays may result from a pair of field‐aligned currents generated during the reconnection. This study may shed new light on the geomagnetic transients observed at cusp latitude near magnetic local noon.

How to cite: Feng, H.-T., Han, D., Chen, X., Liu, J., and Xu, Z.: Interhemispheric Conjugacy of Concurrent Onset and Poleward Traveling Geomagnetic Responses for Throat Aurora Observed Under Quiet Solar Wind Conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1143, https://doi.org/10.5194/egusphere-egu22-1143, 2022.

Previous studies demonstrated that frequency harmonic structures of fast magnetosonic (MS) waves are usually excited by the hot proton instability. Here, we present an unusual event of MS waves with more than six harmonics wavebands (n = 1–6) in which their high harmonic bands are highly phase-coupled with their fundamental waveband. While calculations of the wave growth rates indicate that the local instability of the hot protons can excite the fundamental waveband (n = 1) as well as only a part of wave branches in the second and third wavebands (n = 2, 3), the bicoherence index adopted to analyze the phase coupling between different wavebands provides evidence that the wave–wave coupling between the low-frequency parts of MS waves can contribute to the generation of their higher harmonics (n > 1). Such wave–wave coupling processes have the potential to additionally redistribute the energy of MS waves and then broaden the frequency range of wave–particle interactions, which has important implications for a better understanding of the generation, distribution, and consequence of space plasma waves.

How to cite: Zou, Z., Gao, Z., Zuo, P., and Ni, B.: Evidence of wave–wave coupling between frequency harmonic bands of magnetosonic waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1426, https://doi.org/10.5194/egusphere-egu22-1426, 2022.

Chorus waves can cause the loss of energetic electrons in the Earth's radiation belts and ring current via pitch-angle diffusion. To quantify the effect of chorus waves on energetic electrons, we calculated the bounce-averaged quasi-linear diffusion coefficients. In this study, using these diffusion coefficients, we parameterize the lifetime of the electrons with an energy range from 1 keV to 2 MeV. In each magnetic local time (MLT), we calculate the lifetime for each energy and L-shell using two different methods. By applying polynomial fits, we parameterize the electron lifetime as a function of L-shell and electron kinetic energy (Ek) in each MLT and geomagnetic activity (Kp). The parameterized electron lifetimes show a strong functional dependence on L-shell and electron energy. During storm time, the lifetimes for higher energy (> 100 keV) electrons range from hours to days in the heart of the radiation belts. In contrast, the lifetimes for electrons with lower energy (< 100 keV) range from minutes to hours. This parameterization of electron lifetime is convenient for inclusion in simulations in the inner magnetosphere. 

How to cite: Wang, D., Shprits, Y., and Haas, B.: Parameterized Lifetime of Energetic Electrons due to Interactions with Chorus Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1546, https://doi.org/10.5194/egusphere-egu22-1546, 2022.

 In this letter, we report an electromagnetic ion cyclotron (EMIC) harmonic event observed by the Van Allen Probe B, whose generation is demonstrated to result from nonlinear wave-wave resonances through the bicoherence analysis. Hybrid simulation shows that the second to sixth harmonics could be excited in sequence after a pump EMIC wave is initially injected, which is in consistent with the observations of EMIC harmonic. It indicates the important role of the second harmonic in the generation of higher harmonics. Finally, the statistical distribution for the amplitude of EMIC second harmonic waves indicates that the energy transfer rate from the fundamental wave to the second harmonic is mainly less than 2%, which might be too low to result in third and other higher harmonics above the observational level. Our results will give some new insights into the excitation of EMIC harmonic waves in the inner magnetosphere.

How to cite: Deng, D., Yuan, Z., Huang, S., Xue, Z., Huang, Z., and Yu, X.: Electromagnetic Ion Cyclotron Harmonic Waves Generated via Nonlinear Wave-Wave couplings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1623, https://doi.org/10.5194/egusphere-egu22-1623, 2022.

The Van Allen Probe B satellite simultaneously observed electromagnetic ion cyclotron (EMIC) and fast magnetosonic (MS) waves in a magnetic dip on April 29, 2017. During the magnetic dip, we found the coexistence of flux enhancements of ring current protons (∼11.2–∼51.7 keV) and flux reductions of relativistic electrons (∼1 MeV), which are identified as typical signatures of a magnetic dip in the inner magnetosphere. Based on linear theoretical calculations and observational analysis, the observed ring current protons show an anisotropic temperature distribution and partial shell distribution for different energies during the magnetic dip to provide free energies for the generation of EMIC and MS waves, respectively. Our findings indicate that the complex unstable distribution in the velocity phase space of ring current protons during the magnetic dip can trigger the simultaneous generation of EMIC and MS waves in the inner magnetosphere.

How to cite: Huang, Z., Yuan, Z., Yu, X., Xue, Z., and Ouyang, Z.: Simultaneous Generation of EMIC and MS Waves During the Magnetic Dip in the Inner Magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1678, https://doi.org/10.5194/egusphere-egu22-1678, 2022.

Via cyclotron resonant interactions, electromagnetic ion cyclotron (EMIC) waves play an important role in the loss of ring current protons. In this study, by calculating the proton bounce-averaged pitch angle diffusion coefficients using both the cold and hot plasma dispersion relations, we investigate the hot plasma effects on the EMIC wave-induced scattering loss of ring current protons. Our results show that, for H⁺ band (He⁺ band) EMIC waves, inclusion of hot protons results in significant decrease of pitch angle diffusion coefficients of ~ 10 - 60 keV (4 - 30 keV) protons, while the scattering efficiency of higher energy protons increases at low pitch angles and decreases at relatively high pitch angles. We also find that the cold plasma approximation seriously underestimates the loss timescales of protons at energies from a few keV to tens of keV but overestimate that of higher energy protons. The differences in proton loss timescales caused by hot plasmas are generally less than a factor of ~ 5 for H⁺ band but can exceed an order of magnitude for He⁺ band, showing a strong dependence on ,  and L-shell. This study confirms that hot plasma effects play a crucial role in the EMIC wave driven loss of ring current protons and should be included in future modeling of ring current dynamics.

How to cite: Zhu, Q., Cao, X., Ni, B., Gu, X., and Ma, X.: Hot Plasma Effects on the Pitch-Angle Scattering of Ring Current Protons by EMIC Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2106, https://doi.org/10.5194/egusphere-egu22-2106, 2022.

A localized flux tube with reduced entropy (PV^5/3, where P and V stand for the plasma pressure and flux tube volume, respectively) as compared to its neighbors is defined as a plasma-sheet bubble. Bubbles are susceptible to interchange instability. The interchange instability plays a key role in the transport of plasma from the magnetotail to the near-Earth region. A strong dawn-to-dusk electric field is formed inside the bubble which creates a shear flow. The E×B drift causes the bubble to grow earthward and the magnetic tension force drives it towards the equilibrium location where its total entropy matches the entropy of the surrounding area. According to the Vasyliunas equation, when the angle (α) between ∇V and ∇PV^5/3 is either 0 (being parallel) or 180^° (being antiparallel), the Birkeland current cannot be flown between the plasma sheet and the ionosphere. In this study, using the linear instability analysis we investigate the excitation and development of interchange modes in the low-beta plasma sheet (β<<1) when 0<α<180^°. To this end, a boundary layer (with thickness δ) separating regions of higher and lower entropy is assumed in a small region of the ionosphere. The first-order electric potential (Φ) within this layer is numerically calculated based on time-sequence technique. The complete analytical solution for the temporal variation of Φ clearly shows that the unstable interchange modes with large wavelengths compared to the boundary layer (i.e., λ>>δ) can be generated.

How to cite: Sadeghzadeh, S., Yang, J., and Mousavi, A.: Interchange instability analysis based on magnetosphere-ionosphere coupling theory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2109, https://doi.org/10.5194/egusphere-egu22-2109, 2022.

Bounce-resonant diffusion coefficients of radiation belt energetic electrons induced by extremely low-frequency (ELF) chorus waves are comprehensively evaluated using Van Allen Probes observations on 22 December 2014. ELF chorus waves can efficiently scatter 85° < _eq < 89° electrons with bounce resonance pitch angle scattering rates above 10^-4/s and energy scattering rates above 10^-7/s. By comparing diffusion coefficients due to bounce resonance with those due to cyclotron and Landau resonances, we found that bounce resonance diffusion rates have slight energy dependence for >100 keV electrons while Landau-resonant scattering rates decrease significantly in the MeV energy range. These findings suggest that bounce resonances by ELF chorus waves have potentially significant contributions to the dynamics of energetic electrons and should be considered in the further modeling of Earth’s radiation belts.

How to cite: Guo, D., Xiang, Z., Ni, B., Cao, X., Fu, S., Zhou, R., Gu, X., Yi, J., Guo, Y., and Jiao, L.: Bounce Resonance Scattering of Radiation Belt Energetic Electrons by Extremely Low-Frequency Chorus Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2136, https://doi.org/10.5194/egusphere-egu22-2136, 2022.

Auroral kilometric radiations (AKR) are existed by suprathermal (1-10keV) electrons, which are accelerated by parallel electric fields and pitch angle scattered by magnetic field gradients. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study of AKR distribution characteristic in the region of λ = 0°−40°and L = 3.0−9.0. Results (totally 32,043 samples) show that southern AKR on the nightside (12,853 samples) are positioned to the east relative to their northern conjugates (13,630 samples), the wave frequencies and amplitudes of AKR in the southern hemisphere are greater than those in the northern hemisphere. Further studies suggest that SYM-H indexes and interplanetary magnetic field (IMF) have different distributions in the northern and southern hemispheres. The probable reason is that different IMF conditions cause asymmetric Field-aligned currents between the northern and southern hemispheres, then yield the asymmetry of AKR and auroras. This study helps to provide more information on the magnetosphere-ionosphere-atmosphere coupling.

How to cite: Tang, J., Xiao, F., Liu, S., and Zhang, S.: Asymmetry of Auroral Kilometric Radiation in the Northern and Southern hemispheres, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3288, https://doi.org/10.5194/egusphere-egu22-3288, 2022.

Auroral kilometric radiation (AKR) is one of the strong radio emission phenomenons with kilometer wavelengths, and similar emissions have been detected on other magnetized planets of the solar system. AKR is generated by suprathermal electrons (1-10 keV) injected from the plasma sheet and has been observed at the lower latitude region of the radiation belts from the Van Allen Probes. Here, we analyze the seasonal characteristic of AKR in the region of L = 3-7 and λ = 0^◦− 20^◦ using observations from 1 December 2012 to 31 November 2018. Statistical results (4,559 events in total) show that AKR emissions occur most frequently in autumn both in the northern and southern hemispheres. The correlation coefficient between the number of AKR events in each season and the Kp (the geomagnetic activity index) index of these events can reach 0.82. These results suggest that AKR emissions in the lower latitude regions depend on the geomagnetic activity.

How to cite: Li, P., Xiao, F., Liu, S., and Zhang, S.: Seasonal Characteristic of Auroral Kilometric Radiation in the Radiation Belts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4043, https://doi.org/10.5194/egusphere-egu22-4043, 2022.

In this study, we present simultaneous multi-point observations of whistler-mode chorus waves and global magnetospheric oscillations on a timescale of several to ~10s minutes (breathing mode magnetic field oscillations), associated with concurrent energetic electron precipitation observed through enhanced BARREL X-rays. Similar fluctuations on a timescale of several to ~10s minutes are observed in the X-ray measurements and the compressional component of global oscillations. The spatial scale of global oscillations spans from 4 to 12 h in MLT and from 5 to 11 in L shell. Such global oscillations, which have been suggested to play a potential role in precipitating energetic electrons by either wave scattering or loss cone modulation, show high correlation with the enhancement in X-rays. However, the correlation coefficient between whistler-mode waves and X-rays is low. Observations and model results show that the breathing-mode magnetic field oscillations could play a significant role in modulating the electron precipitation driven by whistler-mode waves even though the whistler-mode wave intensity is not fully modulated by global oscillations.

How to cite: Qin, M., Li, W., Ma, Q., Shen, X., and Shen, X.: Global magnetic field oscillations on the breathing-mode timescale and their effects on energetic electron precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4057, https://doi.org/10.5194/egusphere-egu22-4057, 2022.

The European SafeSpace project has been implementing a synergistical approach to improve space weather forecasting capabilities from the current lead times of a few hours to 2-4 days. We have combined the solar wind acceleration model MULTI-VP with the heliospheric propagation models Helio1D and EUHFORIA to compute the evolution of the solar wind from the surface of the Sun to the Earth orbit. The forecasted solar wind conditions are then fed into the ONERA Geoffectiveness Neural Networks, to forecast the level of geomagnetic activity with the Kp index as the chosen proxy. The Kp index is used as the input parameter for the IASB plasmasphere model and for the Salammbô radiation belts code. The plasma density is used to estimate VLF wave amplitude and then VLF diffusion coefficients, while the predicted solar wind parameters are used to estimate the ULF diffusion coefficients. Plasmaspheric density and VLF/ULF diffusion coefficients are used by the Salammbô radiation belts code to deliver a detailed flux map of energetic electrons. Finally, particle radiation indicators will also be provided as a prototype space weather service of use to spacecraft operators and space industry. The performance of the prototype service will be evaluated in collaboration with space industry stakeholders. The work leading to this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace (Radiation Belt Environmental Indicators for the Safety of Space Assets) project.

How to cite: Daglis, I. A. and the SafeSpace Team: Advanced Prediction of the Outer Van Allen Belt Dynamics and a Prototype Service: the H2020 SafeSpace project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6518, https://doi.org/10.5194/egusphere-egu22-6518, 2022.

Radial diffusion has been established as one of the most important mechanisms contributing to the acceleration and loss of relativistic electrons in the outer radiation belt. Over the past few years efforts have been devoted to identify empirical relationships of radial diffusion coefficients (D_LL) for radiation belt simulations, yet several studies have suggested that the difference between the various models can be orders of magnitude different at high levels of geomagnetic activity, as the observed DLL have been shown to be highly event-specific. In the framework of the SafeSpace project we have used 12 years (2010 – 2020) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of calculated DLL. In this work we present the statistics on the evolution of DLL during the solar cycle 24 with respect to the various solar wind parameters, geomagnetic indices and universal coupling functions. Furthermore, we show the importance of the use of event-specific DLL through simulations of seed and relativistic electrons with the Salammbo code during the intense storm of St. Patricks 2015 and the high-speed stream driven storm of Christmas 2013. Finally, we present a new approach for a Machine Learning model driven solely by Solar wind parameters.

This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437.

How to cite: Daglis, I. A., Katsavrias, C., Aminalragia-Giamini, S., Nasi, A., Dahmen, N., Brunet, A., Bourdarie, S., and Papadimitriou, C.: Radial diffusion coefficients database in the framework of the SafeSpace project: A Machine Learning model and the application to radiation belt simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6555, https://doi.org/10.5194/egusphere-egu22-6555, 2022.

We present a machine-learning-based model of relativistic electron fluxes >1.8 MeV using a neural network approach in the Earth's outer radiation belt. The Outer RadIation belt Electron Neural net model for Relativistic electrons (ORIENT-R) uses only solar wind conditions and geomagnetic indices as input. For the first time, we show that the state of the outer radiation belt can be determined using only solar wind conditions and geomagnetic indices, without any initial and boundary conditions. The most important features for determining outer radiation belt dynamics are found to be AL, solar wind flow speed and density, and SYM-H indices. ORIENT-R reproduces out-of-sample relativistic electron fluxes with a correlation coefficient of 0.95 and an uncertainty factor of ∼2. ORIENT-R reproduces radiation belt dynamics during an out-of-sample geomagnetic storm with good agreement to the observations. In addition, ORIENT-R was run for a completely out-of-sample period between March 2018 and October 2019 when the AL index ended and was replaced with the predicted AL index (lasp.colorado.edu/home/personnel/xinlin.li). It reproduces electron fluxes with a correlation coefficient of 0.92 and an out-of-sample uncertainty factor of ∼3. Furthermore, ORIENT-R captured the trend in the electron fluxes from low-earth-orbit (LEO) SAMPEX, which is a completely out-of-sample data set both temporally and spatially. In sum, the ORIENT-R model can reproduce transport, acceleration, decay, and dropouts of the outer radiation belt anywhere from short timescales (i.e., geomagnetic storms) and very long timescales (i.e., solar cycle) variations.

How to cite: Chu, X., Ma, D., Bortnik, J., Tobiska, W. K., Cruz, A., Bouwer, S. D., Zhao, H., Ma, Q., Zhang, K., Baker, D. N., Li, X., Spence, H., and Reeves, G. D.: A Neural Network-Based Model of the Relativistic Electrons Fluxes in the Outer Radiation Belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6611, https://doi.org/10.5194/egusphere-egu22-6611, 2022.

Electron cyclotron harmonic (ECH) waves which mainly observed in the first harmonic band are believed to play a part in scattering diffuse aurora electrons in the Earth's magnetosphere. Here we report two enhanced ECH emission events with nominal wave magnitudes exceeding 1mV/m in higher bands ( up to the 4^th harmonic bands) observed from Van Allen Probes mission during geomagnetic disturbance periods in the low density area. Based on actual measurements sampled by Van Allen Probes, we model the electron distribution using a superposition of bi-Maxwellian functions and then numerically evaluate the local growth rates and diffuse coefficients. These differences in frequency distribution for two events can be explained by differences in the loss cone feature of hot electron components. The scattering properties in the first four bands for two events are debated, these results suggest ECH waves in higher band can still cause efficient pitch angle scattering which are similar to ECH waves in the first band. This work broadens our understanding in the formation of diffuse aurora contributed by ECH waves.

How to cite: Qiwu, Y., Fuliang, X., Qinghua, Z., Si, L., Zhonglei, G., Yihua, H., Sai, Z., Zhoukun, D., and Jiawen, T.: Observations of Higher-band ECH waves and its impact on radiation belt energetic electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6712, https://doi.org/10.5194/egusphere-egu22-6712, 2022.

Subauroral polarization streams (SAPS) typically refer to an enhanced westward plasma flow channel in the duskside subauroral ionosphere. SAPS overlap with the low-latitude part of downward Region-2 field-aligned currents (FACs). The relatively low subauroral conductance in this region requires a strong electric field for current closure, which drives the fast sunward plasma flow. Observations have shown dynamic variability of SAPS under various solar wind and interplanetary magnetic field (IMF) conditions, which are related to the variability of FACs and auroral precipitation, as well as their source regions in the ring current and plasmasheet. In this study, we use satellite observations and numerical simulations with the state-of-the-art Multiscale Atmosphere Geospace Environment (MAGE) model to investigate: 1) The role of diffuse electron precipitation in the formation of SAPS; 2) SAPS variability under IMF B_Y; and 3) Dawnside (as opposed to the more conventional duskside) SAPS as a unique feature of major geomagnetic storms. With data-model comparison, we will demonstrate that SAPS result from the different behaviors of ring current ions and plasma sheet electrons, and the corresponding self-consistent response of the ionosphere-thermosphere system via electrodynamic and particle coupling with the magnetosphere. We conclude that SAPS distribution and variability represent a fundamental feature of the geospace response to solar disturbances during storm time.

How to cite: Lin, D., Wang, W., Merkin, V., Wiltberger, M., Sorathia, K., Pham, K., Bao, S., Michael, A., Shi, X., Huang, C., Wu, Q., Zhang, Y., Oppenheim, M., Toffoletto, F., Lyon, J., Garretson, J., and Anderson, B.: Subauroral polarization streams (SAPS): Intrinsic response of geospace during storm time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6869, https://doi.org/10.5194/egusphere-egu22-6869, 2022.

Low-energy ring current electrons of up to 50 keV represent a major threat to spacecrafts within the inner magnetosphere since they are one of the main causes of spacecraft surface charging. Furthermore, they can provide a seed population for relativistic radiation belt electrons during geomagnetic storms. In this work, we report the first results of coupling the Versatile Electron Radiation Belt (VERB) code with a fully MLT resolved physics-based plasmasphere model to investigate the loss mechanisms of low energy electrons. Our four dimensional ring current model used in this study includes radial diffusion, convection, and loss due to whistler-mode chorus and hiss waves. The physics-based model of the plasmasphere includes convection of cold plasma and refilling from the ionosphere.
We simulate two storm events from the Van Allen Probes' era and compare results of cold plasma density and electron flux against measurements from the twin Van Allen Probe satellites. Our plasmasphere model is not only capable of predicting the plasmapause location but also the formation of plasmaspheric plumes, where plume whistler mode waves propagate. Including the plume region, which usually has very restricted spatial coverage, allows us to examine the effect of plume whistler mode waves on the loss of ring current electrons during these two events. These plasma boundaries show significant dynamics during the main and recovery phase of storms and are crucial to correctly predict electron loss.
By using the extracted plasma boundaries to determine the spatial extent of different waves species, we find better agreement of electron flux results with measurements, especially during the main phase of storms. We also report on the first ring current simulation results including the loss introduced by spatially localised whistler-wave scattering in plasmaspheric plumes.

How to cite: Haas, B., Shprits, Y., Wutzig, M., Allison, H., and Wang, D.: The Effect of Plasmaspheric Plumes on the Loss of Ring Current Electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7570, https://doi.org/10.5194/egusphere-egu22-7570, 2022.

Ring current particles affect the terrestrial magnetic field configuration, altering particle trajectories, as well as presenting a surface charging hazard for satellites. These particles can act as a seed population for the electron radiation belts and generate plasma waves. Accurately describing ring current dynamics is crucial to understand the near-Earth plasma environment. Here we report on our first results of the expansion of the Versatile Electron Radiation Belt (VERB) code to model ring current proton dynamics (proVERB). We perform sensitivity studies for the four dimensional grid, considering the grid resolution necessary to resolve proton dynamics. Analysing the banana shaped orbits for ring current protons shows that the azimuthal grid resolution is comparable to the electron grid, while the resolution in the radial grid has to be significantly enhanced. Loss mechanisms of charge exchange and Coulomb collisions, thought to be largely responsible for the decay of the ring current during the recovery phase of a storm, are included in proVERB. We present our first simulation results and compare them to observations from the Van Allen probes HOPE and MagEIS instruments. By retaining and omitting charge exchange and Coulomb collisions in our simulations, we study the role of these loss processes on the ring current evolution during active periods.

How to cite: Himmelsbach, J., Allison, H., Shprits, Y., Haas, B., Wutzig, M., and Wang, D.: Assessing the contribution of charge exchange and Coulomb collisions to ring current proton dynamics with the new 4-D Proton Versatile Electron RadiationBelt (proVERB) code, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7578, https://doi.org/10.5194/egusphere-egu22-7578, 2022.

Pitch angle distributions (PADs) of trapped particles play an important role in understanding the processes driving the dynamics of Earth’s radiation belts and ring current. The Van Allen Probes mission has provided electron observations of PADs with an unprecedented coverage in energy (from tens of keV to several MeV) and pitch angles during the mission’s lifespan. We approximate the equatorial electron PADs using the Fourier sine series expansion up to degree 5. The corresponding coefficients can be directly related to the main PAD shapes (pancake, butterfly, flat-top and cap), and the approximated PADs can be easily integrated and converted to omnidirectional flux. Using the entire Van Allen Probes MagEIS data set in 2012-2019, we analyze the response of the equatorial electron PAD shapes to 129 geomagnetic storms with minimum Dst< -50nT. At lower energies (<100 keV), the PADs are stable throughout geomagnetic storms and mainly exhibit a pancake shape. At higher energies, the storm-time PAD evolution depends on the magnetic local time (MLT). At dayside, the pancake distributions become steeper during the main phase and then recover to their original broader form during recovery phase, likely due to the inward radial diffusion. At nightside MLT, the butterfly distributions become more pronounced during the main phase due to the combination of drift-shell splitting and magnetopause shadowing. We present a simple polynomial regression model of PAD shapes driven by the solar wind dynamic pressure. The model allows reconstructions of the full equatorial PADs based on uni-directional measurements at low equatorial pitch angles (applicable to LEO satellite data), as well as from omnidirectional electron flux observations and significantly outperforms the standard sin(alpha) approximation.

How to cite: Smirnov, A., Shprits, Y., Allison, H., Aseev, N., Drozdov, A., Kollmann, P., Wang, D., and Saikin, A.: Equatorial electron pitch angle distributions in Earth's outer radiation belt: Storm-time evolution and empirical modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7732, https://doi.org/10.5194/egusphere-egu22-7732, 2022.

Protons of tens of keV can be resonantly scattered by EMIC waves excited in the magnetosphere and further precipitate down to the upper atmosphere. In this study, we show a case event that shows direct linkage of the EMIC waves, proton precipitation, and ionospheric ionization using space-borne and ground-based measurements. On Oct 11, 2012, the POES observed that the precipitating flux of the proton much larger than that of the electrons in the night sector around magnetic latitude of 65°. Around the same time and location, ground-based magnetometer detected clear signature of EMIC waves, indicating the causal relation to the proton precipitation. We further simulate the impact of this tens of keV proton precipitation on the upper atmosphere, and found good agreement with PFISR observations of electron density and conductivity. On the other hand, the large ionization rate cannot be accounted for by the electron precipitation at that location. This study shows a clear evidence of the precipitating coupling processes within the magnetosphere-ionosphere system.

How to cite: Tian, X., Yu, Y., and Ma, L.: The EMIC wave-driven proton precipitation and related effects on the ionosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8485, https://doi.org/10.5194/egusphere-egu22-8485, 2022.

Properly characterizing fast relativistic electron losses in the terrestrial Van Allen belts remains a significant challenge for accurately simulating their dynamics. In particular, magnetopause shadowing losses can deplete the radiation belt within hours or even minutes but can have long-lasting impacts on the subsequent belt dynamics. By statistically analyzing seven years of data from the entire Van Allen Probes mission in the context of the last closed drift shell, here we show how these losses are much more organized and predictable than previously thought. Once magnetic storm electron dynamics are properly analyzed in terms of the location of the last closed drift shell, not only is the loss shown to be repeatable but its energy-dependent spatio-temporal evolution is also revealed to follow a very similar pattern from storm to storm. Employing an energy-dependent ULF wave radial diffusion model, we further show for the first time how the similar and repeatable fractional loss of the pre-storm electron population in each storm can be reproduced and explained. Empirical characterization of this loss may open a pathway toward improved radiation belt specification and forecast models. This is especially important since underestimates of loss can also create unrealistic sources in models, creating phantom electron radiation and leading to the prediction of an overly harsh radiation environment.

How to cite: Olifer, L., Mann, I., Ozeke, L., Claudepierre, S., Baker, D., and Spence, H.: On the Similarity and Repeatability of Fast Magnetopause Shadowing Loss, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8799, https://doi.org/10.5194/egusphere-egu22-8799, 2022.

Resonant scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms of relativistic electron losses in the inner magnetosphere. For the majority of observed waves, such scattering is well described by the quasi-linear diffusion theory. Low-altitude spacecraft measurements, however, often show that the energy range of precipitating electrons is wider than theoretical predictions based on the cold plasma dispersion of EMIC waves. We develop a hot plasma model based on the observed ion distribution functions and investigate the hot plasma effects on EMIC wave dispersion for a wide frequency range. The results obtained from the analytical hot plasma model agree very well with the numerical solution of the exact dispersion relation of EMIC waves for a wide range of plasma parameters. We also show the implementation of this model for diffusion rate evaluation. Combining near-equatorial spacecraft measurements and wave dispersion model, we show that hot ion effects tend to increase the minimum resonant energy for the frequency range around wave intensity maxima, but can decrease the minimum resonant energy for the higher-frequency part of wave spectra.

This study highlights the importance of hot plasma effects on the relativistic electron scattering and provides a hot plasma model applicable to a wide range of plasma parameters for realistic quasi-linear diffusion rate calculations.

How to cite: Bashir, M. F., Artemyev, A., Zhang, X., and Angelopoulos, V.: Relativistic electron scattering by electromagnetic ion cyclotron waves: the hot plasma Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8840, https://doi.org/10.5194/egusphere-egu22-8840, 2022.

Quantification of energetic electron precipitation caused by wave-particle interactions is fundamentally important to understand the cycle of particle energization and loss of the radiation belts. One important way to determine how well the wave-particle interaction models predict losses through pitch-angle scattering into the atmospheric loss cone is the direct comparison between the ionization altitude profiles expected in the atmosphere due to the precipitating fluxes and the ionization profiles actually measured with incoherent scatter radars. This paper reports such a comparison using a forward propagation of loss-cone electron fluxes, calculated with the electron pitch angle diffusion model applied to Van Allen Probes measurements, coupled with the Boulder Electron Radiation to Ionization (BERI) model, which propagates the fluxes into the atmosphere. The density profiles measured with the Poker Flat Incoherent Scatter Radar operating in modes especially designed to optimize measurements in the D-region, show multiple instances of quantitative agreement with predicted density profiles from precipitation of electrons caused by wave-particle interactions in the inner magnetosphere. There are two several-minute long intervals of close prediction-observation approximation in the 65-93 km altitude range. These results indicate that the whistler wave-electron interactions models are realistic and produce precipitation fluxes of electrons with energies between 10 keV to >100 keV that are consistent with observations.

How to cite: Sanchez, E., Ma, Q., Xu, W., Marshall, R., Bortnik, J., Reyes, P., Varney, R., and Kaeppler, S.: A Test of Energetic Particle Precipitation Models Using Simultaneous Incoherent Scatter Radar and Van Allen Probes Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8977, https://doi.org/10.5194/egusphere-egu22-8977, 2022.

Electromagnetic ion cyclotron (EMIC) wave plays an important role in precipitating relativistic electrons. In this study, we analyze an EMIC wave event on 6 November 2015 that extended over 6 hours in local time and the amplitude of this EMIC wave is about 3nT. Solar wind dynamic pressure enhancement excites EMIC waves, and whistler mode chorus waves are observed at the same time. When the EMIC wave occurs, the flux of relativistic electrons with pitch angle around 90° increases and the flux of small-pitch-angle relativistic electrons decreases. We calculate the electron PSD, which proves that EMIC wave leads to relativistic electron precipitation. Our result indicates that the large-amplitude EMIC wave will lead to nonlinear wave-particle interaction, thus leading to relativistic electron precipitation. When the wave amplitude is larger, the nonlinear wave-particle interaction becomes stronger.

How to cite: Yan, Y. and Yue, C.: EMIC Waves Induced by the Enhancement of Solar Wind Dynamic Pressure and Subsequent Relativistic Electron Precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9034, https://doi.org/10.5194/egusphere-egu22-9034, 2022.

Geomagnetic storms are the main component of space weather and are driven by coronal mass ejections (CMEs) or corotating interaction regions (CIRs). During the main phase of geomagnetic storms, the ring current enhances and a global decrease in the H component of the geomagnetic field is observed. The storm time distribution of ring current ions and electrons in the inner magnetosphere depend strongly on their transport in evolutions of electric and magnetic fields along with acceleration and loss. Recently, we showed that the electron pressure contributes to the depression of ground magnetic field during the storm time by comparing Ring current Atmosphere interactions Model with Self Consistent magnetic field (RAM-SCB) simulation, Arase in-situ plasma/particle data, and ground-based magnetometer data [Kumar et al., 2021]. In this study, we compare the contribution of electron pressure to the ring current during selected CIR and CME geomagnetic storms using ground observations and the self-consistent inner magnetosphere model: RAM-SCB. The previous results show that the ions are the major contributor (~ 90 %) to the total ring current and the electron contributes ~10 % to the ring current pressure in the post-midnight to dawn sector where electrons flux is higher compared to ions flux. As CIR and CME storms have different origins, we will discuss expected differences in the contribution of electron pressure to the ring current.

How to cite: Kumar, S., Miyoshi, Y., Jordanova, V. K., Engel, M., Asamura, K., Yokota, S., Kasahara, S., Kazama, Y., Wang, S.-Y., Mitani, T., Keika, K., Hori, T., Jun, C.-W., and Shinohara, I.: A comparative study on electron contribution to the ring current during CME and CIR driven geomagnetic storms using RAM-SCB simulations and Arase and ground magnetic data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9039, https://doi.org/10.5194/egusphere-egu22-9039, 2022.

The plasma properties in the inner magnetosphere play critical roles in plasma dynamics by changing magnetic field configurations and generating the ring current. Geomagnetic substorms, especially intense substorms can significantly influence inner magnetosphere. This study presents our preliminary statistical results of plasma properties and their substorm dependence at the equatorial plane based on the Van Allen Probe observations. We find that both H+ and O+ pressure increases significantly during substorms, and the pressure ratio of O+ to H+ also increases. The peak of H+ pressure is almost fixed around L=4, while that of O+ moves inward as the substorm intensifies. In addition, substorms can significantly change the ion energy distributions. They will increase the proportion of pressure provided by the lower energy components of H+ (E < ~100keV), especially in lower L-shells. At the same time, they decrease the contribution to the plasma pressure from lower energy components of O+, which shows almost no L-shell dependence. During quiet times, the perpendicular current density distributes roughly symmetrically, with negative value inside (L < ~4.5) and positive value outside. During substorms, the current density enhances and shows asymmetry with higher current density from the pre-dusk to the post-midnight. The parallel current density caused by the pressure gradient also increases with substorms. These field-aligned currents (FACs) enter the ionosphere at dusk and move upward at dawn, as region II FAC.

How to cite: Fu, H., Yue, C., Zong, Q., and Zhou, X.: Substorm influences on plasma properties distributions in the inner magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9045, https://doi.org/10.5194/egusphere-egu22-9045, 2022.

Our case study aims at contributing to the discussion on sources of plasmaspheric hiss, which is known for its interactions with the Earth radiation belts. We analyze multi-point measurements of electromagnetic field waves by the Wide Band Data instruments onboard the four Cluster spacecraft in order to find sources of hiss observed close to the geomagnetic equator in the dayside outer plasmasphere. We find hiss to be triggered from whistlers of different spectral properties. Whistlers with the lowest observed dispersion arrive to different spacecraft with time delays indicating their origin in the northern hemisphere. Positions of source lightning discharges are then found using the time coincidences with the Word Wide Lightning Location Network data from three active thunderstorm regions in Europe. We find that subionospheric propagation of lightning atmospherics is necessary to explain the observations. Geographic locations of their ionospheric exit points then determine spectral properties of resulting unducted whistlers and triggered hiss. By this well documented chain of events starting with a lightning discharge in the atmosphere we confirm that magnetospherically reflecting whistlers and hiss triggered from them are among possible sources of plasmaspheric hiss.

How to cite: Santolík, O., Kolmašová, I., Pickett, J. S., and Gurnett, D. A.: Coupling of lightning generated electromagnetic waves to the inner magnetosphere: a case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9063, https://doi.org/10.5194/egusphere-egu22-9063, 2022.

How to cite: García Peñaranda, M.: Ring Current Reconstruction via Multi-Satellite Observations and Comparison with VERB-4D Reanalysis Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9530, https://doi.org/10.5194/egusphere-egu22-9530, 2022.

The Earth’s outer radiation belt response to geospace disturbances is extremely variable spanning from a few hours to several months. In addition, the numerous physical mechanisms, which control this response, depend on the electron energy, the time-scale and the types of geospace disturbances. As a consequence, the various models that currently exist are either specialized, orbit-specific data-driven models, or sophisticated physics-based ones. In this paper we present a new approach for radiation belt modelling using Machine Learning methods driven solely by solar wind speed and pressure, Solar flux at 10.7 cm and the Russell-McPherron angle. We use Van Allen Probes data to train our model and show that it can successfully reproduce and predict the electron fluxes of the outer radiation belt in a broad energy (0.033–4.062 MeV) and L-shell (2.5–5.9) range and, moreover, it can capture the long-term modulation of the semi-annual variation. We also present validation studies of the model’s performance using data from other missions which are outside the spatio-temporal training regime such as the E>0.8 MeV electron flux measurements from GOES-15/EPEAD at geostationary orbit.

This work has received funding from the European Union’s Horizon 2020 research and innovation programme "SafeSpace" under grant agreement No 870437 and from the European Space Agency under the "European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System" activity under ESA Contract No 4000127282/19/NL/IB/gg.

How to cite: Aminalragia-Giamini, S., Katsavrias, C., Papadimitriou, C., Daglis, I., Sandberg, I., and Jiggens, P.: Radiation belt model including semi-annual variation and Solar driving (SENTINEL), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9577, https://doi.org/10.5194/egusphere-egu22-9577, 2022.

Interplanetary (IP) shocks in general have strong impact on particles and electromagnetic field. In this study, we have examined the dynamics of cross-energy ions and plasma waves observed by the Van Allen Probe B satellite which was located near the equator at the noon sector after the impact of an IP shock on 27 Feb, 2014. We found that the ULF waves and electromagnetic waves are induced and the differential fluxes of protons with different energies increased or decreased after the IP shock arrival. For low energy ions (10-100eV), the perpendicular flux increased intensively due to ExB drift and betatron acceleration. These adiabatic processes also accounted for the special behavior of 10~200 keV ions, which are due to the positive gradient in phase space density before the IP shock arrival. In addition, the short-lived ultra-low frequency waves triggered by the IP shock interacted with the ~100 keV protons and resulting in the stripes in pitch angle distribution. Meanwhile, the anisotropic ions of ~50-300 keV generate EMIC wave at higher L shell after the shock arrival. This study reveals that an IP shock event can cause comprehensive responses of different energy ions and drive several plasma waves at the same time.

How to cite: Li, Y., Yue, C., Zong, Q., and Zhou, X.: Simultaneous Cross-energy Ion Response and Wave Generation after An Interplanetary Shock: A Case Study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9648, https://doi.org/10.5194/egusphere-egu22-9648, 2022.

Magnetopause perturbations by solar wind transients drive a wide variety of ultra-low-frequency (ULF) waves in the Earth’s magnetosphere. Compressional ULF waves modulate thermal and energetic electron fluxes, changing their flux anisotropy. Such modulation may move electron distributions beyond the threshold of instabilities and drive the generation of electron cyclotron harmonic (ECH) and whistler-mode waves. Given the importance of ECH and whistler-mode waves for electron scattering into the atmosphere, we statistically investigate the main characteristics of ULF-modulated ECH and whistler-mode waves. We find two main types of events: with the correlation of whistler-mode and ECH waves and with their anti-correlation. We present the spatial distribution of these two types of events and examine correlations of background plasma/magnetic field characteristics with properties of whistler and ECH waves modulated by ULF waves.

How to cite: Waheed, A., Bashir, M. F., Artemyev, A., and Zhang, X.: Whistler and electron cyclotron harmonic waves at the near-Earth dayside plasma sheet: statistics of modulation by ultra-low frequency waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11179, https://doi.org/10.5194/egusphere-egu22-11179, 2022.

Energetic electron scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms of electrons losses in the inner magnetosphere. Such resonant scattering has been traditionally considered as a controlling process for the dynamics of relativistic electron fluxes in the Earth’s radiation belts. EMIC wave generation is mainly associated with the ring current ion population injected from the plasma sheet. These ions are drifting westward and generate the most intense EMIC waves on the dusk flank. In this work, we consider an alternative mechanism of EMIC wave generation due to local plasma compression by strong ultra-low-frequency (ULF) waves that modulate a quasi-periodical ion anisotropy responsible for EMIC excitation. Using THEMIS spacecraft observations of simultaneous EMIC waves and compressional ULF waves, we investigate the statistical properties of such quasi-periodic EMIC emission. We show spatial distributions of ULF-modulated EMIC waves, statistics of their amplitudes and typical frequencies. We also discuss the associated measurements of ULF-modulated hot ion populations responsible for EMIC wave generation.

How to cite: Shahid, M., Bashir, M. F., Artemyev, A., Zhang, X., Angelopoulos, V., and Murtaza, G.: Properties of quasi-periodical emission of electromagnetic ion cyclotron waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11316, https://doi.org/10.5194/egusphere-egu22-11316, 2022.

In this study, we present in-situ measurement by Van Allen Probes showing that surface wave could oscillate the plasmapause and modulate hiss and electron cyclotron harmonic (ECH) waves. Plasmapause sur-face wave (PSW) in Ps6 band was observed during an intense substorm on 16 July 2017, accompanied with quasi-periodic emissions of hiss (positively correlated to plasma density) and ECH waves (anticorrelated to the density). Phase relation between magnetic field and velocity perturbations indicatesthat the PSW was an eigenmode between southern and northern ionosphere. Measurements from ground-based magnetometers suggest that such PSW propagates sunward at dusk flank and were excited around the expansion phase of an intense substorm. Addiational cases of PSWs are also presented to demonstrate that such waves are commonly observed near plasmapause and are likely to be related to substorm activities.

How to cite: Hao, Y., Zong, Q., Yue, C., Zhou, X., Zhang, H., Pu, Z., and Shprits, Y.: Plasmapause Surface Waves Triggered by Substorms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11579, https://doi.org/10.5194/egusphere-egu22-11579, 2022.

Whistler chorus waves cause energetic electron precipitations into the Earth’s atmosphere, and signatures of precipitations are observed as diffuse,
pulsating aurora, and microbursts of energetic electrons. In this talk, we present our model that propagating chorus waves cause wide energy electron precipitations and relativistic electron microbursts are a high-energy tail of the pulsating aurora electrons. The chorus waves can resonate with tens keV electrons near the magnetic equator, which causes the pulsating aurora emissions, while the chorus waves can resonate with sub-relativistic/relativistic electrons at the off-equator, which cause the microbursts of energetic electrons. Moreover, we discuss that relativistic electrons cause a significant ozone destruction at the middle atmosphere by conjugate observations of Arase, ground-based observations, SIC ion chemistry simulation.

How to cite: Miyoshi, Y., Saito, S., Hosokawa, K., Asamura, K., Oyama, S., Mitani, T., Sakanoi, T., Kero, A., Turunen, E., and Verronen, P.: Energetic electron precipitations by chorus waves and its impact on the middleatmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11822, https://doi.org/10.5194/egusphere-egu22-11822, 2022.

It is demonstrated that the application of a height-integrated conductivity (HIC) boundary condition in theories of the ionospheric feedback instability is valid only for very thin (few km) conducting layers. In the presence of global convection, the strong variation of the ion mobility with altitude produces strongly sheared transverse ion flows within the E-layer.  These flows are not accounted for when the HIC boundary condition is applied, and when accounted for they cause a drastic reduction in growth rates of the IFI even for very large convection electric fields on the order of a few hundred mV/m. Thie reduction in IFI growth rates is verified through linear eigenmode analysis of the IFI similar to Watanabe & Maeyama (JGR, 45, 2018), except that (a) parallel electric fields in the ionosphere are accounted for, and (b) collision frequency profiles are determined from the IRI and MSIS models (Sydorenko and Rankin, GRL, 44, 2017).

The IFI in field line resonances (FLRs) and the ionospheric resonator (IAR) is studied for a collisional slab ionosphere of thickness 300 km. Constant density is assumed for FLRs, with the slab adjoining a collisionless plasma embedded in a constant magnetic field. Symmetry boundary conditions are applied at the equatorial magnetosphere. In the IAR study, the density varies with altitude and reflecting boundary conditions are used. Instability growth rates are computed numerically and compared with results for slabs of varying thickness (2 km to 300 km) and identical height-integrated conductivity. Growth rates for the most unstable mode are significantly reduced compared to the HIC case for layers as thin as 2 km, even in the long parallel wavelength limit.

The parallel electric field obtained from Faraday’s Law is strongly stabilizing for short transverse wavelength perturbations, especially for higher harmonics. A new unstable mode is found that does not require reflection of  waves within the IAR. It satisfies the resonance condition ω=k_y<V_d> where k_y is the transverse wavelength and <V_d> is the average ion drift velocity within the sptaially structured E-layer. The physical implication of this newly identified ionospheric instability is considered in the context of discrete auroral arcs and field line resonances.

How to cite: Rankin, R., Sydorenko, D., and Shen, W.: A new interpretation of the ionospheric feedback instability applied to feld line resonances and the ionospheric Alfven resonator, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13019, https://doi.org/10.5194/egusphere-egu22-13019, 2022.

The Earth is cooling down and its surface heat flux is the highest among all the terrestrial planet of the Solar System. The total heat loss (Q) is due to the energy released by the secular cooling of our planet (C) and of the radiogenic heat (H) produced by the radioactive decays of the radioelements contained therein. Can geoneutrino disentangle these two contributions?

Since while decaying, the uranium, thorium and potassium radioisotopes contained in the Earth release geoneutrinos in a well-fixed ratio, we can attempt to answer affirmatively to this question. Indeed, geoneutrinos are able to pass through most matter without interacting, so they can bring to surface useful information about the Earth’ deep interior. Concretely, measuring the geoneutrino flux at surface hence translates in estimating H and in turn constraining C once that Q is known.

The only two experiments which collected data in the last 15 years are KamLAND (Japan) and Borexino (Italy). By combining theoretical models and experimental flux with a sophisticated analysis, we inferred valuable insights on mantle radioactivity and of contribution of H to the Earth’s energy budget. We estimated a total radiogenic heat accounting for H = 20.8^+7.3_-7.9 TW and, by subtracting this value from the total heat power of the Earth, we derived a secular cooling C = 26 ± 8 TW. The obtained results are discussed and framed in the puzzle of the diverse classes of formulated Bulk Silicate Earth models, analyzing their implications on planetary heat budget and composition.

The effectiveness in investigating deep earth radioactivity demonstrated by geoneutrino studies confer them a prestigious role in the comprehension of geodynamical processes of our planet.

How to cite: Strati, V., Bellini, G., Inoue, K., Mantovani, F., Serafini, A., and Watanabe, H.: Studying the Earth’s heat budget with geoneutrinos, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-490, https://doi.org/10.5194/egusphere-egu22-490, 2022.

            Ferropericlase is the second most abundant phase of Earth’s lower mantle and is also considered to be one of the main constituents of the mantles of super-Earth exoplanets. Since ferropericlase is more ductile compared to silicates (Girard et al. 2016), it is expected to control the rheological behavior of mantle aggregates which governs solid-state convection of planetary mantles. The mechanical behavior of polycrystalline aggregates is strongly affected by the presence of grain boundaries. Despite previous work on MgO grain boundaries (e.g. Verma & Karki 2010; Hirel et al. 2019), little is yet known about the properties and mobility of ferropericlase grain boundaries at pressure conditions of deep planetary interiors.

            In this study, we carried out atomistic simulations based on the density functional theory to model the structures, energies and spin states of iron of a series of [001] symmetrical tilt grain boundaries in ferropericlase as a function of pressure. Based on these results, we investigated the mechanical behavior of the Σ5 tilt grain boundary by applying simple shear increments to the simulation cell to trigger grain boundary migration. Here, we will present the different mechanisms of grain boundary migration and the evolution of the ideal shear strengths up to a pressure of 400 GPa. Our results show that the mechanical strength of the grain boundaries and the directionality of their motion strongly varies with increasing pressure. Especially at pressure conditions of super-Earth exoplanets, significant grain boundary weakening is observed with increasing depth.  Implications for the deformation of ferropericlase at conditions of Earth’s and super-Earth’s mantles will be finally discussed.

How to cite: Ritterbex, S. and Tsuchiya, T.: Ab initio investigation of the intercrystalline mechanical behavior of ferropericlase at extreme pressures of planetary mantles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1140, https://doi.org/10.5194/egusphere-egu22-1140, 2022.

In the early solar system radiogenic heating by ²⁶Al and collisions are the two prominent ways expected to modify the internal composition of icy planetesimals, building blocks of comets, by removing highly volatile compounds like CO, CO₂ and NH₃. However, observations indicate that even large comets like Hale-Bopp (R ≈ 35 km) can be rich in these highly volatile compounds [1].
Here we constrain under which conditions icy planetesimals experiencing both internal heating and collisions can retain pristine interiors [2]. For this purpose, we employ both the state-of-the-art finite difference marker-in-cell code I2ELVIS [3] to model the thermal evolution in 2D infinite cylinder geometry and a 3D SPH code [4] to study the interior heating caused by collisions among icy planetesimals. For simplicity we assume circular porous icy planetesimals with a low density (≈ 470 kg/m³) based on measurements for comet 67P/Churyumov-Gerasimenko [5].
For the parameter study of the thermal history we vary (i) icy planetesimal radii, (ii) formation time and the (iii) the silicate/ice ratio. For the latter we keep the mean density fixed and change the porosity of the icy planetesimal. For the impact models we use porous, low-strength objects and vary (i) target and (ii) projectile radii, (iii) impact velocity as well as (iv) impact angle. Potential losses of volatile compounds from their interiors are calculated based on their critical temperatures taken from literature [6]. Our combined results indicate that only small or late-formed icy planetesimals remain mostly pristine, while early formed objects can even reach temperatures high enough to melt the water ice.

REFERENCES
[1] Morbidelli & Nesvorný, In: The Trans-Neptunian Solar System. 25–59 (2019). [2] Golabek & Jutzi, Icarus 363, 114437 (2021). [3] Gerya & Yuen, Phys. Earth Planet. Int. 163, 83-105 (2007). [4] Jutzi, Planet. Space Sci. 107, 3–9 (2015). [5] Sierks et al., Science 347, 1044 (2015). [6] Davidsson et al., Astron. Astrophys. 592, A63 (2016).

How to cite: Golabek, G. and Jutzi, M.: Modification of icy planetesimal interiors by early thermal evolution and collisions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1433, https://doi.org/10.5194/egusphere-egu22-1433, 2022.

According to the canonical model, the Moon was formed in the aftermath of a giant impact, when the proto-Earth was struck by a Mars-size impactor leading to a debris disk from which the Moon accreted. This event is thought to have been sufficiently energetic to cause wholesale melting of the Moon. Solidification of the resulting Lunar Magma Ocean (LMO) involves plagioclase flotation and formation of an anorthositic crust that blankets the residual LMO. This crust may form directly through plagioclase flotation or involve more complex reprocessing mechanisms. Extensive fractional crystallization of the LMO likely led to formation of a residual KREEP component in the crust, enriched in K, REE, P and other incompatible elements relative to the bulk Moon, whose signature has been recognized in several lunar samples (e.g.  feldspathic basalt).

The experimentally-constrained liquid lines of descent of a range of plausible LMO compositions bear strong resemblances to one another, crystallizing in the sequence olivine -> opx -> cpx + plagioclase -> quartz + Fe-Ti oxide. Crystallisation of olivine ± orthopyroxene prevails, depending on the composition, between 61-77 PCS (percent solidified), followed by the concomitant appearance of plagioclase + cpx at 1230±30 ^oC. Crystallisation of plagioclase marks the point at which the crystallisation sequences diverge owing to differences in bulk composition (e.g. refractory element content), which in turn influence phase saturation. Existing experiments on liquid lines of descent lack resolution, in particular at the point of quartz and Fe-Ti oxide saturation. Moreover, these experiments rarely proceed to the extent required to produce a KREEP component. In this work, we aim to more precisely determine the phase relations during crystallisation of the uppermost LMO, and assess possible mechanisms of formation of the KREEP component.

An isobaric series (8 - 5kbar) of six experiments on the bulk silicate Moon composition of O’Neill (1991) yields a crystallization sequence beginning at 1250 ^oC with olivine ± opx ± Cr-sp (69 PCS), followed by plagioclase and clinopyroxene at 1200 ^oC (77 PCS). Our mineral and melt major and trace-element abundances constrain the terminal stages of LMO crystallisation. Melt compositions remain near 45 wt% SiO₂ during the final crystallization stage while FeO increases from 12 wt% (bulk) to 20 wt% at plagioclase saturation. The Al₂O₃ and CaO budget is controlled by plagioclase crystallization (but not cpx) as the An# is as high as 97. We report mineral/melt partitioning coefficients for La, Ce, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Y, Zr, Th and U for plagioclase, pigeonite and high-Ca clinopyroxene and use the lattice strain model to evaluate these, also in the context of literature data. These partition coefficients are therefore the most suitable for understanding the origin of the KREEP component.  

Preliminary results suggest KREEP forms only after 99 PCS due to the evolved melt and the relatively rapid cooling rate of the surface magma ocean once crystal fraction is high. The last stage of eutectic crystallisation should lead to gabbroic rocks as the final crystallisation product.  

How to cite: Ofierska, W., Schmidt, M., Sossi, P., and Liebske, C.: Crystallisation of the upper lunar magma ocean and implications for KREEP and crust formation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1746, https://doi.org/10.5194/egusphere-egu22-1746, 2022.

Planetary differentiation in small bodies is believed to be ruled by several partial end-states that were dominated by low degrees of partial melting and melt segregation, before arriving at the formation of rocky planets. Having a better understanding of non-equilibrium melting processes in undifferentiated chondritic materials is critical to characterize planetary differentiation processes and the formation of rocky planets and differentiated asteroids. In this context, partial melting experiments of natural chondrites can provide unique insights into the petrological evolution associated with early planetary differentiation of planetesimals. For this study, we performed partial melting experiments using fragments from the ordinary chondrite DAV01001. Experiments were performed in a piston-cylinder at 1 GPa pressure, at temperatures from 1100 to 1300 °C and for 24 hours run duration. Reducing conditions were imposed by the use of graphite capsules. The experimental products were analysed using electron microprobe and synchrotron radiation computed microtomography (SR-µCT).

DAV01001 is an equilibrated L6 ordinary chondrite that has still visible relic chondrules and contains olivine (Fo₇₅), low-Ca pyroxene (En₇₇Fs₂₁Wo₂), high-Ca pyroxene (En₄₇Fs₈Wo₄₅), albitic plagioclase (An₁₃Ab₈₁Or₆), metal, troilite, chromite, and apatite. Upon heating, metal and troilite disappear at 1100 °C forming two immiscible phases, one made of pure metal with variable amounts of Ni, the other made of a metal-sulphide liquid of variable composition. Chromite starts melting at 1100 °C and disappears at 1300 °C. Silicatic melt forms already at 1100 °C as a result of the melting of plagioclase. With increasing temperature, the pyroxene and olivine begin to melt and shift the composition of the liquid towards trachy-andesitic (1200 °C) and basaltic trachy-andesitic to andesitic (1300 °C) compositions. Melting of olivine and pyroxene is accompanied by the crystallisation of both phases. The newly-formed olivine has a composition varying from Fo₈₀ to Fo₅₉, becoming progressively enriched in Fe and Ca and depleted in Ni at increasing temperature. The newly-formed pyroxene has a variable Ca content, and is enriched in Al and Cr and depleted in Fe and Mn. The new-grown olivine and pyroxene crystals have a strong affinity with chondritic/primitive achondrites compositions, in contrast to the melts that have a good affinity to a bulk HED composition. Overall, the combination of melting and crystallisation fixes the amount of silicatic liquid to a rather constant value of 10% vol.

SR-µCT was used to create 3D reconstructions of the experimental samples, in order to evaluate the efficiency of metal segregation at increasing degrees of partial melting. At increasing temperature, no change in the object density (number of 3D particles divided by the sample volume) is observed but only a progressive increase of the roundness and sphericity of the particles. This suggests that, even in presence of an interconnected liquid silicate phase (~10% vol), the coalescence of the metal phases does not occur spontaneously and other forces such as rotational spin or deformation are needed to segregate metal under these conditions.

How to cite: Iannini Lelarge, S., Masotta, M., Folco, L., Mancini, L., and Pittarello, L.: Non-equilibrium melting of partially differentiated asteroids: insights from partial melting experiments on L6 chondrite DAV01001, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3089, https://doi.org/10.5194/egusphere-egu22-3089, 2022.

• The Apollo lunar samples reveal that Earth and the Moon have strikingly similar isotopic ratios, suggesting that these bodies may share the same source materials. This leads to the "standard" giant impact hypothesis, suggesting the Moon formed from a partially vaporized disk that was generated by an impact between the proto-Earth and a Mars-sized impactor. This disk would have had high temperature (~ 4000 K) and vapor mass fraction of ~20 wt %. However, impact simulations indicate that this model does not mix the two bodies well, making it challenging to explain the isotopic similarity. In contrast, more energetic impacts, such as a collision between two half Earth-sized objects, could mix the two bodies well, naturally solving the problem. These impacts would produce much higher disk temperatures (6000-7000K) and higher vapor mass fractions (~80-90 wt%). These energetic models, however, may have a challenge during the Moon accretion phase. Our analyses suggest that km-sized moonlets, which are building blocks of the Moon, would experience strong gas drag from the vapor portion of the disk and fall onto Earth on a very short timescale. This problem could be avoided if large moonlets (>1000 km) form very quickly by the process called streaming instability, which is a large clump formation mechanism due to spontaneous concentration of dust particles followed by gravitational collapse. We investigate this possibility by conducting numerical simulations with the code called Athena. Our 2D and 3D hydrodynamic simulations show that moonlet formation by streaming instability is possible in the Moon-forming disk, but their maximum size is approximately 50 km, which is not large enough to avoid the strong gas drag. This result supports the Moon formation models that produce vapor-poor disks, such as the standard model. We will further discuss implications for moons in the solar system and extrasolar systems (exomoons). 

How to cite: Nakajima, M., Atkins, J., Simon, J. B., and Quillen, A. C.: Moon Formation via Streaming Instability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3311, https://doi.org/10.5194/egusphere-egu22-3311, 2022.

During the differentiation of terrestrial planets, the metal phase from the impactor core segregates from the silicate phase of the magma ocean. This buoyant mass forms a turbulent thermal and settles toward the proto-core. During this descent, thermal and chemical exchange occurs at the boundary between the metallic and silicate phases. Based on laboratory fluid dynamic experiments mimicking the settling of the metallic thermal turbulent, we develop a Lagrangian approach of the mixing from the experimental velocity field. We are able to track the evolution of the material elongated as lamellae by the turbulent stirring. We have characterised the elongation rate, the aggregation of lamellae, and the probability density function of the elongation and concentration, which are not accessible from direct measurements in the experiments. We have also investigated the effect of the Reynolds number and density ratio on these quantities. These results will allow us to develop a new predictive model of the mixing and chemical transfer in thermal turbulent to better understand the equilibrium between metals and silicates during the accretion of terrestrial planets.

How to cite: Huguet, L. and Deguen, R.: Lagrangian approach of the mixing in a turbulent thermal, and implications for metal-silicate equilibrium during Earth's formation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3776, https://doi.org/10.5194/egusphere-egu22-3776, 2022.

Accurate measurements of a planet's mass, radius and age (provided for example by the PLATO mission and follow-up measurements) together with compositional constraints from the stellar spectrum can help us to deduce potential evolutionary pathways that rocky planets can evolve along, and allow us to predict the range of likely atmospheric properties that can then be compared to observations.

However, for the evolution of composition and mass of an atmosphere, a large degeneracy exists due to several planetary and exterior factors and processes, making it very difficult to link the interior (and hence outgassing processes) of a planet to its atmosphere. The community therefore thrives now to identify the key factors that impact an atmosphere, and that may lead to distinguishable traces in planetary, secondary outgassed atmospheres. Such key factors are for example the planetary mass (impacting atmospheric erosion processes) or surface temperature (impacting atmospheric chemistry, weathering and interior-atmosphere interactions).

Here we investigate the signature that a planet evolving into plate tectonics leaves in its atmophere due to its impact on volcanic outgassing fluxes and volatile releases to the atmosphere - leading possibly to distinguishable sets of atmospheric compositions for stagnant-lid planets and plate tectonics planets. These preliminary findings will need to be further investigated with coupled atmosphere-interior models including various feedback mechanisms such as condensation and weathering as well as atmospheric escape to space.

How to cite: Noack, L. and Brachmann, C.: Is planetary resurfacing a key factor for outgassing and gas speciation on rocky planets?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4128, https://doi.org/10.5194/egusphere-egu22-4128, 2022.

Both the Moon¹ and Mars² are known to have significant degree-1 variations in their crustal thicknesses, with the Moon's far side and Mars's southern hemisphere having far thicker crusts than their respective opposing hemispheres. A number of potential mechanisms have been proposed to explain these dichotomies, including large impacts in both cases^3,4, radiant heat from the Earth⁵ (in the case of the Moon), and large-scale volcanism⁶ (in the case of Mars). However, the effectiveness of these mechanisms are limited by the difficulty of sustaining a large hemispheric difference during the tens to hundreds of Ma of crustal formation. Both planets' lithospheres are examples of a fluid-dynamical boundary layer known as a stagnant lid, caused by temperature-dependent viscosity in a convecting system. We consider the effect of pressure on the viscosity of magma oceans and mantles, finding that under certain circumstances a spherically-symmetric stagnant lid is linearly unstable to asymmetric perturbations. The fastest-growing wavenumbers of this instability is degree 1, meaning that a small initial asymmetry may grow into a full-scale hemispherical dichotomy. We then numerically examine the stability of these asymmetric states, finding that they may last for hundreds of Ma. We also compare to the case of Mercury, a similarly-sized planet with no such crustal dichotomy, to determine if our analysis matches observations.

¹ Wieczorek, M.A., Jolliff, B.L., Khan, A., Pritchard, M.E., Weiss, B.P., Williams, J.G., Hood, L.L., Righter, K., Neal, C.R., Shearer, C.K., McCallum, I.S., Tompkins, S., Hawke, B.R., Peterson, C., Gillis, J.J. & Bussey, B. 2006 The Constitution and Structure of the Lunar Interior. Reviews in Mineralogy and Geochemistry 60, 221–364.

² Thiriet, M., Michaut, C., Breuer, D. & Plesa, A.-C. 2018 Hemispheric dichotomy in lithosphere thickness on mars caused by differences in crustal structure and composition. Journal of Geophysical Research: Planets 123 (4), 823–848.
Weiss, Benjamin P. & Tikoo, Sonia M. 2014 The lunar dynamo. Science 346 (6214), 1198

³ Garrick-Bethell, I., Perera, V., Nimmo, F. & Zuber, M.T. 2014 The tidal-rotational shape of the Moon and evidence for polar wander. Nature 512 (7513), 181–184.

⁴ Andrews-Hanna, J.C., Zuber, M.T. & Banerdt, W.B. 2008 The borealis basin and the origin of the martian crustal dichotomy. Nature 453 (7199), 1212–1215.

⁵ Roy, A., Wright, J.T. & Sigurðsson, S. 2014 Earthshine on a young moon: Explaining the lunar farside highlands. The Astrophysical Journal Letters 788 (2), L42.

⁶ Golabek, G.J., Keller, T., Gerya, T.V., Zhu, G., Tackley, P.J. & Connolly, J.A.D. 2011 Origin of the martian dichotomy and tharsis from a giant impact causing massive magmatism. Icarus 215 (1), 346–357.

How to cite: Watson, C., Neufeld, J., and Michaut, C.: Asymmetric growth of planetary stagnant lids, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4758, https://doi.org/10.5194/egusphere-egu22-4758, 2022.

The application of the short-lived radiogenic ¹⁸²Hf/¹⁸²W-system (t_1/2 = 8.9 Ma [1]) is a good approach to study early differentiation processes or potential involvement of long-term isolated and/or core-influenced mantle domains as components for ocean island basalts (OIB) [2,3].

Several examples of OIB worldwide (e.g., Hawaii, Samoa and Iceland) exhibit a negative He-W correlation [2], possibly connected to the incorporation of primordial material characterized by high ³He/⁴He ratios and negative µ¹⁸²W (¹⁸²W/¹⁸⁴W deviation of a sample from laboratory standards in parts per million). Anomalous W isotope compositions in combination with elevated ³He/⁴He ratios have previously been connected to seismically anomalous structures in the lowermost mantle, so-called “(mega) ultra-low velocity zones” [3]. Recently, such a structure was discovered beneath the Marquesas Archipelago [4]. This volcanic island chain is located in the South Pacific, in proximity of the Marquesas Fraction Zone. Its formation process is not yet fully understood. Based on high ³He/⁴He ratios in combination with other geochemical characteristics, such as Sr, Nd and Pb isotopes, a deep-lying mantle source has been suggested [5].

In this study, we have analysed seven samples from two islands of the Marquesas Archipelago, which exhibit ³He/⁴He ratios up to 14.4 Ra [5]. µ¹⁸²W ranges from -3.6 ±3.1 to 4.7 ±8.5. Hence, despite elevated ³He/⁴He in some of the samples, none of them display resolved negative ¹⁸²W anomalies and thus, no negative He-W correlation is observed. Interpretations for the decoupling of He-W systematics in samples from the Marquesas Archipelago will be discussed.

References:

[1] Vockenhuber et al., 2004, Phys. Rev. Lett.

[2] Mundl et al., 2017, Science

[3] Mundl-Petermeier et al., 2020, Geochim. Cosmochim. Acta

[4] Kim et al., 2020, Science

[5] Castillo et al., 2007, Chem. Geol.

How to cite: Herret, M.-T., Mundl-Petermeier, A., Castillo, P., and Kim, D.: Tungsten isotope implications for the source of ocean island basalts from the Marquesas Archipelago, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4890, https://doi.org/10.5194/egusphere-egu22-4890, 2022.

The position of the critical point determines the top of the liquid-vapor coexistence dome, and is a physical parameter of fundamental importance in the study of high-energy shocks, including those associated with large planetary impacts. For most major planetary materials, like oxides and silicates, the estimated position of the critical point is below 1 g/cm³ at temperatures above 5000 K. Here we compute the position of the critical point of one of the most ubiquitous materials: MgO. For this, we perform first-principles molecular dynamics simulations. We find the critical density to be in the 0.4 - 0.6 g/cm³ range and the critical temperature in the 6500 - 7000 K range. We investigate in detail the behavior of MgO in the subcritical and supercritical regimes and provide insight into the structure and chemical speciation. We see a change in Mg-O speciation towards lower degrees of coordination as the temperature is increased from 4000 K to 10000 K. This change in speciation is less pronounced at higher densities. We observe the liquid-gas separation in nucleating nano-bubbles at densities below the liquid spinodal. The majority of the chemical species forming the incipient gas-phase consist of isolated Mg and O atoms and some MgO and O₂ molecules. We find that the ionization state of the atoms in the liquid phase is close to the nominal charge, but it almost vanishes close to the liquid-gas boundary and in the gas phase, which is consequently largely atomic.

This research was supported by the European Research Council under EU Horizon 2020 research and innovation program (grant agreement 681818–IMPACT to RC). This research was performed by access to supercomputing facilities via eDARI stl2816 grants, PRACE RA4947 grant, Uninet2 NN9697K grant.

How to cite: Bögels, T. and Caracas, R.: The critical point and the supercritical regime of MgO, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5002, https://doi.org/10.5194/egusphere-egu22-5002, 2022.

How volatiles were incorporated in the building blocks of planets and small bodies in the protosolar nebula remains an outstanding question. Some scenarios invoke the formation of planetesimals from a mixture of refractory material and amorphous ice in the outer nebula while others argue that volatiles have been incorporated in clathrate or pure condensate forms in these solids. Here we study the fate of volatiles (H₂O, CO, CO₂, CH₄, H₂S, N₂, NH₃, Ar, Kr, Xe, and PH₃) initially delivered in the forms of amorphous ice or pure condensates to the protosolar nebula. We investigate the radial distribution of these volatiles via a transport module coupled with an accretion disk model. In this model, multiple icelines are considered, including the condensation fronts of pure condensates, as well as those of clathrates when enough crystalline water is available at given time and location. Our simulations show that a significant fraction of volatiles can be trapped in clathrates only if they have been initially delivered in pure condensate forms to the disk. Under specific circumstances, volatiles can be essentially trapped in clathrates but, in many cases, the clathrate of a given species coexists with its pure condensate form. Those findings have implications for the compositions of giant planets and comets.

How to cite: Schneeberger, A., Mousis, O., Aguichine, A., and Lunine, J.: Evolution of the reservoir of volatiles in the protosolar nebula, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5270, https://doi.org/10.5194/egusphere-egu22-5270, 2022.

The radiogenic elements K, Th, and U are large contributors to the heating inside a terrestrial planet. Because they act incompatible in solid mantle rocks, they prefer to gather in partial melt, which is generally less dense than the surrounding material and rises upwards. While rising, the melt transports the radiogenic heat sources and other incompatible elements towards the surface, where over time they accumulate inside the crust. The amount of the transported incompatible elements is heavily dependent on their degree of incompatibility in mantle rocks and therefore their mineral/melt partition coefficients. Despite the fact that partition coefficients can change by multiple orders of magnitudes from 0-15 GPa along a peridotite solidus (Schmidt and Noack, 2021), they were generally taken as constant in mantle evolution models due to a lack of high-pressure models and experimental data.

Based on the thermodynamic approach of Blundy et al. (1995), Schmidt and Noack (2021) modelled partition coefficients for sodium in clinopyroxene/melt from 0-15 GPa. As sodium has a very low strain in the M2 lattice site of clinopyroxene and is therefore very compatible, its partition coefficients can act as a reference to model the other elements from. In this study, we take the approach of Schmidt and Noack (2021) to model the partition coefficients of the above-mentioned heat producing elements and volatiles at local P-T conditions for partial melting events inside the mantle of terrestrial planets. We insert local bulk partition coefficients for an adequate mantle rock composition into a 1D interior evolution model of Mars. By comparing the results of the redistribution to models with constant partition coefficients, we can assess the impact of the locally calculated partition coefficients on the accuracy of models which deal with the thermal evolution of a planet and the enrichment of heat producing elements and volatiles inside the crust.

Blundy, J. et al. (1995): Sodium partitioning between clinopyroxene and silicate melts, J. Geophys. Res., 100, 15501-15515.

Schmidt, J.M. and Noack, L. (2021): Clinopyroxene/Melt Partitioning: Models for Higher Upper Mantle Pressures Applied to Sodium and Potassium, SysMea, vol 13 nr 3&4, to be published.

How to cite: Schmidt, J. M. and Noack, L.: Applying locally calculated partition coefficients for radiogenic heat sources and volatiles to interior evolution models of terrestrial planets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5850, https://doi.org/10.5194/egusphere-egu22-5850, 2022.

Every planet is singular, with scars and bumps at their surface. One planet, one history. But the physics at play is common to them, connecting planetary bodies together. Tectonics is a common theme of what we can observe on planets of the solar system, and a central question for explanets. More than 20 years of geodynamic modelling has resulted in  identifying a diversity of tectonic regimes for mantle convection, from very active, like heat-pipe (Monnereau and Dubuffet, 2002 among others) and squishy lid (Lourenço et al., 2020) to almost inert, like stagnant lid (Schmeling and Jacoby, 1982). Tectonics is an emergent property deriving from the intimate structure and composition of a planet. It is also a fundamental piece shaping the surface environment. This presentation will attempt to give an overview of tectonic regimes of planets and propose typical evolutional scenari, connecting structural and compositional histories from the depth to the surface.

References

Lourenço, D. L., Rozel, A. B., Ballmer, M. D., & Tackley, P. J. (2020). Plutonic‐squishy lid: A new global tectonic regime generated by intrusive magmatism on earth‐like planets. Geochemistry, Geophysics, Geosystems, 21, e2019GC008756.

Monnereau, M., & Dubuffet, F. (2002). Is Io's mantle really molten?. Icarus, 158, 450-459.

Schmeling, H., & Jacoby, W. R. (1982). On modelling the lithosphere in mantle convection with non-linear rheology. Journal of Geophysics, 50, 89-100.

How to cite: Coltice, N.: An overview of modeled dynamic histories of rocky planets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6028, https://doi.org/10.5194/egusphere-egu22-6028, 2022.

Introduction: Hydrogen isotopic compositions (D/H or 𝛿D) in chondrites are a powerful tool for deciphering the source of water delivered to terrestrial planets (1). CM-type carbonaceous chondrites contain up to ~10wt.% H₂O, retained as OH in phyllosilicates. The D/H ratio of phyllosilicates (a direct proxy for water) in chondrites cannot be determined directly using whole rock measurements, because their matrices also accreted D-rich organics which are mixed with D-poor phyllosilicates at the sub-micrometer scale. To address this issue, water D/H has been estimated by in-situ measurements of both D/H and C/H in hydrated chondrites, which define a mixing line in a D/H vs. C/H plot. The intercept gives the isotopic composition of the phyllosilicate alone (1). However, SIMS measurements of water D/H using this method can be compromised by (i) contamination and (ii) limited dispersion of the phyllosilicates/organics ratio measured with a large primary beam.

Methods: We addressed both issues using the Wash U NanoSIMS50 which allows us to obtain coordinated isotopic and elemental data with high-spatial resolution. H⁻,D⁻ with ¹²C⁻,¹²C¹⁴N⁻,¹²C¹⁵N⁻,²⁸Si⁻ are collected using magnetic-field peak-jumping in “Combined Analysis” mode. Centering of the secondary ions beam in Cy and P2/P3 planes of the secondary column changes between the low and high masses, resulting in misaligned ion images. So, we used AutoHotkey scripts to send a different Cy voltage for every B-field set up through the virtual keyboard of the NanoSIMS. To separate phyllosilicate-rich from organic-rich pixels, we assume that D/H is not simply a linear function of C/H, but in general D/H is approximated by a function using all measured species: . The true phyllosilicate composition [C,N,Si,H] is estimated from the data and is then used to estimate the water D/H composition from the linear regression model. NanoSIMS isotopic analyses were carried out in a matrix area of the CM Maribo and our analytical conditions were the same as outlined in (2).

Results: First, we calculated a 𝛿D value of −178±46‰ (2σ) for the phyllosilicates in Maribo using the D/H vs. C/H correlation from the resized pixels. This value is higher than previous measurements using SIMS [𝛿D ≈ −420 to −270‰, (2, 3)], demonstrating that D/H ratio of phyllosilicate cannot be simply determined using the D/H vs. C/H line in this matrix area. Second, we calculated the 𝛿D value of the phyllosilicates in Maribo using all the measured species and the linear regression model described above. We found that the phyllosilicate D/H is best correlated for dominant contributions of N, Si and H (b=0.14, c=0.58 and d=−0.86) and minor contributions of C (a=0.06). We calculated a 𝛿D value of −286+/-60‰. This value is consistent with those previously determined by SIMS, demonstrating that our method can be used to precisely determine the water D/H on very small areas.

(1) Alexander C.M.O’D. et al. (2012) Science, 337, 721–723.

(2) Vacher L.G. and Ogliore R.C. (2022) 53rd LPSC, 2653.

(3) van Kooten E.M.M.E. et al. (2018) GCA, 237, 79–102.

(4) Piani L. et al. (2021) EPSL, 567, 117008.

How to cite: Vacher, L. G. and Ogliore, R. C.: Determination of Water D/H in Hydrated Chondrites using NanoSIMS Imaging, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6584, https://doi.org/10.5194/egusphere-egu22-6584, 2022.

The Martian dichotomy features a ~25 km difference in crustal thickness and ~5 km contrast in topography between the southern highlands and northern lowlands [1]. Among various origin hypothesis, a southern impact [2,3] creates a magma pond which, upon cooling, induces crustal thickening and thereby forms the crustal dichotomy within 10s of million years.

Our previous study [4], which utilizes a head-on parametrized impact in 2D geometry, shows that an impact-induced magma pond in the southern hemisphere is able to not only create a thickened crust in the south, but also a satisfying volcanic history with localized melt production in the equatorial region at geologically recent time.  Depleted material, formed from crystallization of the magma pond, spreads and underplates the thicker and colder Northern lithosphere undisturbed by the impact, reinforcing the lesser extent of volcanism in the northern hemisphere. Our resultant mantle structure is consistent with existing simulation efforts that focus on the post-dichotomy formation evolution history [5], and in addition gives the context of how such thermochemical structure is developed.

In order to include a more realistic impact scenario, we use smoothed particle hydrodynamics (SPH) simulations [6] to model the first 24-36 hours of a giant impact between proto-Mars and its impactor. The SPH result is then transferred to the mantle convection code StagYY [7], as an initial thermal condition, to simulate the long-term evolution of the crust and mantle for the subsequent 4.5 billion years. We systematically vary the impactor size, impact velocity and pre-impact Martian mantle temperature. Our preliminary results show that a 45-degree impact does not form a Martian dichotomy-like crustal structure, while a 15-degree impact is a better match.  With a realistic impact, the mechanisms reported in our parametrized impact study still hold.

References:

[1] Watters, T., McGovern, P., & Irwin III, R. (2007). Hemispheres Apart: The Crustal Dichotomy on Mars. Annual Review Of Earth And Planetary Sciences, 35(1), 621-652.

[2] Reese, C., Orth, C., & Solomatov, V. (2011). Impact megadomes and the origin of the martian crustal dichotomy. Icarus, 213(2), 433-442.

[3] Golabek, G., Keller, T., Gerya, T., Zhu, G., Tackley, P., & Connolly, J. (2011). Origin of the martian dichotomy and Tharsis from a giant impact causing massive magmatism. Icarus, 215(1), 346-357.

[4] Cheng, K.W., Tackley, P.J., Rozel, A.B., Golabek, G.J. (2021). Martian Dichotomy: Impact-induced Crustal Production in Mantle Convection Models, Abstract [DI35B-0023] presented at 2021 Fall Meeting, AGU, New Orleans, LA, 13-17 Dec.

[5] Plesa, A., Padovan, S., Tosi, N., Breuer, D., Grott, M., & Wieczorek, M. et al. (2018). The Thermal State and Interior Structure of Mars. Geophysical Research Letters, 45(22), 12,198-12,209.

[6] Emsenhuber, A., Jutzi, M., Benz, W. (2018). SPH calculations of Mars-scale collisions: The role of the equation of state, material rheologies, and numerical effects. Icarus, 301, 247-257

[7] Tackley, P. (2008). Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid. Physics Of The Earth And Planetary Interiors, 171(1-4), 7-18.

How to cite: Cheng, K. W., Rozel, A., Ballantyne, H., Jutzi, M., Golabek, G., and Tackley, P.: Forming the Martian dichotomy with realistic impact scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6591, https://doi.org/10.5194/egusphere-egu22-6591, 2022.

      The crystallization of the Basal Magma Ocean (BMO) sets the stage for the long-term evolution of terrestrial planets and may leave behind large-scale thermochemical structures in the lower mantle. Previous work shows that a FeO-enriched molten layer or basal magma ocean (BMO) is stabilized at the core-mantle boundary of large rocky planets such as Earth for a few billion years. The BMO itself is expected to freeze by fractional crystallization (FC) because it cools very slowly. However, the fate of BMO cumulates has not yet been systemically explored.

To explore the fate of the BMO cumulates in the convecting mantle, we explore 2D geodynamic models with a moving-boundary approach. Flow in the mantle is explicitly solved, but the thermal evolution and related crystallization of the successively crystallizing BMO (i.e., below the moving boundary) are fully parameterized. The composition of the crystallizing cumulates is self-consistently calculated in the FeO-MgO-SiO₂ ternary system according to Boukaré et al. (2015). In some cases, we also consider the effects of Al₂O₃ on the cumulate density profile. We then investigate the entrainment and mixing of BMO cumulates by solid-state mantle convection over billions of years as a function of BMO initial composition and volume, BMO crystallization timescales, distribution of internal heat sources, and mantle rheological parameters (Rayleigh Number and activation energy). We vary the initial composition of BMO by manipulating the bulk molar fraction of FeO, MgO, and SiO₂, e.g. considering BMO compositions such as pyrolite, lower-mantle partial melts of pyrolite (after 50% batch crystallization), or Archean Basalt.

For all our model cases, we find that most of the cumulates (first ~90% by mass) are efficiently entrained and mixed through the mantle. However, the final ~9% of the cumulates are too dense to be entrained (either fully or partially) over the age of the Earth, and rather remain at the base of the mantle as a strongly FeO-enriched solid layer. Unless the initial thickness of the BMO is ≤100 km, this strongly enriched and intrinsically dense layer should cover the CMB globally. We highlight that this outcome of BMO fractional crystallization is inconsistent with the geophysical constraints. Our results suggest that the BMO was either very small initially or did not crystallize by end-member FC. An alternative mode of crystallization may be driven by an efficient reaction between a highly-enriched last-stage BMO with the overlying mantle. Such reactive crystallization may be much faster than FC of the BMO, as it is driven by chemical disequilibrium instead of (slow) planetary cooling.

How to cite: Ismail, M. and Ballmer, M.: Fractional Crystallization Of The Basal Magma Ocean: Consequences For Present-day Mantle Structure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6651, https://doi.org/10.5194/egusphere-egu22-6651, 2022.

The formation mechanism of Jupiter is still uncertain, as multiple volatile accretion scenarios can reproduce its metallicity [1-4]. The Galileo mission allowed in situ measurements of the abundances of several elements (Ar, Kr, Xe, C, N, S and P), which exhibit a uniform enrichment of 2 to 5 times the protosolar abundance, and a subsolar abundance has been measured for O. Recent measurements for N and O by the Juno mission confirmed the supersolar abundance of N, but indicated that the abundance of O may also be supersolar [5]. Elemental abundances measured in the Jupiter's atmosphere are key ingredients to trace the origin of various species.
Here, we investigate the possible timescale and location of Jupiter's formation using measurements of molecular and elemental abundances in its envelope. To do so, we use a 1D accretion disk model to compute the properties of the protosolar nebula (PSN) that includes radial transport of trace species, present in the form of refractory dust, a mixture of ices and their vapors, to compute the composition of the PSN [6]. We focus on the radial transport of volatile species by advection-diffusion combined with the effect of icelines, computed as sublimation/condensation rates. Initialy, the disk is uniformly filled with H₂O, PH₃, CO, CO₂, CH₄, CH₃OH, NH₃, N₂, H₂S, Ar, Kr and Xe [6,7], corresponding to the main bearers of C, N, O, P, S, Ar, Kr and Xe.
As the PSN evolves, solid particles drift inward due to gas drag. Volatile species are thus efficiently transported to their respective icelines, where they sublimate. This results in supersolar abundances of volatile elements in the inner part of the PSN. We find that the composition of Jupiter’s envelope can be achieved by accretion of enriched gas only, or a mixture of gas and solids, depending on the viscosity of the PSN. In both cases, the composition of the PSN matches the one measured in Jupiter’s envelope in timescale that are compatible with a formation by core accretion or gravitational collapse.

[1] Gautier, D., Hersant, F., Mousis, O., et al. 2001, ApJL, 550, L227.
[2] Mousis, O., Ronnet, T., and Lunine, J. I. 2019, ApJ, 875, 9.
[3] Öberg, K. I. and Wordsworth, R. 2019, AJ, 158, 194.
[4] Miguel, Y., Cridland, A., Ormel, C. W., et al. 2020, MNRAS, 491, 1998.
[5] Li, C., Ingersoll, A., Bolton, S., et al. 2020, Nature Astronomy, 4, 609.
[6] Aguichine, A., Mousis, O., Devouard, B., and Ronnet, T. 2020, ApJ, 901, 97.
[7] Lodders, K., Palme, H., & Gail, H.-P. 2009, Landolt Börnstein, 4B, 712

How to cite: Aguichine, A., Mousis, O., and Lunine, J.: Formation of Jupiter's envelope from supersolar gas in the protoplanetary disk, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6692, https://doi.org/10.5194/egusphere-egu22-6692, 2022.

How to cite: Spaargaren, R., Ballmer, M., Mojzsis, S., and Tackley, P.: The effects of terrestrial exoplanet bulk composition on long-term planetary evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7484, https://doi.org/10.5194/egusphere-egu22-7484, 2022.

The Moon deforms in response to tidal forcing exerted by the Earth, the Sun and, to a lesser extent, by other planetary bodies. Their observations from ground-based and space-borne instruments, as well as Lunar surface missions, provide one of the most significant constraints that can be employed to unravel the deep interior (Williams et al. [2014], Williams and Boggs [2015]). The tidal forcing generates periodic variations of the harmonic degree-2 shape and gravity that depend on the internal composition and structure of the Moon. These changes in shape and gravity of the Moon are described by three geodetic parameters, called Tidal Love numbers (TLNs). Because of their low degree, these TLNs are sensitive to the structure of the deep interior (e.g., Khan et al. [2004]). Apart from the geodetic constraints, the Moon and Mars (e.g. Zweifel et al. [2021]) are the only other bodies besides the Earth for which seismic data are available. Seismic studies using the Apollo Passive Seismic Experiment (PSE) constrain the seismic wave velocity distribution and therefore give a glimpse of the Moon’s interior structure (Garcia et al. [2011], Weber et al. [2011]). However, at greater depth, seismic data do not provide sufficient resolution on the velocity profile, leaving the near-centre Moon structure uncertain. Other studies based upon geophysical constraints (Khan et al. [2004], Harada et al. [2014, 2016], Matsumoto et al. [2015]) and the re-analysis of the Apollo seismic data suggested the existence of an attenuated region called low viscosity zone (LVZ) originated from a melting layer at the core-mantle boundary (Khan and Mosegaard [2001], Weber et al. [2011], Harada et al. [2014], Rambaux et al. [2014]).

Based on geodetic observations and seismic studies, we perform Monte Carlo simulations for combinations of thicknesses, densities and viscosities for two classes of Moon’s models, one including an undifferentiated core and one including an inner and outer core, with both classes assuming an LVZ at the core-mantle boundary. By comparing predicted and observed tidal deformation parameters we find that the existence of an inner core cannot be ruled out. Furthermore, by deducing temperature profiles for the LVZ and the mantle following Earth assumptions, we obtain stringent constraints on the radius, viscosity, and density of the LVZ. We also infer the first estimation for the outer core viscosity, for our two possible scenarios.

How to cite: Briaud, A., Fienga, A., Melini, D., Rambaux, N., Mémin, A., Spada, G., Saliby, C., Hussmann, H., and Stark, A.: Constraints on the Moon’s deep interior from tidal deformation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7919, https://doi.org/10.5194/egusphere-egu22-7919, 2022.

The long-term evolution of the mantle is simulated using 2D spherical annulus geometry to examine the effect of heterogeneous conductivity on the stability of primordial thermo-chemical reservoirs. Conductivity of the mantle is often emulated in numerical models using purely depth-dependent profiles (e.g., taking on values between 3 and 9 W/m-K). This approach is meant to synthesize the mean conductivities of mantle materials at their respective conditions in-situ. However, because conductivity depends also on temperature and composition, their role in the conductivity of the mantle is masked. This issue is significant because dynamically evolving temperature and composition introduce lateral variations in conductivity, especially in the deep-mantle. Minimum and maximum variations in conductivity are due to the temperatures of plumes and slabs, respectively, and depth-dependence directly controls the amplitude of the conductivity (and its variations) across the mantle depth. Our simulations allow assessing the consequences of these variations on mantle dynamics, in combination with the reduction of thermo-chemical pile conductivity with iron composition, which has so far not been well examined. 

First, we examine the effect of depth (D)-dependence employing a linear profile and vary the bottom-to-top conductivity ratio. We find that increased conductivity ratio acts to reduce pile temperature. Greater conductivity in the lower mantle helps to efficiently extract heat from piles (at rates sufficient to overcome or suppress temperature increases due to enrichment in HPEs). This reduction in thermal buoyancy stabilizes the piles and may play a major role in organizing thermo-chemical reservoirs into two distinct piles. 

Next, the combined effects of temperature (T) and composition (C) are examined. A positive feedback occurs when the reduced conductivity of piles inhibits its cooling and the resulting increase in temperature further reduces its conductivity. Consequently, the augmented thermal buoyancy destabilizes piles (i.e., greater topography or enhanced erosion). Furthermore, the combined T and C-dependences can greatly underestimate typical mantle conductivities if D-dependence is also underestimated. By increasing the amplitude of D-dependence, the destabilizing effects of T and C-dependence can be suppressed. 

Finally, mineral physics data is employed to emulate a more realistic depth-dependent profile for the upper and lower mantle. Depth-dependence is no longer a linear profile and values range from 3 to 27.5 W/m-K. Buoyancy ratio and the enrichment in heat-producing elements in piles are examined for this conductivity model to determine potential evolution scenarios of primordial thermo-chemical piles. We find that this model produces stable piles for periods exceeding the age of the Earth. When B is reduced from 0.23 to 0.15, piles are destabilized earlier (by approx 1 Gyr) for cases with lesser depth-dependence. HPE enrichment in piles increases their temperature over time (and further reduces their conductivity). For HPE enrichment 10 times the mantle heat production, two distinct piles are formed with moderate topography. For greater enrichment, the piles become unstable and material becomes entrained by thin plume conduits.

How to cite: Guerrero, J., Deschamps, F., Li, Y., Hsieh, W.-P., and Tackley, P.: The effect of heterogeneous conductivity on the long-term thermo-chemical evolution of the lower mantle: implications for primordial reservoirs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9006, https://doi.org/10.5194/egusphere-egu22-9006, 2022.

Super-Earth LHS 3844b is a rocky exoplanet with a radius around 1.3 Earth radii. Its thermal phase curve suggests that the dayside temperature is around 1040 K and the nightside temperature is around 0 - 700 K, indicating inefficient atmospheric heat circulation. Therefore, this planet most likely lacks an atmosphere. In a previous study, we have shown that such a strong surface temperature dichotomy can lead to a so-called hemispheric tectonic regime. In such a regime, a cold downwelling forms preferentially on one side and hot upwellings are getting pushed towards the other hemisphere. 
GJ 486b is a super-Earth that is very similar to LHS 3844b in terms of size and it is currently unknown whether this planet has an atmosphere. In this study, we are investigating under which circumstances hemispheric tectonics can operate on GJ 486b. We also investigate the stability of hemispheric tectonics. 

We run 2D geodynamic simulations of the interior mantle flow using the mantle convection code StagYY. The models are fully compressible with an Arrhenius-type viscosity law where the mantle is mostly composed of perovskite and post-perovskite. The lithospheric strength is modelled through a plastic yielding criteria and the heating mode is either basal heating only or mixed heating (basal and internal heating). 
We use general circulation models (GCMs) of potential atmospheres to constrain the surface temperature assuming different efficiencies of atmospheric heat circulation. 

We find that a hemispheric tectonic regime is also possible for surface temperature contrasts with moderate heat redistribution. The location of the strong downwelling depends on several factors such as the surface temperature contrast and strength of the lithosphere. By reducing the temperature contrast, the location of the downwelling becomes less stable and it can start to move from one side towards the other over very long timescales (Gyrs). Our results show that hemispheric tectonics could operate on tidally-locked super-Earths, even if the surface temperature contrast between the dayside and nightside is not as strong as for LHS 3844b. Upwellings that rise preferentially on one hemisphere could lead to generation of melt and subsequent outgassing of volatiles on that side. Imprints of such outgassing on the atmospheric composition could possibly be probed by current and future observations such as JWST, ARIEL or the ELT. 

How to cite: Meier, T. G., Bower, D. J., Lichtenberg, T., Hammond, M., and Tackley, P. J.: Exploring hemispheric tectonics on tidally-locked super-Earths, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9683, https://doi.org/10.5194/egusphere-egu22-9683, 2022.

A star and its planets are born from the same molecular cloud, so they share the same origin of the essential building blocks: elements. The compositional deviations between stars and (particularly rocky) planets are associated with the gas-dust fractionation process in the protoplanetary disk and subsequent formation processes of the planets. During these processes, a key differentiator between forming a gas giant (e.g. Jupiter) and a rocky planet (e.g. Earth) is devolatilisation – i.e. depletion of volatiles (e.g. H, C, and O) resulting in completely different bulk compositions between the two types of planets, with former being dominated by gases/ices and the latter by rocks. This devolatilisation mechanism has been empirically observed in both the Solar System and other planetary systems (e.g. in polluted white dwarf atmospheres), but has yet to be explored and implemented in the prevalent planet-formation models.

I will explore both the nebular and post-nebular devolatilization processes based on the first principals starting from the stellar nebulae to rocky planetary bodies. These processes will then be coupled with a state-of-the-art planet formation model. Such a coupled/hybrid devolatilisation-dynamics model will enable a detailed and accurate estimation of the volatile (subject to devolatilisation) and refractory (resistant to devolatilisation) contents of a small (rocky) planet, as well as the physical properties (e.g. mass, radius, and orbit) of the planet. These unprecedentedly detailed predictions of planetary elemental composition will provide crucial constraints, together with mass, radius and orbital properties, for further modelling of planetary interiors, surfaces, and atmospheres. Together, these will lead to a new level of predictive statistical understanding of the detailed properties of small (rocky) planets in our solar neighbourhood.

How to cite: Wang, H.: Devolatilisation during planet formation: A hybrid model of chemistry and dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10146, https://doi.org/10.5194/egusphere-egu22-10146, 2022.

Mercury’s high core mass ratio means that its core evolution could have strong implications for its mantle dynamics, surface geology, and the generation of a dynamo. Radial contraction, present-day magnetic field, ancient crustal magnetisation, and early extensive volcanism are some of the observations that are controlled by the thermal evolution of Mercury’s interior and therefore influenced by the core.

The low intensity and lack of small-scale variations in Mercury’s present-day magnetic field can be explained by a convective liquid below a thermally stratified core layer where heat is transported conductively. Numerical studies confirmed the plausibility of a sub-adiabatic heat flow at the core-mantle boundary, giving rise to the thermally stratified layer. Investigating the conditions leading to the formation of the thermally stratified layer, and its evolution, is of crucial importance for our understanding of Mercury’s geological and geophysical history.

We couple mantle and core thermal evolution to investigate the conditions under which the thermally stratified layer is formed in the liquid core, and to study the interactions between the core and the mantle. Events such as the cessation of convection in the mantle may strongly influence the core-mantle boundary heat flow and affect the thickness of the thermally stratified layer in the core. Our results highlight the importance of coupling mantle evolution with that of the core, taking into account processes such as melting in the mantle and solidification of an inner core, and the effects of a sub-adiabatic core-mantle boundary heat flow.

How to cite: Zhao, Y., Deproost, M.-H., Knibbe, J., Rivoldini, A., and Van Hoolst, T.: Evolution of the thermally stratified layer in the outer core of Mercury, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12336, https://doi.org/10.5194/egusphere-egu22-12336, 2022.

From the observations on ~1000 recognizable impact craters on Venus’ surface, the average surface age for Venus is comparable to the average surface age for Earth, and is significantly younger than the surface ages of other solar terrestrial planets. To explain Venus’ young surface without plate tectonics, the global tectonics of Venus have often been proposed to be in an episodic-lid regime with catastrophic global overturns. Previous episodic-lid geodynamic models often assume an olivine-diffusion-creep rheology for Venus’ crust, resulting in global overturns followed by stagnant-lid phases with near-zero surface mobilities. However, some tectonic units on Venus’ surfaces show substantial tectonic deformation, such as tesserae and coronae. Recent analyses of satellite images on Venus' surface also suggest possible widespread lithospheric mobilities in the lowland basins. And these observations can hardly be explained by the stagnant-lid phases between overturns in the episodic-lid models.

In this study, we test the influence of (1) a composite, experiment-based crustal rheology (including diffusion creep, dislocation creep, and plasticity), and (2) intrusive magmatism, on Venus’ surface tectonics, using the mantle convection code StagYY in a 2D spherical annulus geometry. Our results show that applying the experiment-based rheology and intrusive magmatism in the model results in (1) both global and regional overturns, (2) high and continuous surface mobilities that indicate substantial surface deformation between global overturns, and (3) a young and thinner crust that is consistent with current estimations.  As for volcanic activities, contrary to olivine-diffusion-creep models, there is no persistent mantle plume in our models when the realistic crustal rheology is applied. The basalt cumulated between the upper and lower mantle affects convective flows in the mantle and mantle upwellings from the core-mantle boundary. Also, there are short-term, randomly located volcanisms within crust between global overturns, which are consistent with recent observations of active magmatism on Venus’ surface and the short-term plumes suggested by coronae formation models. The surface tectonics in our models are dependent on the heat transfer efficiency in the upper mantle. And the tectonic regime is different from both episodic-lid regime and plutonic-squishy-lid regime that are proposed in previous literature, and can provide insights on the tectonic style for Venus and early Earth.

How to cite: Tian, J., Tackley, P., and Rozel, A.: Implications of a realistic crustal rheology and intrusive magmatism on Venusian tectonics: a geodynamic perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12407, https://doi.org/10.5194/egusphere-egu22-12407, 2022.

Rifting and rises are prominent landscape features in the roughly triangular area characterized by the presence of three major rises (Atla, Beta and Themis) and two corona-dominated long chasmata (Hecate and Parga). The coronae population associated with these chasmata represents 35% of all Venusian coronae and 56% of coronae associated with fracture zones (Smrekar et al., 2010). We focused on the spatial analysis of the coronae population associated with Parga chasma for identifying the depth of the main thermal anomaly that fed (and maybe still feeds) them.

We explore a formation mechanism for coronae based on the Rayleigh–Taylor (R-T) gravitational instability (Tackley and Stevenson, 1991) of the lithosphere that may occur when a layer of dense fluid overlies a layer of less dense fluid. The R-T gravitational instability theory can be used to draw a relationship between the spacing of volcanic structures and edifices at the surface and the depth of the source of instability beneath the volcanic fields (i.e. the lithosphere-asthenosphere boundary depth where partial melting is initiated and starts the vertical upwelling of material). We performed the analyses both on the entire population and on two sub-groups obtained from automatic clustering based on point spacing analysis. Overall, the results obtained from the analysis of the entire population can be considered a global average while the information extracted from the analyses of the two clusters are to be interpreted as end members. Hence, the lithosphere-asthenosphere boundary depth results to be located at 117 ± 10 km underneath Parga.

Additionally, we ran geodynamical models using a variable thermal conductivity and expansivity, and reference viscosities between 1e20 and 1e22 Pa s. These models use an extrusive to intrusive magmatism ratio of 0.1, a typical terrestrial value (Crisp et al., 1984). The intrusive melt is assumed to stall at the base of the crust (~20 km depth; James et al., 2013), since the latter represents a density barrier. According to these models,  a mantle reference viscosity of 1e20 Pa s is best compatible with the geologically inferred lithosphere thickness as well as a thin mechanical thickness as suggested by elastic thickness estimates (e.g., O’Rourke & Smrekar 2018).

As future missions will return higher resolution imagery and topographical information, we suggest the area of Parga chasma as a region of high interest for future data acquisitions. In fact, more detailed data can allow the observation of stratigraphic relationships between rises, rifts, coronae, and volcanoes in order to reconstruct the event sequences. By means of R-T analysis and similar techniques, we would thus be able to refine current analyses and perform more detailed estimates from smaller volcanic features and obtain more precise information about magma reservoir distribution in the subsurface.

How to cite: De Toffoli, B., Mazzarini, F., Plesa, A.-C., Vaujour, T., Breuer, D., and Hauber, E.: Revealing Venus Interior from Coronae Analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-954, https://doi.org/10.5194/egusphere-egu22-954, 2022.

We have used infrared spectra of the dark side of Venus, recorded by the VIRTIS-H spectrometer (Drossart et al. Proc. SPIE 5543, 175, 2014) aboard Venus Express (Svedhem et al. JGR 113, E00B33, 2008), to analyze the CO (1-0) band around 4.7 µm. The resolving power of VIRTIS-H (about 1200) is sufficient to separate the individual lines of CO. We have selected two sets of spectra, the first one at mid-latitude (43°S) and the other in the polar collar (69-83°S). The CO individual lines appear in absorption in the first case, and in emission in the second case, as a consequence of a temperature inversion occurring at high latitude at the level of the upper cloud top. Synthetic models have been calculated using the Planetary Spectrum Generator (Villanueva et al. JQSRT 217, 86, 2018). Information is retrieved on the thermal vertical profile and the CO vertical distribution at both latitudes. This work illustrates the capabilities of high-resolution infrared spectroscopy for monitoring minor atmospheric species in the mesosphere of Venus, in the perspective of the EnVision mission (Helbert et al. Proc. SPIE 11128, A1112804, 2019).

How to cite: Freire, C., Widemann, T., Encrenaz, T., Machado, P., and Dias, J.: Observations of the (1-0) band of CO in Venus using VIRTIS-H aboard Venus Express, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3076, https://doi.org/10.5194/egusphere-egu22-3076, 2022.

The habitability of a terrestrial planet depends on its surface conditions, which can vary greatly during its evolution. Volatile exchanges between the interior, the surface and the atmosphere - the cycles of volatile species or their absence - are largely responsible for these variations and the resulting complex feedback mechanisms between the processes involved. The differences between Earth and Venus climate conditions highlight how similar processes and base characteristics can lead to divergent states after billions of years of evolution. While Venus exhibits hostile conditions and its atmosphere appears mostly desiccated, some hypothetical evolution scenarios suggest it was not always so, and that it could have sustained liquid water oceans for an undefined period of time during its past history. We investigate what mechanisms are likely to be responsible for this type of catastrophic change on Venus and possibly on terrestrial planets, using coupled numerical evolution simulations of planetary evolution, involving mantle dynamics, volcanism, atmospheric greenhouse, escape mechanisms, meteoritic impacts and surface solid-gas exchanges. Increasing solar luminosity (the faint young sun paradox) only marginally affects surface temperature changes. Atmospheric escape could only hide the results of a runaway greenhouse phase by removing water rather than cause the observed climate change. Moreover, it is shown, especially in light of recent measurements interpretation, to be unlikely to be responsible for massive water loss. Large impacts, capable of releasing large amounts of volatiles in the atmosphere, are infrequent and unlikely to occur during late evolution. The smaller impactors do not have enough mass to affect the mantle or atmosphere substantially.  The cause of catastrophic transitions and the means to dessicate the atmosphere of Venus post-runaway greenhouse may be internal. We investigate volcanic gas release based on mantle composition and mantle dynamics over time, as well as oxidation mechanisms of fresh material that can trap volatiles into the surface. Solid surface oxidation is inefficient and appears to be roughly as efficient (within 0.1-1 order of magnitude) as recent atmospheric escape, when considering O removal during the last few billion years. Ashes oxidation could be more efficient but requires explosive volcanism that is not widespread on Venus, given the few traces detected from surface observation. We compare its effects to that on Earth. However, large variations in atmospheric composition and vertical structure resulting from runaway greenhouse could affect all the mechanisms involved in the evolution of terrestrial planets and, under some circumstances lead to a late molten surface phase. Surface exchanges and atmospheric loss would therefore be affected in turn.

How to cite: Gillmann, C. and Golabek, G.: The role of surface volatile exchanges in evolving climate conditions on terrestrial planets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3336, https://doi.org/10.5194/egusphere-egu22-3336, 2022.

Since 2012, we have been monitoring SO₂ and H₂O (using HDO as a proxy) at the cloud top of Venus, using the TEXES high-resolution imaging spectrometer at the NASA InfraRed Telescope Facility (IRTF) at Maunakea Observatory. Maps have been recorded around 1345 cm^-1 (7.4 microns), where SO₂, CO₂ and HDO are observed, and around 530 cm^-1 (19 microns) where SO₂ and CO₂ are observed. An anti-correlation has been found in the long-term evolution of these two species and SO₂ plumes have been identified with an evolution time scale of a few hours. The SO₂ distribution as a function of local time seems to show two maxima around the terminator, indicating the possible presence of a semi-diurnal wave (Encrenaz et al. A&A 639, A69, 2020). After a year of interruption due to the Covid crisis, new observations have been performed in July and September 2021.   They show that the SO₂ abundance, which had been globally increasing from 2014 until 2019, has now decreased with respect to its maximum value. The new data will be analyzed in the context of the whole dataset.

How to cite: Encrenaz, T., Greathouse, T., Giles, R., Widemann, T., Bézard, B., and Fouchet, T.: Ground-based HDO and SO2 thermal mapping on Venus : An update, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3676, https://doi.org/10.5194/egusphere-egu22-3676, 2022.

The Mercury-bound BepiColombo mission passed by Venus for a second gravity assist maneuver (GAM) on the 10^th of August, 2021. During the GAM, the plasma instrumentation on board the two spacecraft Mercury Magnetosphere Orbiter (MMO, JAXA), and Mercury Planetary Orbiter (MPO, ESA), which are stacked together during cruise before orbit insertion at Mercury in 2025, made measurements of the Venusian plasma environment. The entire passage was spent in the Venusian magnetosheath; from the entering of the inbound bow shock at around 12:30 UT, near 8 Rv from the planet, to the exit though the outbound bow shock near the subsolar point at 14:00 UT. This meant that it crossed several different subregions of the magnetosheath, which could be successfully measured and characterised by a combination of the many different plasma instruments on board the MMO and MPO spacecrafts of the BepiColombo mission.

In addition, one day before the Venus GAM for BepiColombo, the Solar Orbiter spacecraft performed a GAM at Venus, with a trajectory after the gravity assist leading upstream of Venus. As a result, the Solar Orbiter provided measurements of the solar wind conditions upstream of Venus during the BepiColombo GAM. Shifting the Solar Orbiter measurements with one hour showed a good correlation between the measurements of the Interplanetary Magnetic Field (IMF) by the two missions (when both were outside of the Venusian bow shock). Therefore, we conclude that Solar Orbiter was connected along the same Parker Spiral arm as Venus during the BepiColombo GAM, and the Solar Orbiter can be used as an upstream solar wind monitor.

Through the combination of the MPPE (Mercury Plasma/Particle Experiment) instrument package onboard MMO, the SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) instrument package and magnetometer onboard MPO, together with the upstream monitor by Solar Orbiter PAS (Proton Alpha Spectrometer) and magnetic field instruments, we have characterized and analysed the subregions of the Venusian magnetosheath. In this presentation we will give an overview of these observations and discuss the larger context of the results.

How to cite: Persson, M. and the BepiColombo and Solar Orbiter Venus subsolar region investigation team: The scenic tour of the Venusian magnetosheath by BepiColombo, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3903, https://doi.org/10.5194/egusphere-egu22-3903, 2022.

The idea of a habitable Venus epoch has gained traction in recent years via 1-D and 3-D General Circulation Modeling (GCM) efforts [1,2,3]. Although recent work has supported an alternative permanent hot and dry scenario [4].  However, the habitable scenario presents us with a conundrum - how does a terrestrial planet transform from temperate to hot-house? For decades it was proposed that the gradual brightening of the sun was the probable cause [5]. Yet 4 billion years ago Venus was receiving nearly 1.4 times the insolation that Earth receives today, and many studies have put Earth at the inner boundary of the habitable zone today [6].  The newer 3-D GCM efforts have demonstrated that if Venus had an early habitable period, that the cloud-albedo feedback responsible for maintaining temperate surface conditions [7] could still be in operation today. From this perspective increasing insolation through time cannot be an answer to the transition from habitable to hot-house. We propose that the 'Great Climate Transition' (GCT) was trigged by simultaneous large igneous provinces (LIPs) akin to those like the Siberian Traps responsible for the End Permian [8].  We have taken the most up to date LIP database for Earth [9] and characterized their distribution through time as random or nearly random. Next we initiate a large suite of Monte Carlo simulations based on this record and generate the likelihood for simultaneous, or environmentally overlapping events in this hypothetical setup. We find the probability of such events to be quite high, a probable cause for Venus' GCT, and a possible harbinger of things to come for Earth.

[1] Grinspoon, D.H. & Bullock, M.A. (2007) AGU https://doi.org/10.1029/176GM12
[2] Way, M. J. et al. (2016) GRL 43, 8376–8383
[3] Way, M. J. and Del Genio, A D.  (2020) JGR Planets 125, e2019JE006276
[4] Turbet et al. (2021) Nature,598,276 https://doi.org/10.1038/s41586-021-03873-w
[5] Kasting J. F., Pollack J. B. and Ackerman T. P. (1983) Icarus, 57, 335-355
[6] Kopparapu, R.K. et al. (2013) ApJ 765, 131
[7] Yang, J. et al. (2014) ApJ 707, L2
[8] Wignall, P. (2001) Earth Science Reviews, 53 (1-2), 1-33
[9] Ernst R. E. et al. (2021) AGU Geophys. Mon. 255, pp. 3-26

How to cite: Way, M., Ernst, R., and Scargle, J.: Heat-death by volcano - how Venus went rogue?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4357, https://doi.org/10.5194/egusphere-egu22-4357, 2022.

For fifteen years, a Global Climate Model (GCM) has been developed for the Venus atmosphere at “Institut Pierre-Simon Laplace” (IPSL), in collaboration between LMD and LATMOS, from the surface up to 150 km altitude (Lebonnois et al., 2010; 2016). Recently, the vertical grid was extended from 10^-5 Pa to 10^-8 Pa (~180-250 km) and allows us to simulate the Venusian upper thermosphere. At the same time, improvements were made on the parameterization of non-LTE CO₂ near infrared heating rates, on the parameterization of non-orographic gravity waves and a tuning was performed on atomic oxygen production to improve the thermospheric densities and their effects (heating and cooling; Martinez et al., 2022; submitted).

This work focuses on validating the modeled thermospheric structure by comparison using data from the Pioneer Venus, Magellan and Venus Express missions which cover similar and complementary (equator and pole) regions at different periods of solar activity, typically above 130 km in altitude. In particular, we will discuss the importance of atomic oxygen in regulating the thermospheric temperature, the effect of the solar cycle on the upper thermosphere and the effect of non-orographic gravity waves on the diurnal temperature profile.

References:

Lebonnois, S., Hourdin, F., Eymet, V., Crespin, A., Fournier, R., Forget, F., 2010. Superrotation of Venus’ atmosphere analyzed with a full general circulation model. J. Geophys. Res. (Planets) 115, 6006. https://doi.org/10.1029/2009JE003458.

Lebonnois, S., Sugimoto, N., Gilli, G., 2016. Wave analysis in the atmosphere of Venus below 100-km altitude, simulated by the LMD Venus GCM. Icarus 278, 38–51. https://doi.org/10.1016/j.icarus.2016.06.004.

Martinez et al. 2022, submitted to Icarus

How to cite: Martinez, A., Lebonnois, S., Millour, E., Pierron, T., Moisan, E., Gilli, G., and Lefevre, F.: Venusian Thermosphere variability by IPSL Venus GCM, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5271, https://doi.org/10.5194/egusphere-egu22-5271, 2022.

Our team has discovered first impact craters under the thick Venusian atmosphere with radar images during the Venera 15/16 mission. Later Magellan radar images of a better quality allowed us to count all impact craters and to find amazing features, splotches, resulted most probably from “airbursts” - total explosive disruption in flight of small celestial bodies. Splotches could have a central feature (possibly caused by terminal impacts of fragments), or could be diffusive patches of increased (bright) or decreased (dark) areas of changed radar reflectivity. The main explanation so far is that atmospheric shock waves, generated by airbursts, somehow change the surface radar reflectivity, e.g. creating smoother (radar dark) or more rough (radar bright) zones due to reflection of shocks. Size of splotches vary from ~10 km to ~200 km, being comparable with the characteristic atmosphere thickness. The exact mechanisms of air shock wave interaction with the surface is still under debates, but promises to help us better understand the presence of dust/sand/pebbles/boulders at the surface of Venus as well as to estimate mechanical properties of surface rocks. We start a small project to support the issue. The project includes the numerical modeling of atmospheric shock waves on Venus due to cratering impacts and due to airbursts. Our modeling is compared with results published in 1990s-2000s. Airbursts are modeled as a hot spheric volume gas explosion 10 to 40 km above the surface in the Venusian stratified atmosphere. In addition to trivial parameters like maximum pressure, dynamic pressure and the wind speed behind the shock front, necessary for the following analysis of a possible “aeolian” motion of surface’s fines, we try to formulate a general picture of shock wave propagation in the atmosphere after an airburst. We find that the large-scale hot gas bubble from the source zone creates a n x 10 km plume (a kind of a classical “mushroom”), which effectively expands laterally at high altitudes, pushing forward an enhanced shock wave. This wave is looking like a gradual conversion of the main shock wave from a hemispheric one to a conic front, returning back to surface. The other trivial (but not discussed quantitatively) phenomenon is the seismic wave, created by an air shock, but finally overrun the atmospheric shock front. It means that the surface air shock front at large distances arrive after the seismic wave shakes the surface. We plan to investigates all these phenomena and compare models with observations. An interesting possibility seems to be satellite observation of rare meteoroid entry to the Venusian atmosphere, as it now available for terrestrial bolides.

How to cite: Ivanov, B.: Impact features on Venus: Modeling craters and splotches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6178, https://doi.org/10.5194/egusphere-egu22-6178, 2022.

Our neighbouring planet Venus holds key insights into terrestrial planet evolution. At present, there is no mosaic of mobile tectonic plates on the planet, yet Venus’ surface is scarred with many tectonic and volcanic structures. Surface deformation seems to be related to regional-scale tectonic deformation and/or mantle upwellings, but it remains questionable exactly when, and how, Venus is resurfacing. “Coronae” are ~circular crown-like structures with traces of tectonic and volcanic activity. They are commonly proposed to be surface manifestations of mantle plume upwellings and/or magmatism, and may therefore provide fundamental insights to Venus’ interior dynamics through time. The exact processes underlying their development and the reasons for their diverse morphologies have been widely debated in the past, with several key outcomes for the Venus scientific community. 

In this presentation, I focus on our recent 3D numerical studyof plume-induced corona formation ^[1] and discuss what insights this study gives on the thermal evolution of Venus, as well as its present-day geological activity. The modelled corona morphologies are strongly on the lithospheric structure and the underlying dynamic processes at play. By a detailed comparison the modeling results with observed corona features (data from NASA’s Magellan mission), widespread plume activity on Venus was identified.  Moreover, I present prompting new results on the gravitational signatures of these modelled corona structures, and discuss whether we can distinguish between different stages of corona evolution in the gravity field. These outcomes may be important for future radio science experiments aboard ESA’s EnVision orbiter.

Finally, I’ll touch upon several key directions for future research on these enigmatic coronae structures, which are relevant in light of the upcoming ‘Decade(s) of Venus Science’. While I mainly formulate these key questions form a geodynamical point-of-view, I invite scientists from all disciplines of the Geo- and Planetary sciences to join the discussion on how these unique coronae can provide key information on the evolution of the interior and surface of Earth’s twin planet.


[1] Gülcher, A.J.P., Gerya, T.V., Montési, L.G.J., and Munch, J., (2020). Corona structures driven by plume–lithosphere interactions and evidence for ongoing plume activity on Venus. Nature Geoscience, 13, 547–554. 

How to cite: Gülcher, A., Gerya, T., and Montési, L.: Corona structures as a window into volcano-tectonic activity on Venus: key insights and ways forward, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7680, https://doi.org/10.5194/egusphere-egu22-7680, 2022.

The Sun exerts tidal forces that deform the planet Venus, from deformation and mass redistribution in its interior, involving variation in the gravity field. The deformation of the planet induced by tidal forcing can be observed with the periodic variations of its gravity field and the Love number k2. The planet’s deformation is linked to its internal structure, most effectively to its density, rigidity and viscosity.  Hence the tidal Love number k₂ can be theoretically estimated  for different planetary models.

The terrestrial planet Venus is reminiscent of the Earth twin planet in size and density, which leads to the assumption that the Earth and Venus have similar internal structures. In this work, the calculation of k₂ is done with ALMA, a Fortran 90 program from Spada [2008] which computes the tidal and load Love numbers using the Post-Widder Laplace inversion formula. With a reference Venus model from Dumoulin et al. [2017], we investigate different parameters of the planet’s layers to calculate its frequency dependent tidal k₂. We apply a random variation of each layer’s parameters within certain boundaries, which allows a statistical analysis of the possible Venus models that fall into the observed data (Mass, Moment of Inertia and k2). We test the effect of different parameters in the Venus model on the k₂ and better understand the different hypotheses for the interior of Venus, as mantle viscosity to core structure (a fluid, solid and part fluid part solid core) .

How to cite: Saliby, C., Briaud, A., Fienga, A., Memin, A., Spada, G., and Melini, D.: The internal structure of Venus and its global deformation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7781, https://doi.org/10.5194/egusphere-egu22-7781, 2022.

On June 10, 2021, the European Space Agency (ESA) announced the selection of EnVision as its newest medium-class science mission. EnVision's overarching science questions are to explore the full range of geoscientific processes operating on Venus [1, 2]. It will investigate Venus from its inner core to its atmosphere at an unprecedented scale of resolution, characterising in particular core and mantle structure, signs of past geologic processes, and looking for evidence of past liquid water. Recent modeling studies strongly suggest that the evolution of the atmosphere and interior of Venus are coupled, emphasizing the need to study the atmosphere, surface, and interior of Venus as a system. The nominal science phase of the mission will last six Venus sidereal days (four Earth years). EnVision will downlink 210 Tbits of science data, using a Ka-/X-band comms system with a 2.5 m diameter fixed high-gain antenna. As a key partner in the mission, NASA provides the Synthetic Aperture Radar, VenSAR.

The EnVision payload consists of five instruments provided by European and US institutions. The five instruments comprise a comprehensive measurement suite spanning infrared, ultraviolet-visible, microwave and high frequency wavelengths. This suite is complemented by the Radio Science investigation exploiting the spacecraft TT&C system. All instruments in the payload have substantial heritage and robust margins relative to the requirements with designs suitable for operation in the Venus environment. This suite of instruments was chosen to meet the broad spectrum of measurement requirements needed to support EnVision science investigations. Two parallel competitive industrial studies will continue in the Definition Phase B1, to complete trade-offs, consolidate requirements and interfaces, produce system specifications,  support development of the science operations, calibration strategies, science products definition under the responsibility of the Future Missions Department (SCI-F) and under the authority of the EnVision Study Manager until Mission Adoption Review (MAR) scheduled in 2024. 

[1] ESA's EnVision Assessment Study Report: sci.esa.int/web/cosmic-vision/envision-assessment-study-report-yellow-book. [2] EnVision mission website: www.envisionvenus.eu.

How to cite: Widemann, T., Ghail, R., Wilson, C., Titov, D., Straume, A. G., Ocampo, A., Bocanegra-Bahamon, T., Bruzzone, L., Campbell, B., Carter, L., Dumoulin, C., Gilli, G., Helbert, J., Hensley, S., Kiefer, W., Marcq, E., Mason, P., Moreira, A., and Vandaele, A. C.: The EnVision Mission to Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8391, https://doi.org/10.5194/egusphere-egu22-8391, 2022.

The investigation of planetary cores is of great interest to those seeking to better understand magnetic fields and the life-processes of planets. Like many large-scale systems, planetary cores are unable to be modelled perfectly by numerical simulations or physical experiments. However, it is of constant importance to improve numerical and experimental methods and designs to better replicate full-scale processes. Many previous studies have over-looked the effects of the inhomogeneous insulation from the Earth's mantle on convection in the core. A few numerical studies have taken this effect into consideration for rotating Rayleigh-Benard convection (RBC) in spherical geometries. Experimental models are desirable to further understand the motion of fluid in the center of planets; however, due to physical limits, spherical systems are difficult to recreate experimentally. Therefore, cylindrical geometries are useful to study varied thermal flux on sidewalls both experimentally and numerically. While some studies have numerically and experimentally considered changes in temperature along the sidewall, there has been little consideration for variations in heat flux, which is the more physically appropriate boundary condition. 

The present study seeks to explore rotating RBC in a cylindrical domain with sidewalls inhomogeneously insulated in an experimentally-achievable system. It is experimentally plausible that the material of a cylindrical cell could varying in thickness, and therefore thermal conductivity, or have patches of heating and/or cooling attached to the sidewall to vary the thermal flux on the side boundaries. To imitate this numerically, a sinusoidal pattern of increasing and decreasing heat flux is applied to the sidewall in two cases: one whereby heat flux fluctuates between positive and negative, and another whereby the heat flux is strictly positive. Additionally the mode and amplitude of the wave is considered. The mode will either match the mode of the system with insulating sidewall conditions or have a larger wavelength to better simulate planetary cores. The amplitude is increased as necessary to achieve significant results. For simplicity, the top and bottom boundary conditions are fixed temperature.

Changes in heat transport and temporal behavior are measured with a global Nusselt number, Nu, time series. Additional variables such as mean zonal flow, number and location of convection rolls, and transitions to time-dependence are considered. Results indicate that large-wavelength heat flux on the sidewalls causes two modes to inhabit the system, existing on opposite sides of the cylinder: the mode natural to the homogeneously insulated system exists where heat flux is high and a large-wavelength mode dominates where heat flux is lower. However, the implementation of heat flux along the sidewalls with the same wavelength of the insulated system results in near-time independence as the amplitude increases. These results indicate that variation in heat flux boundary conditions can cause significant changes in rotating RBC behavior. Experimental studies could be used to validate or refute these conclusions. Overall, it is clear that numerical studies of molten planetary cores heterogeneously heated by mantles must take these irregularities into consideration to improve our understanding of core convection. 

How to cite: Peifer, J., Bokhove, O., and Tobias, S.: Changes in pattern formation and behavior in rotating Rayleigh-Benard convection due to inhomogeneous thermal insulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-134, https://doi.org/10.5194/egusphere-egu22-134, 2022.

It was often shown how the anisotropy (due to turbulence) in the Earth’s outer core strongly influences some convection processes very important in the Core Dynamics. For instance, it was described how some instabilities in rotating magnetoconvection, described as usually by the analysis in term of normal modes, depend strictly on the anisotropic diffusion. Thus, we developed many models concerning the marginal modes (stationary and oscillating modes) of rotating magnetoconvection with different cases of anisotropy in the viscosity, thermal and magnetic diffusivities. In all cases, an anisotropy greater in the vertical direction parallel to gravity (“atmospheric anisotropy”) facilitates the convection, while an anisotropy greater in horizontal directions (“oceanic anisotropy”) inhibits some types of convection. This is linked with the balance among Magnetic, Archimedean and Coriolis forces in the Earth’s outer core.  

After recalling these former results concerning marginal modes, we present new results concerning the most unstable modes, namely the ones with maximum growth rate, with isotropic and anisotropic diffusivities.

Firstly, the state of the art about this topic in isotropic conditions is reminded, then our new approach on it is presented. We show that assuming a time-dependence only in the temperature perturbation (we call it T-case), like it was done in some former works, does not describe properly these modes in the Earth’s outer core. Indeed, this implies that some types of convection would occur only with some values of the dimensionless numbers unrealistic for the Earth (e.g., with too huge values of the Ekman numbers). We study the most general isotropic case (and we christen it G-case), namely the most unstable modes of convection with temperature, velocity and magnetic perturbations time-dependent. In this case the convection is much more facilitated than in the T-case: it occurs with much smaller values of Ekman and Elsasser numbers. Another model (named by us Q-case) with very small magnetic Prandtl number, namely with magnetic diffusivity much greater than viscosity, is considered. The Q-case results are very similar to the G-case ones. We demonstrate (and indicate) that Q and G cases can hold for the Earth (and for other planets).

We show that the anisotropy strongly influences the most unstable modes. Indeed, like in the marginal ones, the atmospheric anisotropy facilitates the occurrence of the most unstable modes convection, while the oceanic one inhibits it. Furthermore, we prove that, in contrast with isotropic case, in case of strong oceanic anisotropy the differences between Q and G cases can be significant for the Geodynamo.

Our approach allows to easily deal with very huge wave numbers and Rayleigh numbers as well as with very small Ekman numbers, what is usually not possible in the standard geodynamo simulations. This aspect and the growth rates search are useful to look for possible connections with small length and time scale analysis of the Geomagnetic field. 

How to cite: Filippi, E. and Brestenský, J.: The most unstable modes in rotating magnetoconvection with anisotropic diffusion in the Earth’s outer core, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-189, https://doi.org/10.5194/egusphere-egu22-189, 2022.

Although the solidity of Earth’s inner core is evidenced by normal mode data, the direct observation of inner core shear waves (J-waves) has remained challenging for decades due to their small amplitudes. Previous studies have presented evidence of J-waves in different seismic datasets (e.g., Okal and Cansi Y, 1998; Deuss et al., 2000; Cao et al., 2005; Wookey and Helffrich, 2008), however, the observability seems to be highly dependent not only on distance, but also on the location of the source and receiver, suggesting that amplification from specific 3D structures in the deep Earth is necessary to elevate the phase above noise for certain ray paths. Waszek and Deuss (2015) and Tkalčić and Phạm (2018) also found J-waves in global stacks and global correlation wavefield respectively, but these average over all possible source-receiver geometries and inner core structure.

To improve phase identification and discrimination, we use an approach that combines the array method of slant stacking and polarization filtering to enhance linearly polarized signals with the expected slowness and incident angle. We apply this technique on the data of the AlpArray Seismic Network, a large-scale seismic network in Europe that consists of over 600 broadband stations with a mean station spacing of 30-40km. An arrival consistent with PKJKP (in reference travel time, slowness, and polarization) is found from events in the source region reported by Cao et al. (2005). We present an overview of PKJKP candidate paths over distance based on observations with AlpArray. We also examine whether these observations correspond to specific depths or azimuths and investigate the effects of anisotropy or other three-dimensional earth structures​​​​​​.

How to cite: Ling, O. K. A., Stähler, S., Kim, D., Giardini, D., and AlpArray Working Group, T.: Observations of Inner Core Shear Waves with AlpArray, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1088, https://doi.org/10.5194/egusphere-egu22-1088, 2022.

Various types of waves exist in the Earth’s core. Waves associated with the magnetic field can leave a signature in the observed geomagnetic field, which may allow one to infer properties of the core. Among those, a balance of magnetic, Coriolis and pressure forces forms a type of waves known as Magneto-Coriolis (MC) waves. Previous studies of MC wave have mostly been focused on the ideal limit (without magnetic diffusion and viscous dissipation) with a columnar ansatz for the flow field. In this study, we investigate this problem by retaining the magnetic diffusion and three-dimensional flows in a full sphere. With several choices of axisymmetric background magnetic field, we analyse various branches of normal modes. The dependence of the normal mode's structure on the background field is clearly seen. A westward propagating branch with perfect columnar flows is found for some background B. We have also found eastward propagating modes constituted by flows with weaker columnarity. With the choice of Elsasser number Λ=1 (Coriolis and magnetic forces of similar magnitude), for axisymmetric background fields we find most of the MC modes have decay rates comparable or larger than their frequencies.

How to cite: Luo, J., Jackson, A., and Marti, P.: Waves in the Earth’s core. 2: Diffusive Magneto-Coriolis waves., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2363, https://doi.org/10.5194/egusphere-egu22-2363, 2022.

Light elements play a key role in the chemical and physical processes of planetary Fe-rich metallic cores [1].  H and Si are believed important candidates in planetary cores and previous estimates indicate as much as 0.6 wt% H and 13 wt% Si in the Earth’s core [2, 3]. However, existing studies are on Fe-H or Fe-Si binary systems and knowledge on Fe-Si-H ternary at high pressure and temperature is still limited [4, 5]. We conducted a series of experiments to understand the impact of hydrogen on Fe-Si alloy system. Fe-Si alloys with three compositions, Fe-9Si (9 wt% Si), Fe-16Si (16 wt% Si), and FeSi (33.3 wt% Si), reacted with H separately up to 125 GPa and 3700 K in diamond-anvil cells by combining pulsed laser heating with high-energy synchrotron X-ray diffraction. Results show little H solubility in B20 and B2 phases of FeSi (0.3 wt% and <0.1 wt% H, respectively) up to 62 GPa, which is significantly smaller than H solubility in Fe metal (1.8 wt% H) [6]. The low H solubility in these phases is likely because of their highly distorted interstitial sites which are not favorable for H incorporation. We found that the low-Si alloys (Fe-9Si and Fe-16Si) convert into FeH_x (fcc or dhcp), FeSi (B20 or B2), and Fe-Si-H ternary phases up to 125 GPa and 3700 K. Particularly, a Fe₅Si₃H_x phase is stable below 43 GPa and the cubic FeH₃ can appear after reactions above 100 GPa. These results indicate that H alters the behavior of the Fe-Si system severely. Considering the various sizes and masses of planets in the solar and exoplanetary systems, the planetary cores can have a wide range of Si contents. If Fe-droplets in early magma ocean contain much Si, Si could limit the amount of H incorporated in the core. On the other hand, for cores with low Si, crystallization at the solid-liquid core boundary may result in formation of separate H-rich and Si-rich crystals in the solid core, potentially inducing heterogeneities in the region [7]. 

References:

1. Shahar, A., et al., What makes a planet habitable? Science, 2019. 364(6439): p. 434-435.

2. Tagawa, S., et al., Experimental evidence for hydrogen incorporation into Earth’s core. Nature Communications, 2021. 12(1): p. 2588.

3. Hirose, K., B. Wood, and L. Vočadlo, Light elements in the Earth’s core. Nature Reviews Earth & Environment, 2021. 2(9): p. 645-658.

4. Terasaki, H., et al., Hydrogenation of FeSi under high pressure. American Mineralogist, 2011. 96(1): p. 93-99.

5. Tagawa, S., et al., Compression of Fe–Si–H alloys to core pressures. Geophysical Research Letters, 2016. 43(8): p. 3686-3692.

6. Pépin, C.M., et al., New iron hydrides under high pressure. Physical review letters, 2014. 113(26): p. 265504.

7. Deuss, A., Heterogeneity and anisotropy of Earth's inner core. Annual Review of Earth Planetary Sciences, 2014. 42: p. 103-126.

How to cite: Fu, S., Chariton, S., Prakapenka, V., Chizmeshya, A., and Shim, S.-H.: Phase Relations in the Fe-Si-H Ternary up to 125 GPa and 3700K: Implications for the Structure and Chemistry of Planetary Cores, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3229, https://doi.org/10.5194/egusphere-egu22-3229, 2022.

Increasing seismic evidence has accumulated, suggesting that the Earth’s outer core consists of distinct layers of low P-wave velocities relative to the Preliminary Reference Earth Model (PREM) in the top and bottom of the liquid core. Seismically detected low velocity in the outer core could be linked with the stratification, essential for understanding the geodynamo and thermochemical evolution of the liquid core. However, a consistent globally-averaged radial structure of the outer core has not been obtained due to the incomplete coverage of sampling body waves. To remedy this problem, we explore the seismic structure of Earth's outer core by employing a new theoretical and observational concept termed coda correlation wavefield. We construct the global correlogram in the 15-50 sec period range by stacking cross-correlations of the long-duration coda waves from the selected ten large earthquakes. We then assemble a dataset of prominent correlation features from the global correlogram that are sensitive to the outer core. The waveforms of these features are fit by computing synthetic correlograms through various outer core models. The obtained optimal model displays P-wave velocities in both the outer core's top and bottom, consistent with Coda Correlation Reference Earth Model (CCREM) and reduced relative to PREM. The low seismic speeds in the top of the outer core could likely imply the formation of a thermal and/or compositional stratification.

How to cite: Ma, X. and Tkalčić, H.: CCMOC: A New View of the Earth's Outer Core Through the Global Coda Correlation Wavefield, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3349, https://doi.org/10.5194/egusphere-egu22-3349, 2022.

Global seismic imaging of the Earth's interior has come a long way in exploring and understanding the Earth’s internal structure and dynamics with the worldwide proliferation of seismographs. However, investigating planetary interiors, including detections of their deep structures, remains challenging because of the limited number of seismographs that are and will be deployed in the foreseeable future. Besides, the existing imaging methods based on observations of a direct seismic wavefield from seismic sources require the emergence of the seismic waves with distinguishable amplitudes. That condition restricts the seismic station locations for practical wave reflections or refractions from internal planetary interfaces to a limited angular distance range from the source.

Here, we explore a new way to image deep planetary interiors, especially the planetary cores, using a single seismograph. We first develop a novel procedure for constructing global inter-source correlograms and show that they contain many prominent features sensitive to the internal planetary structures. We demonstrate that a single station is sufficient to produce a global correlogram for the Earth. We then utilize a single-station correlogram and show the steps for detecting and quantifying the Earth’s and Martian cores interfaces. This provides a new paradigm for imaging deep planetary interiors on global scales.

How to cite: Wang, S. and Tkalčić, H.: Imaging of Deep Planetary Interiors from Inter-source Correlations via a Single Seismograph, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3362, https://doi.org/10.5194/egusphere-egu22-3362, 2022.

Top-down solidification has been suggested in the liquid cores of small planets, moons, and large asteroids. An iron snow is then thought to exist, consisting of the crystallization of free iron crystals at the top of these cores and of their settling in a stably stratified ambient, until they remelt in a hotter, deeper region. This inward crystallization and associated buoyancy flux may sustain dynamo action by convection below the remelting depth. However, thermal evolution models are up-to-now oversimplified, assuming a constant-in-time and homogeneous-in-space buoyancy flux at the bottom of the snow zone. We have shown from analog experiments that the buoyancy flux is heterogeneous in time and space, with intense snow events, corresponding to an explosion of frazil-ice,  separated by quiescent periods where the snow zone supercools. We found that a wide range of crystal sizes exists, with large crystals overshooting the convection region and challenging the thermodynamic equilibrium hypothesis underlying the evolution models. The spatio-temporal variability of the energy source obviously impacts the shape and intensity of the generated magnetic field, which may provide alternative explanations for the observed and surprising features of Mercury's and Ganymede's magnetic fields.

How to cite: Huguet, L. and Le Bars, M.: A laboratory model for iron snow in planetary cores, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3740, https://doi.org/10.5194/egusphere-egu22-3740, 2022.

The Earth’s rotation is not perfectly steady: both its rotation rate (its spin rate) and its orientation in space change in time due to the gravitational pull of the Sun and Moon. The precession-nutation response of the Earth to this external tidal forcing depends strongly on the planet’s deep interior structure. 
In particular, the existence of the Earth’s liquid outer core is known to produce a resonance in the nutation signal at a near-diurnal frequency (as measured in the Earth-bound rotating frame). Physically, this resonance corresponds to the excitation of free mode whereby the liquid core experiences a global rotation of uniform vorticity, hence its name: Free Core Nutation (FCN). 

In parallel, experimental and theoretical studies of fluid dynamics have since long demonstrated that rotating fluids can support oscillatory motions known as inertial waves, which are due to the restoring effect of the Coriolis force. In planetary situations where the fluid domain is bounded by solid boundaries, these oscillations become global, so that they are sometimes referred to as inertial modes. The Spin-Over Mode (SOM), is the simplest of these inertial mode, with uniform vorticity. Because of this and the fact that the SOM, like the FCN, has a near-diurnal frequency, the two modes have often been identified as one and the same. In a former study, we showed that the FCN is in fact a generalization of the SOM to the case of a (non-steadily) freely rotating planet (Rekier et al 2020). 

In the present work, we analyse the relation between the SOM and the FCN in more details by showing how the two modes can, in fact, coexist together in a planet subjected to external gravitational forcing. We also show that the proximity between the frequencies of the SOM and the FCN can have a significant effect on the shape and the intensity of the FCN resonance – represented by the transfer function for nutations – when viscous and/or electromagnetic coupling is introduced at the planet’s Core-Mantle Boundary (CMB). In particular, we estimate that this can cause an increase of ∼1 day in the (retrograde) period of the resonance as measured in the inertial frame. 

We conclude with a discussion on some of the implications of our findings for the nutations of other planetary objects like Mars and the Moon.

Reference:

• Rekier, J., Trinh, A., Triana, S. A., & Dehant, V. (2020). Inertial modes of a freely rotating ellipsoidal planet and their relation to nutations. The Planetary Science Journal, 1(1), 20

How to cite: Rekier, J.: The Spin-Over Mode of freely rotating planets and its relation to their Free Core Nutation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3972, https://doi.org/10.5194/egusphere-egu22-3972, 2022.

The South Atlantic Anomaly (SAA) is a region at Earth’s surface where the intensity of the magnetic field is particularly low. Accurate characterization of the SAA is important for both fundamental understanding of core dynamics and the geodynamo as well as societal issues such as the erosion of instruments at surface observatories and onboard spacecrafts. Here, we propose new measures to better characterize the SAA area and center, accounting for surface intensity changes outside the SAA region and shape anisotropy. Applying our characterization to a geomagnetic field model covering the historical era, we find that the SAA area and center are more time dependent, including episodes of steady area, eastward drift and rapid southward drift. We interpret these special events in terms of the secular vari‑ation of relevant large‑scale geomagnetic flux patches on the core–mantle boundary. Our characterization may be used as a constraint on Earth‑like numerical dynamo models.

How to cite: Amit, H., Terra-Nova, F., Lézin, M., and Trindade, R.: Non-monotonic growth and motion of the South Atlantic Anomaly, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4635, https://doi.org/10.5194/egusphere-egu22-4635, 2022.

We present pymagglobal, a simple to use python interface for global geomagnetic field models. Pymagglobal was developed to provide easy access to global, spherical harmonics based magnetic main field models over historical and paleomagnetic times. The software readily handles cubic-spline based geomagnetic field models stored in the same file format as gufm1 or the CALSxk model series out of the box. Models in other file formats can be incorporated with minimal effort using the python backend. The python interface can, e.g., give model curves for any location, time series of dipole moment or spherical harmonic coefficients or grids and maps of magnetic field components. 

Pymagglobal can be installed by a single command and comes with a command line interface and a GUI, that allows easy extraction and visualization of information from the models. Additionally, the python backend can be used to access the models, for example to generate synthetic data or refer to them in your own analysis. Emphasis is put on documentation and accessibility. The package is available via a git repository  and a custom website at https://git.gfz-potsdam.de/sec23/korte/pymagglobal.

How to cite: Schanner, M. A., Mauerberger, S., and Korte, M.: A python interface for global geomagnetic field models: pymagglobal, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4857, https://doi.org/10.5194/egusphere-egu22-4857, 2022.

Geomagnetic field models are essential in the study of the physical processes that contribute to the Earth’s magnetic field. There are several groups that build models of the Earth’s magnetic field. These models essentially differ in the magnetic data and mathematical methods used during the model estimation, and in the represented sources of the geomagnetic field. It is then the users who choose the models that are most suitable for the study of the geophysical signals of interest. However, there is currently no single platform where field models are collected in a standardised way, and that provides information which helps users to find the best models for their purposes.

Here, we present the geomagnetic field model called CHAOS that is developed and regularly updated by the Technical University of Denmark. CHAOS provides estimates of the recent time-dependent and static internal magnetic fields, and the external magnetospheric field during quiet geomagnetic conditions. It is derived from magnetic data collected by the Swarm, CHAMP, Ørsted, SAC-C, CryoSat-2 satellite missions supplemented by ground observatory data. It is updated approximately every 4 months with the latest ground and satellite data; the current version CHAOS-7.9 covers the time from 1997 to November 2021.

The model is distributed in various formats. For the time-dependent internal field, B-spline coefficients for each spherical harmonic are provided in a similar format as traditionally used for the gufm1 historical field model and the CALS7K millennial timescale models. It is also provided in the shc-file format, which was developed and adopted for distributing spherical harmonic models determined in connection with the Swarm magnetic satellite mission. This format allows reconstruction of spline-based models from a dense sampling of the time series of the spherical harmonic coefficients and is easier for non-experts to use. A piecewise polynomial Matlab version is also available. For reading and evaluating the CHAOS model, we provide Fortran, Matlab and Python software. In particular, we have recently developed the ChaosMagPy Python package, which allows the CHAOS model (and other spherical harmonic field models) to be easily evaluated and visualized.

Although the shc-file format and ChaosMagPy have been developed primarily in support of the Swarm mission and the CHAOS model, they can be used more broadly for time-dependent spherical harmonic field models or serve as a starting point for the development of new tools that enable cross-disciplinary sharing of data and models.

How to cite: Kloss, C., Finlay, C. C., and Olsen, N.: Tools for sharing and evaluating the CHAOS geomagnetic field model and the shc-file format for time-dependent spherical harmonic models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6265, https://doi.org/10.5194/egusphere-egu22-6265, 2022.

An ever-expanding catalogue of satellite data has laid the foundations for new studies of Earth’s secular variation and acceleration. Studies that encode a-priori the axial rigidity conferred to core flows by the Earth’s rapid rotation have revealed novel fast dynamics and improved estimates for the magnetic field strength inside the core. Within this context, a new formalism christened “plesio-geostrophy” (PG) was developed by Jackson and Maffei (Proc. Roy. Soc. A, 476(2243), 2020) with the purpose of describing core dynamics in a regime closer to Earth's conditions. This model makes use of axial integration of the equations of fluid motion and magnetic induction to collapse all three-dimensional quantities into two-dimensional scalars. We report on new results within the PG formalism.

We consider the dynamics of a conducting, inviscid fluid in a full sphere subject to various background magnetic fields. The eigenmodes sustained by the Coriolis and Lorentz forces split into two branches: a fast and a slow one. We characterise these eigenmodes and compare their structure and frequency to fully three-dimensional results. Previous studies are extended by incorporating the effects of horizontal magnetic diffusion.

How to cite: Holdenried-Chernoff, D., Jackson, A., and Maffei, S.: A comparison between the magnetohydrodynamical modes of plesio-geostrophy and fully 3D calculations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6447, https://doi.org/10.5194/egusphere-egu22-6447, 2022.

It has been proposed that thermoelectric (TE) currents may be important in the vicinity of planetary core boundaries (Stevenson 1987, EPSL; Giampieri & Balogh 2002, P&SS). However, TE-induced core dynamics remain largely unstudied. To address this, we have conducted a series of laboratory experiments of turbulent Rayleigh-Bénard convection with a vertical magnetic field in a cylindrical cell filled with liquid gallium. Thermal measurements are taken at a fixed buoyancy forcing with varying Lorentz force. When buoyant inertia dominates, a large-scale overturning circulation cell develops, which imposes strong lateral temperature gradients onto the tank's top and bottom boundaries. In experiments equipped with electrically conducting boundaries, the large-scale circulation slowly precesses in azimuth when thermoelectrically induced Lorentz forces become comparable to buoyant inertial forces. Moreover, TE introduces an asymmetry in the system: this novel magnetoprecessional mode reverses its traveling direction when the magnetic field polarity is reversed. Extrapolating our results to Earth's core, we estimate the required net Seebeck coefficient to generate TE dynamics at CMB conditions. Furthermore, because TE-driven flows reverse direction as the magnetic field reverses, we hypothesize that thermoelectricity can provide a natural symmetry breaker by driving CMB (or ICB) core flows in opposite directions between normal and reversed geomagnetic field polarities. To test our hypothesis, we need to better constrain the electrical, thermal conductivity, and Seebeck coefficient of the CMB (or ICB), and gather observational evidence of geomagnetic secular variation during field reversals. This study is reported in Xu et al. 2022, JFM

How to cite: Xu, Y., Horn, S., and Aurnou, J.: A laboratory study of turbulent magnetoconvection: Could thermoelectricity induce asymmetry in geomagnetic secular variation?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6590, https://doi.org/10.5194/egusphere-egu22-6590, 2022.

The recent Kalmag and archaeomagnetic ArchKalmag14K models together represent the global geomagnetic field model evolution over the past 14000 years and resolve temporal scales of the order of a month over the last 122 years. They are obtained through the sequential assimilation of archeomagnetic and volcanic data, and survey, observatory and satellite data, respectively. Both these models provide full posterior information about the core field, and in the case of Kalmag also about other magnetic sources such as the lithospheric or some tidal fields. These models are made accessible online through different physical and statistical quantities associated with them. In this presentation, we will detail our modeling strategy, the type of results we are getting with it, and how the community can access and use our models by an online interface at https://ionocovar.agnld.uni-potsdam.de/Kalmag/ and https://ionocovar.agnld.uni-potsdam.de/Kalmag/Archeo/.

How to cite: Baerenzung, J., Schanner, M. A., Korte, M., Saynisch, J., and Holschneider, M.: The Kalmag and ArchKalmag14K geomagnetic field models: their derivation principle, properties and availability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7290, https://doi.org/10.5194/egusphere-egu22-7290, 2022.

We bring together two important features of planetary cores: 1) wave propagation in the fluid and 2) topography of the fluid-solid interface. On one hand, inertial waves contribute to the maintenance of quasi geostrophic motions or to the formation of elongated structures in rotating turbulence. On the other hand, topography of the core-mantle boundary has been prososed in various seismological and geodynamical studies and can modify the fluid flow in the core, for example, by altering global fluid modes. Here, we focus on inertial waves excited by topography.

We present results from a combined numerical and experimental investigation of inertial wave motion which is forced by an oscillating topography. To allow comparison with the theory of linear inertial waves, we use a complex topography characterised by a single wavenumber in the spectral domain. Both, the wavenumber and the frequency of the oscillations are varied, allowing us to characterise the transport of kinetic energy at different length scales as well as the interactions of direct and reflected inertial waves. 

How to cite: Burmann, F. and Noir, J.: Inertial waves excited by topography, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8071, https://doi.org/10.5194/egusphere-egu22-8071, 2022.

The internal magnetic field of Mercury is best described by a northward offset dipole with almost zero obliquity. Its offset, weakness, axisymmetry and lack of secular variation still poses a challenge to dynamo theory. After NASA’s Mariner 10 flybys in the 1970’s and MESSENGER’s orbital mission in 2011-2015, BepiColombo performed a flyby at Mercury in October 2021. For the first time, magnetic field measurements are obtained from the southern hemisphere by the fluxgate magnetometer MPO-MAG. We will present an overview of the flyby data and compare the new in-situ data to magnetospheric models obtained from the previous missions to the innermost terrestrial planet. Does the flyby data reveal any secular variation? Has the dipole offset changed? These are some of the questions we will discuss with this unprecedented magnetometer data. We will close with a discussion on what is to be expected from the orbital phase of BepiColombo. 

How to cite: Heyner, D., Carr, C., Auster, U., Richter, I., Kolhey, P., Exner, W., Mieth, J., Plaschke, F., Pump, K., Wicht, J., Langlais, B., Berghofer, G., Schmid, D., Baumjohann, W., Fischer, D., Horbury, T., Magnes, W., Masters, A., Slavin, J., and Glassmeier, K.-H. and the MPO-MAG Team: BepiColombo at Mercury: First close-in magnetic field measurements from the southern hemisphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8509, https://doi.org/10.5194/egusphere-egu22-8509, 2022.

Since the discovery of Mercury’s peculiar magnetic field it has raised questions about the underlying dynamo process in its fluid core. The global magnetic field at the surface is rather weak compared to other planetary magnetic fields, strongly aligned to the planet's rotation axis and its magnetic equator is shifted towards north. Especially the latter characteristic is difficult to explain using common dynamo model setups. One promising model suggests that a thermal stably stratified layer right underneath the core-mantle boundary is present. As a consequence the magnetic field deep inside the core is efficiently damped by passing through the stably stratified layer due to the skin effect. Additionally, the non-axisymmetric parts of the magnetic field are vanishing, too, such that a dipole dominated magnetic is left at the planet’s surface. In this study we present new direct numerical simulations of the magnetohydrodynamical dynamo problem which include a stably stratified layer on top of the outer core, which can also reproduce the shift of the magnetic equator towards north. We revisit a model configuration for Mercury’s dynamo action, which successfully reproduced the magnetic field features, in which core convection is driven by thermal buoyancy as well as compositional buoyancy (double-diffusive convection). While we find that this model configuration produces Mercury-like magnetic field only in a limited parameter range (Rayleigh and Ekman number), we show that also a simple codensity model is sufficient over a wide parameter range to produce Mercury-like magnetic fields.

How to cite: Kolhey, P., Heyner, D., Wicht, J., Gastine, T., and Plaschke, F.: Dynamo models reproducing the offset dipole of Mercury’s magnetic field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8532, https://doi.org/10.5194/egusphere-egu22-8532, 2022.

Many studies have suggested silicon as a candidate light element for the cores of Earth and Mercury. However, the effect of silicon on the melting temperatures of core materials and thermal profiles of cores is poorly understood, due to disagreements among melt detection techniques, uncertainties in sample pressure evolution during heating, and sparsity of studies investigating the combined effects of nickel and silicon on the phase diagram of iron. In this work (Dobrosavljevic et al. 2022), we develop a multi-technique approach for measuring the high-pressure melting and solid phase relations of iron alloys and apply it to Fe_0.8Ni_0.1Si_0.1 (Fe-11wt%Ni-5.3wt%Si), a composition compatible with recent estimates for the cores of Earth and Mercury.

This approach combines results (20-83 GPa) from two in-situ techniques: synchrotron Mössbauer spectroscopy (SMS) and synchrotron x-ray diffraction (XRD). Melting is independently detected by the loss of the Mössbauer signal, produced exclusively by solid-bound iron nuclei, and the onset of a liquid diffuse x-ray scattering signal. The use of a burst heating and background updating method for quantifying changes in the reference background during heating facilitates the determination of liquid diffuse signal onsets and leads to strong reproducibility and excellent agreement in melting temperatures determined separately by the two techniques. XRD measurements additionally constrain the hcp-fcc phase boundary and in-situ pressure evolution of the samples during heating.

We apply our updated thermal pressure model to published SMS melting data on fcc-Fe and fcc-Fe_0.9Ni_0.1 to precisely evaluate the effect of silicon on melting temperatures. We find that the addition of 10mol% Si to Fe_0.9Ni_0.1 reduces melting temperatures by ~250 K at low pressures (<60 GPa) and flattens the hcp-fcc phase boundary. Extrapolating our results, we constrain the location of the hcp-fcc-liquid quasi-triple point at 147±14 GPa and 3140±90 K, which implies a melting temperature reduction of 500 K compared with Fe_0.9Ni_0.1. The results demonstrate the advantages of combining complementary experimental techniques in investigations of melting under extreme conditions.

Reference:

Dobrosavljevic, V. V., Zhang, D., Sturhahn, W., Zhao, J., Toellner, T. S., Chariton, S., Prakapenka, V. B., Pardo, O. S., Jackson, J. M. (2022). Earth and Planetary Science Letters (in press).

How to cite: Dobrosavljevic, V., Zhang, D., Sturhahn, W., Zhao, J., Toellner, T., Chariton, S., Prakapenka, V., Pardo, O., and Jackson, J.: Melting and phase relations of Fe-Ni-Si determined by a multi-technique approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8916, https://doi.org/10.5194/egusphere-egu22-8916, 2022.

The geodynamo inside the liquid core is part of the Earth’s rotation. We discovered that electric currents in the heat exchanging liquid core need to follow the handedness of the spiraling liquids given by Coriolis force. Coriolis force splits the buoyant heat exchanging liquid into the two, north and south hemispheres, each with its unique handedness of spiraling convection systems. Convection spiraling model of the core fluid revealed that any planetary dynamo with a liquid conducitng core must have a two-component bimodal structure magnetic contribution, where, for Earth, the southern hemisphere is always associated with a dominating normal polarity component and northern hemisphere with a dominating component of reverse magnetic polarity. We show that the geodynamo would have a non-random distribution of the probability of generation of dynamo’s magnetic polarity, depending on a difference in a degree of buoyancy vigorousness between the two hemispheres.  In this work, the individual treatment of normal and reversed polarity durations revealed that while before 80 Ma geodynamo was generating predominantly normal polarity durations, after the Tertiary transition at ~ 60 Ma, the geodynamo produced predominantly reverse polarity durations. This observation of predominance of magnetic polarity durations is constrained by the existing temperature models near the core/mantle boundary (CMB) and we show a novel connection how a lower mantle temperature distribution may reorganize its convection pattern in the core and change the stability of the dipolar field in favor of a specific polarity.

How to cite: Kletetschka, G.: Chirality of the Geodynamo from the Core’s buoyancy and Sense of Spinning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9908, https://doi.org/10.5194/egusphere-egu22-9908, 2022.

Seismic anisotropy observations indicate the presence of an innermost and outermost inner core, but the origin of this structure is unknown. Records of the past geomagnetic field provide a means to probe inner core evolution by establishing when growth started. The Ediacaran (~565 million-year-old) geodynamo was near collapse, with a strength 10 times weaker than that of the present-day consistent with model predictions for the field before the onset of inner core nucleation. But the timing of the key transition to stronger intensities typical of the Phanerozoic Eon, needed for establishing an exact onset age, has been unclear. We present single crystal paleointensity results from anorthosites of the early Cambrian (~532 million-year-old) Glen Mountains Layered Mafic Complex (Oklahoma). Data from single plagioclase crystals bearing single domain magnetite and titanomagnetite inclusions yield a time-averaged dipole moment of 3.5 +/- 0.9 x 10²² A m², 5 times greater than that recorded in the Ediacaran Period. This rapid field recovery is the expectation at the start of inner core growth, as new thermal and compositional sources of buoyancy to power the geodynamo become available. We will discuss thermal models, which together with our new paleointensity results, allow us to constrain growth of the inner core and when its structure may have changed.

How to cite: Zhou, T., Tarduno, J., Cottrell, R., and Nimmo, F.: Early Cambrian renewal of the geodynamo and the origin of inner core structure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10532, https://doi.org/10.5194/egusphere-egu22-10532, 2022.

Taking advantage of the Swarm three-satellite magnetic field mission by ESA, launched on 22 November 2013 and still orbiting, and ground observatory magnetic data, we determine a spatiotemporal regional model for the geomagnetic field using the R-SCHA technique over the area comprising the South Atlantic Anomaly (SAA). The SAA is the region above the South Atlantic and South America where the geomagnetic field intensity is much lower than expected by a simple dipolar field. Its origin is deep in the outer core and is likely due to a reverse magnetic flux area that has been increasing in the last four centuries. On the basis of this model, we observe 1) the recent evolution of the anomaly from 2014 up to date, with a focus on its “tails” towards South Africa and West Pacific, 2) some features that can be related to important properties of the main geomagnetic field, such as its secular variation and the occurrence of geomagnetic jerks.

How to cite: Campuzano, S. A., De Santis, A., and Pavón-Carrasco, F. J.: Regional geomagnetic field model over the area comprising the South Atlantic Anomaly, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11293, https://doi.org/10.5194/egusphere-egu22-11293, 2022.

Given their small sizes and low central pressures, the cores of most asteroids are expected to have started crystallising at the core mantle boundary (CMB) instead of at their centre, as is the case for the Earth. This so-called top-down crystallisation is thermally unstable but compositionally stable, making the conditions for dynamo generation more difficult to achieve. Nevertheless, modern observations of Ganymede show an active magnetic field, where it has been suggested that solidification occurs away from the CMB as an iron snow. This model proposes that iron crystals grow in a snow zone and subsequently sink into the interior and melt, releasing dense fluid that drives convection and a magnetic field. However, whether this process could have occurred in asteroid cores is uncertain due to the significantly smaller adiabatic temperature difference between the CMB and the centre of their cores. This weak temperature gradient may also prevent crystallisation away from the CMB. Therefore, the power for a compositional dynamo may result from an increase in convective velocities caused by the formation of dense crystals at the CMB or turbulence caused by the settling of the crystals themselves.

To investigate these possibilities, we employ analogue tank experiments to explore the possible mechanisms driving convection during inward asteroid core crystallisation. An ammonium chloride solution is cooled from above with a layer of buoyant propanol separating the solution from the cold plate to prevent the growth of crystals on this boundary. Instead, the crystals form below the buoyant layer in a ‘snow zone’. We vary the temperature difference across this buoyant layer to investigate the different regimes that may exist. At each driving temperature difference, we measure the velocity fields of any fluid flow within the ammonium chloride solution using particle imaging velocimetry. This enables us to compare the convective velocities with and without crystallisation as well as develop scaling laws to apply the results of these experiments to models of core thermal evolution.

We find that the mean convective speeds increase by over an order of magnitude when the fluid is crystallising. This increase in speed is driven by an increase in the bulk density of the fluid in the snow zone due to the presence of a small crystal fraction. While the motion of crystals themselves do not induce any turbulence in the fluid due to their small size, they act to locally increase the density of the fluid, causing dense, crystal-rich plumes to emanate from the snow zone, which drive faster convective speeds throughout the fluid. This result provides a new mechanism for dynamo generation in inwardly crystallising cores, especially if remelting of falling iron crystals is delayed until deep within the core’s interior, as has recently been proposed for Mars, or if there is a nucleation barrier that causes significant undercooling before the onset of crystallisation. We also measure the temperature and composition as a function of depth within the tank, from which we may assess whether thermal equilibrium can be assumed when modelling snow zones in cores.

How to cite: Dodds, K., Bryson, J., Neufeld, J., and Harrison, R.: Exploring the dynamics of inward core solidification using analogue tank experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11668, https://doi.org/10.5194/egusphere-egu22-11668, 2022.

Earth-based measurements of Mercury's libration amplitude have been used previously to establish the existence of Mercury's liquid core and to estimate its size. However these previous works have not yet taken into account the internal core flows that can be induced by rotational variations such as librations. In the present study, we use a numerical linear model to investigate the effect that these internal flows might have on Mercury's libration amplitude and other observables. In particular we find that the inclusion of a stably stratified layer at the top of the core – the existence of which has been suggested by thermal evolution and numerical dynamo models – in most cases prohibits the transmission of any motion from the top of the core to its deeper parts and vice versa.

How to cite: Seuren, F., Triana, S. A., Rekier, J., Van Hoolst, T., and Dehant, V.: The influence of a stratified core on Mercury's librations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12178, https://doi.org/10.5194/egusphere-egu22-12178, 2022.

Generation and reversal of the Earth’s magnetic field have remained one of the most controversial topics.  It is well known that the Earth’s magnetic field is generated by dynamo action in the liquid iron outer core. This mechanism explains how a rotating, convecting, and electrically conducting fluid sustains a magnetic field.

In this study, we investigate the kinematic dynamo action associated with the well-known ABC-flow (see Dombre et al. [1986]). We focus on the “A = B = C = 1. Its dynamo properties have been assessed in 1981 by Arnold et al. [1981]. It belongs to fast dynamo action: a flow which achieves exponential magnetic field amplification over a typical time related to the advective timescale and not the ohmic diffusive timescale (in which case it is referred to as a “slow dynamo”).

We use DNS method for solving the kinematic dynamo problem, for which a solenoidal magnetic field evolution is governed under a prescribed flow by the induction equation.

In this work, we propose a deep learning method to solve the inverse dynamo problem by estimating the velocity field from the magnetic field. We train our deep learning algorithm from the velocity field and the magnetic field values obtained from the above flow model. Once the algorithm parameters are trained, the optimized algorithm is tested for the velocity field estimation from magnetic field. 

How to cite: Mouhali, W., Jun, J.-Y., and Lehner, T.: Velocity field reconstruction by Machine Learning during kinematic dynamo process, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13478, https://doi.org/10.5194/egusphere-egu22-13478, 2022.

Martian gullies are alcove-channel-fan systems that have been hypothesized to be formed by the action of liquid water and brines, the effects of sublimating CO₂ ice, or a combination of these processes. Recent activity and new flow deposits in these systems have shifted the leading hypothesis from water-based flows to CO₂-driven flows, as it is hard to reconcile present activity with the low availability of atmospheric water under present Martian conditions. Direct observations of flows driven by metastable CO₂ on the surface of Mars are however nonexistent, and our knowledge of CO₂-driven flows under Martian conditions remains limited. For the first time, we produced CO₂-driven granular flows in a small-scale flume under Martian atmospheric conditions in the Mars Chamber at the Open University (UK). The experiments were used to quantify the slope threshold and CO₂ fraction limits for fluidization. With these experiments, we show that the sublimation of CO₂ can fluidize sediment and sustain granular flows under Martian atmospheric conditions, and even transport sediment with grain sizes equal to half the flow depth. The morphology of the deposits is lobate and depends highly on the CO₂-sediment ratio, sediment grain size, and flume angle. The gas-driven granular flows are sustained under low (<20º) flume angles and small volumes of CO₂ (around 5% of the entire flow). Pilot experiments with sediment flowing over a layer of CO2 suggest that even smaller percentages of CO₂ ice are needed for fluidization. The data further shows that the flow dynamics are complex with surging behavior and complex pressure distribution in the flow, through time and space.

How to cite: Roelofs, L., Conway, S., Sylvest, M., Patel, M., McElwaine, J., Kleinhans, M., and de Haas, T.: Experimental CO2-driven granular flows under Martian atmospheric conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-679, https://doi.org/10.5194/egusphere-egu22-679, 2022.

    Since entering the 21st century, with the progress and development of science and technology. Human exploration of the world is not limited to the earth. Remarkable achievements have also been made in the exploration and understanding of the planet. In the last century, the US completed the exploration of the internal structure of the moon by using seismological methods through the Apollo program. The successful launch of insight in 2018 marked the birth of Marsquake, and realized the preliminary exploration of the internal structure of Mars. Due to the limitation of aerospace capability, the scientific research equipment we can carry is limited. The NASA spent hundreds of millions of dollars to deploy a seismograph on Mars. However, the deployment of a single seismograph is usually difficult to accurately measure the internal structure of Mars. Because the imaging method based on the internal vibration signal of Mars requires the use of a single seismograph constraining the source information and the internal structure of Mars at the same time, Which will increase the risk of inversion multiplicity.

    The main function of placing seismometers on the planet is to monitor the internal activity law of the planet. However, if we can obtain more reliable planetary exploration data without increasing the detection cost by designing a reasonable observation system, it will play an important role in the future exploration of the internal structure of the planet.

    Thus, a single station observation system is designed, which lays a foundation for seismic imaging to obtain more controllable and reliable data through the combination of single station and moving source(Rover). In this way, we can obtain two-dimensional and three-dimensional planetary seismic profiles in the future.

How to cite: Li, C. and Chen, X.: One station observation system for Mars exploration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-982, https://doi.org/10.5194/egusphere-egu22-982, 2022.

The Atmospheric Chemistry Suite (ACS) MIR channel onboard the ESA-Roscosmos Trace Gas Orbiter (TGO) (Korablev et al., 2018, 2019) probes the Martian atmosphere in the 2.3 – 4.2 µm spectral range using the Solar Occultation technique. ACS-MIR has now provided infrared observations of the Martian atmosphere over more than one and a half regular Martian Year since the end of the 2018/MY34 Global Dust Storm (GDS).

We analyzed this ACS-MIR dataset to detect the presence of water ice particles in the Martian atmosphere and retrieve their size from the 3 μm atmospheric absorption signature. Each observation results in a vertical profile of ice particle size within the cloud layer, with a vertical resolution of a few kilometers. The temporal and spatial sampling provided by the 2-hour period of TGO’s orbit allows us to observe the seasonal and latitudinal trends of the water ice clouds, with variations of about 20 to 40 km of the cloud’s altitude.

The method was first applied solely to the 2018/MY34 GDS year (Stcherbinine et al., 2020). This first study notably revealed the presence of small-grained clouds at very high altitudes (above 100 km) at the onset of the MY34 GDS, along with the presence of large water ice particles (r_eff > 1.5 µm) up to 65 km during the storm.

Data acquired during MY35, where no GDS occurred, provides a reference to be compared with the observations obtained during the MY34 GDS. We observe that the maximum altitude of the water ice clouds increases by about 10 km during the GDS compared to a nominal year, which suggests that the GDS significantly impacts water ice cloud distribution.

How to cite: Stcherbinine, A., Montmessin, F., Vincendon, M., Wolff, M., Korablev, O., Fedorova, A., Trokhimovskiy, A., Lacombe, G., Baggio, L., Irbah, A., and Braude, A.: Monitoring of Martian water ice clouds over one Martian Year with TGO/ACS-MIR, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1114, https://doi.org/10.5194/egusphere-egu22-1114, 2022.

A search for water on Mars is an important part of a space program. Water is likely to be contained not only in the polar caps but also deposited further away from the polar regions, specifically in the so called “fretted terrain” (near dichotomy boundary between the lowlands and highlands), in the northern lowlands, and elsewhere.  Here we attempt to reconstruct a northern paleo-ocean, using the gravity aspects and locations of features of the fretted terrain as constraints for paleo-seashore. Valles Marineris would contain water that would flow into this ocean. We use recent data on the gravity and magnetic fields of Mars and create from them the gravity aspects and magnetic field proxies computed from the recent gravity and magnetic models JGMRO_120F (Konopliv et al., 2020) and (Connerney et al., 2005; Langlais et al., 2019). We discovered that Isidis, based on gravity aspects, has many volcano-like characteristics despite the traditional view of this structure being an impact related. We note asymmetric positions of Martian polar caps that seem to be related to the magnetic field distribution and we propose a new hypothesis that polar cap accumulation relates to a plasmasphere interaction with the solar wind.  Analysis of the detection of direction of the impactor arrival for Hellas impact basin along with the gravity aspects (namely the strike angles) suggested  that not only the impact likely generated a reset of the global plum activity (that changed the overall unicellular convection pattern into the bicellular convection) but also note the possibility that the magnetic maxima in the polar region could be paleoindicators of the offset by this impact event so that the rotational poles have an offset from the magnetic poles.

How to cite: Klokocnik, J., Kletetschka, G., Kostelecky, J., Bezdek, A., and Karimi, K.: Gravity and magnetic fields of Mars - new findings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1708, https://doi.org/10.5194/egusphere-egu22-1708, 2022.

Wind driven dust resuspension is actively and ubiquitously observed at the surface of Mars, however the mechanisms involved, and conditions required are poorly understood (Neakrase et al., 2016). The objective of this laboratory study is to investigate various dust resuspension mechanisms using a unique set of recirculating environmental wind tunnel facilities at Aarhus University (Holstein-Rathlou et al., 2014). This study employs various sensor techniques including digital microscopy and optical reflectance to quantify dust removal as well as Laser Doppler Velocimetry and optical opacity measurement for determining dust concentration (Jakobsen et al., 2019). Importantly in these studies the dust was deposited from suspension within an environmental wind tunnel (Merrison et al., 2008).

Already from preliminary experiments significant advancements in our knowledge of dust resuspension have been made. Specifically, for the first time under Martian conditions direct wind driven dust remobilization has been observed (Rondeau et al., 2015). As expected, the process involved dust aggregate detachment and transport. Also for the first time saltation induced dust resuspension has been recreated (i.e. impact induced dust resuspension) from a loose sand bed coated with dust. Interestingly preliminary estimates have shown that both of these mechanisms appear to have similar values of threshold shear stress of around 0.07Pa, this is close to the expected threshold for saltation (Andreotti et al., 2021). It is hoped that both the resuspension flux and threshold can be quantified.

These studies are part of an international EU supported research project called ROADMAP (https://roadmap.aeronomie.be/). Three Mars analogue dust prototypes ‘are being used in these experiments. These have been developed and characterized by the ROADMAP team.

Acknowledgments

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004052.

References

Andreotti, B., Claudin, P., Iversen, J. J., Merrison, J. P., and Rasmussen, K. R.: A lower-than-expected saltation threshold at Martian pressure and below, Proceedings of the National Academy of Sciences, 118, 2021.

Holstein-Rathlou, C., Merrison, J., Iversen, J., Jakobsen, A., Nicolajsen, R., Nørnberg, P., Rasmussen, K., Merlone, A., Lopardo, G., and Hudson, T.: An environmental wind tunnel facility for testing meteorological sensor systems, Journal of atmospheric and oceanic technology, 31, 447-457, 2014.

Jakobsen, A. B., Merrison, J., and Iversen, J. J.: Laboratory study of aerosol settling velocities using laser Doppler velocimetry, Journal of Aerosol Science, 135, 58-71, 2019.

Merrison, J. P., Bechtold, H., Gunnlaugsson, H., Jensen, A., Kinch, K., Nornberg, P., and Rasmussen, K.: An environmental simulation wind tunnel for studying Aeolian transport on mars, Planetary and Space Science, 56, 426-437, 2008.

Neakrase, L., Balme, M., Esposito, F., Kelling, T., Klose, M., Kok, J., Marticorena, B., Merrison, J., Patel, M., and Wurm, G.: Particle lifting processes in dust devils, Space Science Reviews, 203, 347-376, 2016.

Rondeau, A., Merrison, J., Iversen, J. J., Peillon, S., Sabroux, J.-C., Lemaitre, P., Gensdarmes, F., and Chassefière, E.: First experimental results of particle re-suspension in a low pressure wind tunnel applied to the issue of dust in fusion reactors, Fusion Engineering and Design, 98, 2210-2213, 2015.

How to cite: Waza, A. A., Merrison, J. P., Iversen, J. J., and Rasmussen, K. R.: Laboratory study of dust resuspension mechanisms in the Martian Environment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3094, https://doi.org/10.5194/egusphere-egu22-3094, 2022.

We study a young (~ 4.5 Ma), 3.4 km long landslide located in the floor of Simud Vallis, a large outflow channel that together with Tiu Vallis once connected the Valles Marineris with the Chryse Planitia on Mars (1). Multiple teardrop-shaped islands are present on Simud Vallis’ floor, all elongated in the S–N direction of the flow (2) that incised the Mid-Noachian plateau (3). The Simud Vallis (SV) landslide is located on the western side of one of such landforms. It is characterized by numerous boulders on its deposits (4). By making use of the 2 m-scale HiRISE DEM of (4) we reconstruct the terrain surface before the SV landslide. We thereby estimate the release and deposition heights and volumes related to the rotational slide of the landslide, called stage 1, and of the subsequent flow, called stage 2. Using the r.avaflow software (5) we simulate the mass movement of stage 2 and obtain simulated deposits that are comparable to the current landslide deposit in terms of both horizontal extent and thickness (6). Through two 0.25 m-scale HiRISE images we identify and manually count >130,000 boulders that are located along the landslide, deriving their size-frequency distribution and spatial density per unit area for boulders with an equivalent diameter ≥1.75 m. Our analyses (6) shows that the distribution is of a Weibull-type (7), which commonly results from sequential fragmentation and it is often used to describe the particle distribution derived from grinding experiments (8,9). This suggests that the rocky constituents of the SV landslide fractured and fragmented progressively during the course of the mass movement, consistent with our proposed two-stage model of landslide motion.

References:

 (1) Pajola, M. et al., 2016. Icarus, 268, 355. (2) Carr, M.H. & Clow, G.D., 1981. Icarus, 48 (1), 91. (3) Tanaka, K.L. et al., 2014. US Geological Survey. (4) Guimpier, A., et al., 2021. PSS, 206, 105303. (5) Mergili, M., et al., 2017. Geosci. Model Dev. 10, 553. (6) Pajola, M. et al., 2022. Icarus, 375, 114850. (7) Weibull, W., 1951. J. Appl. Mech., 18, 837. (8) Brown, W.K. & Wohletz, K.H., 1995. J. Appl. Phys. 78, 2758. (9) Turcotte, D.L., 1997. Cambridge University Press, Cambridge.

How to cite: Pajola, M., Mergili, M., Cambianica, P., Lucchetti, A., Brunetti, M. T., Guimpier, A., Mastropietro, M., Munaretto, G., Conway, S., Beccarelli, J., and Cremonese, G.: Mass movement reconstruction and boulder size-frequency distribution of the Simud Vallis landslide, Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3118, https://doi.org/10.5194/egusphere-egu22-3118, 2022.

Passive radar sounding has been proposed as a low-cost, low-risk way to enrich the scientific return of planetary radar sounders, especially in the vicinity of bright radio sources such as Jupiter [Romero-Wolf et al. (2015), Icarus, 248:463-477], whose moons will be studied by radar sounders in the late 2020's and 2030's. To predict what passive radargrams may look like as a function of parameters such as the noise source spectrum and the surface/subsurface roughness, analytical and empirical models have been proposed in the literature [Schroeder et al. (2016), PSS, 134:52-60], and proof-of-concept hardware has been tested on Earth [Peters et al. (2018), TGRS, 56(12) 7338-7349]. To cement our understanding of passive sounding, we searched for traces of passively-acquired radar echoes in existing SHARAD radargrams. Such signals can be uncovered if the incoming noise was captured in one acquisition and its reflection by surface or subsurface features in the next one. Cross-correlating the two uncompressed rangelines could then reveal possible present Martian features using only the signals of opportunity. We started from the engineering parameters of SHARAD, such as its orbit, Rx window length, and PRF, to work out all the geometric configurations where Jovian emissions and their reflection from the surface could have been intercepted if such emissions were present. We made the assumption that waves must be specularly-reflected off the surface of Mars at a given angle, and looked for the angles at which the delay of the reflected noise matches the PRI of SHARAD. We have determined that, for the range of altitudes SHARAD operates at, the (Jupiter-Mars, Mars-SHARAD) angle must lie between 35° and 52°. Based on Friis-like arguments, we believe the SNR of such signals could reach 10 dB in the case of a smooth surface such as Elysium Planitia. We then cross-correlated this database of SHARAD radargrams with that of a model of Jovian noise occurrence at Mars using ExPRES [Hess et al. (2008), GRL, 35.13], and extracted a list of potential candidates. Preliminary analysis of these candidates shows that some of them may indeed contain passively-acquired signals that may be exploited scientifically. We have additionally conducted passive Stratton-Chu simulations [Gerekos et al. (2019), TGRS, 58(4) 2250-2265] of these cases to support interpretation.

How to cite: Gerekos, C., Steinbrügge, G., Donini, E., and Romero-Wolf, A.: Exploitation of SHARAD data from a passive sounding perspective: a preliminary analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3191, https://doi.org/10.5194/egusphere-egu22-3191, 2022.

To accurately simulate the climate and the fate of volatiles for thousands to millions of years we must couple physical processes with very different timescale, ranging from clouds microphysics and atmospheric dynamics (represented in the GCM) to the evolution of lakes, glacier accumulation, and subsurface ice evolution.

Given the diversity and the complexity of the Martian paleoclimates, we choose to use use an ambitious “asynchronous coupling” between the slow ice and water reservoirs models and the GCM.

In practice our innovative Mars evolution model will use a horizontal grid identical to that of the GCM, and include the same representation of the micro-climate on slopes. In our case, we will run the Mars Evolution Model with a timestep of 50 to ~500 years, depending upon the dynamics of the modeled system (smaller timesteps must first be used so that the different volatile reservoirs reach a quasi-equilibrium, then the timestep will depends on the evolution of the forcing, which is slow in the case of obliquity, for instance) . At each timestep, the inputs from the atmosphere (e.g. mean precipitation, sublimation and evaporation, temperatures, dust deposition) will be obtained through a multi-annual run of the Global Climate model using the outcome of the Mars Evolution Model as initial state.

First results about evolution of water ice and CO2 ice glacier will be presented.

How to cite: Vandemeulebrouck, R., Forget, F., Lange, L., Millour, E., Delavois, A., Bierjon, A., Naar, J., and Spiga, A.: Simulating long term climate variation with a planetary evolution model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3635, https://doi.org/10.5194/egusphere-egu22-3635, 2022.

In some high latitude craters, intriguing moraines are interpreted to have been deposited by CO₂ ice glaciers, essentially frozen from when the local climate was colder (i.e., when Mars obliquity was low) [1]. This scenario has been little studied, but it suggests that the atmosphere could totally collapse into CO₂  glaciers, leaving behind a residual atmosphere of only Ar and N₂, but 20 times less dense than today [2]. 

However, these results are based on a radiative equilibrium that does not take into account all the dynamics of the atmosphere.  Such periods of low obliquities generally last tens of thousands of years [3], making a complete simulation with a classical Global Circulation Model impossible.  

We will present the preliminary results of our climate simulations of Mars at low obliquity based on our new tool which is the Planetary Evolution Model developed at the LMD (Fig 1.). This model allows us to simulate the evolution of the climate, based on the LMD GCM, over long-time steps. Particular attention will be paid to the condensation of the atmosphere in the form of CO₂  glaciers, and to the composition of the residual atmosphere.

Fig 1. Principles of the Planetary Evolution Model 

References: 
[1] Kreslavsky and Head, Carbon dioxide glaciers on Mars: Products of recent low obliquity epochs(?). Icarus, 216:111–115, 2011.
[2] Kreslavsky and Head. Mars at very low obliquity: Atmospheric collapse and the fate of volatiles. Geophysical Research Letters, 32(L12202), 2005.

[3] Laskar, Correia, Gastineau, Joutel, Levrard, Robutel, Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343–364, 2004.

Acknowledgments:
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No 835275).

How to cite: Lange, L., Forget, F., Vandemeulebrouck, R., Millour, E., Delavois, A., Naar, J., Spiga, A., Bierjon, A., and Dupont, E.: Climate Simulations of Mars at Low Obliquity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3651, https://doi.org/10.5194/egusphere-egu22-3651, 2022.

The Emirates Mars Mission (EMM) – Hope Probe – has commenced its one-Martian-year science phase on May 23rd 2021. The goals of the mission aim to understand the Martian atmosphere, its processes, dynamics, and circulation using three scientific instruments observing Mars' different atmospheric layers simultaneously. 

Hope Probe is studying the lower atmosphere of Mars using the Emirates eXploration Imager (EXI) and the Emirates Mars Infrared Spectrometer (EMIRS). While EXI measures the distribution of water ice and ozone using ultraviolet bands, EMIRS measures the optical depth of dust, ice clouds and water vapor in the atmosphere, in addition to the temperature of the surface and the atmosphere using infrared bands. On the other hand, the Emirates Mars Ultraviolet Spectrometer (EMUS) is studying the upper atmosphere of Mars through extreme and far ultraviolet bands to measure the distribution of carbon monoxide and oxygen in the thermosphere, and oxygen and hydrogen in the exosphere of Mars.

The scientific observations are taken from a unique high-altitude orbit with dimension 20,000 x 43,000 km that offers unprecedented local and seasonal time coverage over most of the planet. This presentation will highlight key atmospheric and surface results from the Hope Probe since it started collecting scientific data on the Martian atmosphere upon arrival to Mars on February 9th 2021. The data returned from the mission is enabling us to improve our understanding of the weather circulation in the lower atmosphere, the mechanisms behind the upward transport of energy and particles, and the subsequent escape of atmospheric particles from the gravity of Mars.

How to cite: Almatroushi, H., Deighan, J., Edwards, C., Holsclaw, G., and Wolff, M. and the EMM Science Team: Results from the Emirates Mars Mission (EMM) - Hope Probe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3727, https://doi.org/10.5194/egusphere-egu22-3727, 2022.

The Mars Moon eXploration (MMX) mission by the Japan Aerospace Exploration Agency, JAXA, which is going to explore the Martian Moons Phobos and Deimos and also return samples from Phobos back to Earth will also deliver a small (about 25 kg) Rover to the surface of Phobos.

The payload of this rover consists of a Raman spectrometer (RAX) to measure the mineralogical composition of the surface material, a stereo pair of cameras looking affront (NavCam, also used for navigation) to provide the properties of the investigated area, a radiometer (miniRAD) to measure the surface brightness temperature and determine thermal properties of both regolith and rocks, and two cameras looking at the wheel-surface interface (WheelCam) to investigate the properties and dynamics of the regolith. The cameras will, thus, serve for both, technological and scientific needs.
After the Rover has been delivered by the main spacecraft, it shall upright itself and operate for about 100 days on the surface of Phobos to investigate terrain and mineralogy along its path.
The measurements are going to provide ground truth by studying in-situ properties such as the physical properties and heterogeneity of the surface material.

MMX is planned to be launched in September 2024, the Rover delivery is currently planned for 2027.
The Rover is a contribution by the Centre National d’Etudes Spatiales (CNES) and the German Aerospace Center (DLR) with additional contributions from INTA (Spain) and JAXA.

How to cite: Ulamec, S., Michel, P., Grott, M., Böttger, U., Hübers, H.-W., Cho, Y., Rull, F., Murdoch, N., Vernazza, P., Biele, J., Tardivel, S., and Miyamoto, H.: Phobos Surface Science with the MMX Rover, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4033, https://doi.org/10.5194/egusphere-egu22-4033, 2022.

Thermal tides are planetary-scale harmonic responses driven by diurnal solar forcing and influenced by planetary topography. Excited by solar heating absorbed by the atmosphere and energy exchange with surface, thermal tides grow in Martian atmosphere. These tides usually have large amplitudes due to the low heat capacity of Martian atmosphere, and dominate its diurnal variations. In this talk, we present results of the analysis of thermal tides in Martian atmosphere using temperature profiles retrieved using infrared spectra obtained by the Emirates Mars InfraRed Spectrometer (EMIRS) instrument onboard the Emirates Mars Mission (EMM) Hope spacecraft. The first set of data obtained during the mission science phase is selected, covering a solar longitude (L_S) range 60° - 80° of Martian Year (MY) 36, which is a clear season without large dust storms. The novel orbit design of the spacecraft allows a full local time coverage to be reached within 10 Martian days, approximately ~5° of L_S. It enables the analysis of diurnal temperature variations without the interference of seasonal changes, which was shown to be significant in previous studies. Wave mode decomposition is also applied to these diurnal variations, and amplitudes of other tide modes are derived. The results show good agreements with predictions derived using the Laboratoire de Météorologie Dynamique (LMD) Mars Global Circulation Model (GCM), except for a noticeable phase difference of the dominant diurnal thermal tide. This work provides valuable information on understanding diurnal variations in Martian atmosphere and inspires future advances of Mars GCMs.

How to cite: Fan, S., Forget, F., Smith, M., Guerlet, S., Badri, K., Atwood, S., Edwards, C., Christensen, P., Deighan, J., Al Matroushi, H., Bierjon, A., Liu, J., and Millour, E.: Thermal tides in Martian atmosphere observed by EMIRS onboard the Hope spacecraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4208, https://doi.org/10.5194/egusphere-egu22-4208, 2022.

Through today's observation of dry lakes, rives and large valley networks, we can assume liquid water abundantly flowed on Mars during the Noachian era, approximatively 4Gya. However, the climate that host this active water cycle is yet poorly understood. Recent modeling studies tried to reproduce the conditions that may have occured on the planet, trying to find an atmospheric process or composition that could solve the well known Faint Young Sun Paradox. Theses modeling studies, through the use of 3-dimensional Global Climate Models struggled to warm sufficiently the past climate of Mars, even considering different greenhouse gases, the role of clouds, meteoritic impact or even volcanism. However, the presence of H₂ could be an interesting solution for a sustainable warming as some recent studies suggest (Turbet and Forget, 2021). Another recent study (Ito et al. 2020) suggested that H₂O₂ might be a convincing candidate but has to be in high supersaturation ratio in the atmosphere, even though it only used a simplified 1D model and relatively high supersaturation levels.

We try here to explore the scenario of supersaturated water, that might be a specy able to provide a sufficient global warming under supersaturated conditions or through the formation of high altitude clouds.  Through 1D and 3D modeling, we try to constrain the theoritical supersaturation level of H₂O that will allow the warming of the climate above 273K. Our results suggest that in an atmosphere only composed of CO₂ and H₂O, water supersaturation can create a significant warming but only with with supersaturation levels in the lower layers of the atmosphere, although it can be seen as unrealistic. We describe in this work the effect of supersaturation on temperatures, clouds, and the water cycle of the simulated planet. Even if we do not tackle the question whether the supersaturation hypothesis is realistic or not, these results give a better understanding of what would be Early Mars' climate under such conditions.

How to cite: Delavois, A., Forget, F., Turbet, M., Millour, E., Vandemeulebrouck, R., Lange, L., and Bierjon, A.: Water supersaturation modeling for Early Mars Climate during Noachian, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4517, https://doi.org/10.5194/egusphere-egu22-4517, 2022.

The EXI instrument is a camera onboard the EMM spacecraft, with a field a view capable capturing the full disk of Mars throughout its nominal science orbit.   Though the use of its multiple band passes (220, 260, 320, 437, 546, 635 nm) and the effective spatial resolution (2–4 km per native pixel), EXI’s primary goal is to provide both regional and global imaging of the Martian atmosphere with diurnal sampling over much of the planet on a time scale of approximately 10 days.  This presentation will provide an overview of EXI’s on-orbit instrument performance, a brief description of the observation strategy employed with the start of Science Operations (23-May-2021, Ls=49°), and the retrieval results of the ice optical depth and their diurnal behavior for the period of mid-spring through late-summer in the northern hemisphere.  More specifically, the presentation will cover:

• Status of the instrument calibration and plans for on-going on-orbit monitoring of instrument performance, including radiometric errors. Plus, some guidance on interpreting the metadata of the EXI publicly released raw and calibrated images;

• Illustration of the various disk geometries sampled during an EMM orbit of Mars, and how such observations are combined to provide diurnal coverage of the illuminated portion of the disk/atmosphere;

• Overview of the ice optical depth retrieval algorithm, and its application to the data obtained since the start Science Operations with an emphasis on the behavior of the aphelion cloud belt; including the formation and decay phases.

How to cite: Wolff, M., Jones, A. R., Osterloo, M., Shuping, R., Edwards, C., Al Shamsi, M., Espejo, J., Fisher, C., Jeppesen, C., and Knavel, J.: The Emirates eXploration Imager (EXI) onboard the Emirates Mars Mission (EMM): Overview of In-flight Performance, and Water Ice Cloud Retrievals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4991, https://doi.org/10.5194/egusphere-egu22-4991, 2022.

Raman spectroscopy is an excellent tool for the detection and discrimination of biomolecules e.g. pigments. The highest relevance of Raman spectroscopy in astrobiology has been well-established. The miniaturized, dedicated Raman spectrometers are currently a part of the experimental payload within rovers in the frame of Martian missions Mars 2020 (NASA) and ExoMars (ESA). Finding biomolecules in the rocky environments (for example, detecting carotenoids) would be an amazing outcome of Mars missions. On Earth, semi-translucent or translucent minerals such as gypsum are ideal habitats for endoliths, especially phototrophs. The mineral environment participates in protecting them against harsh superficial environments. Cyanobacteria colonize gypsum, halite, ignimbrite in the Atacama extremely dry zones with high UV flux. Pigments of endoliths encountered there and detected using Raman spectroscopy include mainly UV-screening pigments such as carotenoids and scytonemin. Selenitic gypsum outcrops of Messinian age commonly harbour cyanobacteria and algae also in less harsh environments: in Sicily (annual precipitation 400-600 mm) [1], Poland (600 mm) and Northern Israel (400 mm). Details on the distribution of pigments (including scytonemin) from several gypsum sites in southern Sicily and eastern Poland are presented [2]. Raman investigations using 780, 532 and 445 nm lasers show more detail on the distribution of UV-screening pigments in the dark zones. These dark zones are colonized dominantly by cyanobacteria, mostly by black-bluish Gloeocapsa compacta and yellow-brown Nostoc sp. Raman analysis allows to discriminate between these cyanobacterial taxa. Raman bands of scytonemin at 1593, 1552, 1438 and 1173 cm^-1 were detected in colonies of Nostoc sp. Gloeocapsin, a pigment specific for Gloeocapsa sp, shows characteristic Raman bands similar to anthraquinone-based parietin of lichens: at 1665, 1575, 1378, 1310 and 465 cm^-1 [2]. Both pigments can be used as biomarkers in geobiological and astrobiological studies. Other photosynthetic and protective pigments were also detected: carotenoids, chlorophylls and phycobiliproteins. Deciphering the presence of biomolecules (including pigments) using Raman spectroscopy helps to understand endoliths. Deploying miniature Raman spectrometers at terrestrial Mars analogue localities as well as in depth investigations of colonised gypsum through laboratory microspectrometric investigations is of the highest relevance for the current Martian missions.

References

[1] J. Jehlička, A. Culka, J. Mareš, (2019) Raman spectroscopic screening of cyanobacterial chasmoliths from crystalline gypsum—The Messinian crisis sediments from Southern Sicily, Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy 51, 1802-1812. [2] K. Němečková, A. Culka, I. Němec, H.G.M. Edwards, J. Mareš, J. Jehlička (2021) Raman spectroscopic search for scytonemin and gloeocapsin in endolithic colonisations in large gypsum crystals. Journal of  Raman Spectroscopy 52, 2633-2647.

How to cite: Jehlicka, J., Němečková, K., and Culka, A.: Detecting Raman spectra of pigments from gypsum endoliths: is this a useful training for Martian missions?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5120, https://doi.org/10.5194/egusphere-egu22-5120, 2022.

We report the analysis of pressure measurements at Jezero crater, Mars by the MEDA instrument [1] onboard the rover Perseverance following its landing and covering the period from March 5, 2021 up to this meeting presentation (approximately from solar longitudes 15° to 200°). We identify a variety of atmospheric phenomena, spanning from local to global spatial and temporal scales that leave their imprint in the pressure data [2]. These comprises: Local turbulence (high frequency fluctuations), waves (short period oscillations 12-24 minutes), local vortices (sudden pressure drops from seconds to a minute), baroclinic waves (oscillation periods 4-5 sols) and up to six Fourier components of the thermal tides. The normalized amplitude of the diurnal and semidiurnal tides show a large variability along the studied period, but smaller changes are also noted in tidal components 3 to 6.  We report on the effects of the presence of water ice clouds and dust from storms on the tidal components. Finally, we present the main parameters that characterize each of the phenomena studied, their variability throughout this period, and a preliminary interpretation for all of them.

References:

[1] Rodríguez-Manfredi J. A. et al., Space Sci. Rev., 217.3, 1-86 (2021)

[2] Sánchez-Lavega A. et al., Perseverance/Mars2020 measurements of the daily pressure cycle at Jezero, P25A-03, AGU Fall Meeting (2021)

How to cite: Sanchez-Lavega, A., del Rio-Gaztelurrutia, T., Hueso, R., de la Torre, M., Harri, A.-M., Genzer, M., Hieta, M., Polkko, J., Rodríguez-Manfredi, J. A., Tamppari, L. K., Newman, C., Munguira, A., Martínez, G., Vicente-Retortillo, A., Lemmon, M., Pla-Garcia, J., Guzewich, S., Toledo, D., Apéstigue, V., and Viúdez-Moreiras, D. and the Additional Team members: Weather at Jezero, Mars from pressure measurements by the rover Perseverance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5796, https://doi.org/10.5194/egusphere-egu22-5796, 2022.

On February 18, 2021, NASA’s Mars 2020 Perseverance rover landed successfully in Jezero crater. Several geological and compositional units were previously identified from orbital data analysis : a dark pyroxene-bearing floor unit; an olivine-bearing unit exposed in erosional windows and partially altered into phyllosilicates and carbonates ; a deltaic complex and its possible erosional remnants and a marginal carbonate-bearing unit. As of Sol 300 (December 2021), the rover has visited two geological units in situ: the dark pyroxene-bearing floor unit and the olivine-bearing floor unit. Others investigations of geological units of interest have been carried out using long distance (up to several kilometers) observations.

The SuperCam instrument contains a suite of techniques including passive spectroscopy in the 0.40-0.85 (VIS) and 1.3-2.6 microns (IR) wavelength ranges, and a color camera (RMI- Remote Micro-Imager) providing high resolution context images. Since the landing, SuperCam has acquired thousands of VISIR spectra of nearby rocks (including both natural and abraded surfaces), as well as hundreds of spectra of distant targets (from 10s of m to 20 km). The VISIR field of view of each individual spectrum ranges from a few mm for the rock of the workspace to 20 m to 20 km. The aim of this contribution is to summarize the main results of VISIR spectra up to Sol 300.

The two geological units investigated in situ have distinct spectra. The crater floor rough unit (Cf-fr)  has a pervasive 1.9 µm absorption indicative of hydration. Additional absorption at 2.28 µm indicate the presence of iron-rich phyllosilicates. Correlations between 1.9 µm and 2.4 µm absorption bands or between 2.1 µm and 2.4 µm bands suggest the presence of both poly and monohydrated sulfates. Spectra similar to oxy-hydroxides have also been observed in some rocks. Unmixing methods such as factor analyses highlight a high calcium pyroxene component. To sum up, the Cf-fr is an altered pyroxene rich unit. The second unit investigated in situ is a region called Seitah, which is dominantly olivine-rich from orbital analyses. Supercam VISIR data confirm the strong signature of olivine of the unit and display a complex suite of absorptions in the 2.3 µm - 2.4 µm region suggesting the presence of iron and magnesium phyllosilicates and/or carbonates. The alteration signature seems to be associated with olivine grains. 

Distant observations were acquired on the western delta front, several remote mesas and hills, on Jezero floor unit (the unit on which Perseverance landed on and investigated in situ), on Seitah before being visited by the rover, and on even more distant targets such as the crater rim or the marginal carbonate-bearing unit. The observed spectral signatures form different clusters depending on the type of target, highlighting the spectral diversity of Jezero geological units.  Remarkably, the long distance observations of Seitah region are in perfect agreement with the in situ measurements confirming the relevance of long distance observations to assess the geological/mineralogical context of Perseverance’s future traverses.

How to cite: Quantin-Nataf, C., Mandon, L., Royer, C., Beck, P., Montmessin, F., Forni, O., Le Mouelic, S., Poulet, F., Johnson, J., Fouchet, T., Dehouck, E., Brown, A., Tarnas, J., Pilleri, P., Gasnault, O., Mangold, N., Maurice, S., and Wiens, R.: Infrared Reflectance of Jezero geological units from Supercam/Mars2020 Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5969, https://doi.org/10.5194/egusphere-egu22-5969, 2022.

The Mars 2020 Perseverance rover landed in Mars in February 2021 in Jezero crater at 18.4ºN. One of its instruments is MEDA, the Mars Environmental Dynamics Analyzer, which measures among other properties air pressure, air temperature at different levels, surface temperature from its infrared emission, and the presence of dust. The latter is provided by a set of photodiodes pointing in different directions that constitute the Remote Dust Sensor or RDS. MEDA data are acquired with a frequency of 1 or 2 Hz in data sessions that cover about 50% of a full sol allowing a full characterization of daily and seasonal cycles.

Predictions before landing indicated that Jezero should be a location favoring the formation of intense vortices and dust devils in Spring to Summer. These expectations were fulfilled with frequent observations of vortices and dust devils observed with MEDA and the rover cameras. A systematic analysis of MEDA’s pressure sensor shows the close passage of convective vortices. These are detected as events that range from short and sharp pressure drops to long and deep pressure drops. Wind measurements during the vortex passage, combined with their duration, give information about the size and distance of the vortex. Many of the most intense events in terms of the pressure drop and peak winds detected have simultaneous drops of light measured with the RDS and are dust devils equivalent to those observed at much higher distances with Perseverance cameras. The combination of pressure, wind and RDS measurements largely constrain the geometry effects associated to these close passing dust devils. Some of them also have additional clear counterparts in other MEDA sensors including temperatures, which allows for an in-depth investigation of the physical properties of selected dust devils. Some events might also be captured by the SuperCam microphone, that records pressure fluctuations in the audible domain. The acoustic signal can provide insights into the short term behavior of vortices, and can contribute to the determination of the vortex physical properties. Statistics of vortices allow us to determine the probability of finding these events with the SuperCam microphone.

We present results for over one Earth year (Ls=6; Feb. 2021, Northern Hemisphere Spring – Ls=180; Feb. 2022; Northern Autumn Equinox). We show the daily cycle of vortex and dust devil activity and how this has evolved from early Spring until the start of the dust storms season. We present results of the distribution of sizes of vortices and dust devils and a selection of some remarkable events. These include direct hits of dust devils passing right through Perseverance, tangential passes in which one wall of the vortex passes over Perseverance, and more distant passages of very dusty events whose diameter in some cases largely exceed 100 m. A comparison of the vortex convective activity observed at Jezero with results from a Large-Eddy-Simulations (LES) using the MarsWRF model helps us to gain insight into how the detected vortices and their properties can constrain other general properties of the atmospheric dynamics at Jezero crater.

How to cite: Hueso, R., Newman, C., Munguira, A., Sánchez-Lavega, A., Lemmon, M., del Río-Gaztelurrutia, T., Richardson, M., Apestigue, V., Toledo, D., Vicente-Retortillo, Á., de la Torre-Juarez, M., Rodríguez-Manfredi, J. A., Tamppari, L., Arruego, I., Murdoch, N., Martínez, G., Navarro, S., Gómez-Elvira, J., Baker, M., and Lorenz, R. and the Mars 2020 Atmosphere Team: Seasonal variation of vortex and dust devil activity on Jezero and physical characterization of selected events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6027, https://doi.org/10.5194/egusphere-egu22-6027, 2022.

The Emirates Mars Mission (EMM) Emirates Mars Infrared Spectrometer (EMIRS) currently around Mars is acquiring remote measurements of the martian surface (temperature and composition) and lower atmosphere. EMIRS is a FTIR spectrometer covering the range from 6.0-100 µm (1666-100 cm^‑1) with a spectral sampling as high as 5 cm^-1 with a 5.4-mrad IFOV. The EMIRS optical path includes a flat 45˚ pointing mirror to enable one degree of freedom while the spacecraft provides the other to build up a 2-dimensional array of observations. The primary goals of EMIRS are to characterize the geographic and diurnal variability of key atmospheric constituents (water ice, water vapor, and dust) along with temperature profiles and surface temperature on sub-seasonal timescales

EMIRS acquires data of the full martian disk and thus provides an integrated view of the martian surface and atmosphere in every spectrum. These observations include complete diurnal, seasonal, and geographic coverage of atmospheric properties, surface temperature, and also surface composition/mineralogy at wavelengths not regularly acquired of the martian surface. Due to the unique nature of the EMM orbit, EMIRS also collects data that spans the full local solar time range (all solar incidence angles), at multiple emission angles. These unique observations permit the interrogation of diurnal surface ices/frost, thermophysics (including sub-surface layering from both a seasonal and diurnal skin depth), surface roughness, and rock abundance in addition to the primary science goals.

In this presentation, we provide an overview of the first surface observations, atmospheric retrieval algorithm, and first atmospheric science results from the aphelion-season observations taken by EMIRS over the first several months of EMM Science Phase operations.

How to cite: Edwards, C., Smith, M., Atwood, S., Badri, K., Christensen, P., Wolff, M., Osterloo, M., Al Tunaiji, E., Al Mheiri, N., Yousuf, M., Wolfe, C., Smith, N., and Anwar, S.: The Atmosphere and Surface of Mars as Revealed by the Emirates Mars Infrared Spectrometer (EMIRS), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6039, https://doi.org/10.5194/egusphere-egu22-6039, 2022.

NASA’s Mars 2020 Perseverance rover landed in Jezero Crater (~18.4ºN, 77.6ºE) on February 2021 at L_s~5º, just after the northern spring equinox. Perseverance carries the Mars Environmental Dynamics Analyzer (MEDA) instrument [1], which includes a wind sensor that is a heritage from previous sensors sent to Mars as part of the Mars Science Laboratory (MSL) and InSight missions. Those sensors allowed the characterization of the near-surface wind patterns at Gale Crater [2] and Elysium Planitia [3,4]. The wind sensor of MEDA is allowing near-surface wind patterns to be characterized at Perseverance’s landing site, thus complementing the data acquired by previous missions on the surface of Mars.

Previous missions at different locations on the Martian surface observed a contribution by several mechanisms from different scales involved in the near-surface winds, including the effect of local and regional slope winds induced by topography, thermal tides, baroclinic waves and the Hadley cell, each one with a variable weight on the resulting wind patterns as a function of location, season and the presence of dust storms (e.g. [2-4] and references therein). The near-surface wind data acquired by Mars 2020 show a complex dynamics at Jezero Crater, as predicted by models (e.g. [5]). Preliminary interpretation suggests that the diurnal cycle of winds is dominated by the regional circulation mainly forced by slope winds in the Isidis basin region, which interact with the local scale circulation at Jezero and Hadley cell flows. The potential contribution by these mechanisms on the resulting wind patterns measured at Mars2020’s landing site will be presented, with a further focus on the observed wind variability supported by probabilistic models.

References:

[1] Rodriguez-Manfredi et al. (2021), SSR, 217(48). [2] Viúdez-Moreiras et al. (2019), Icarus, 319, 909-925. [3] Banfield et al. (2020), Nat.Geo, 13, 190-198. [4] Viúdez-Moreiras et al. (2020) JGR-Planets, 125, e2020JE006493. [5] Newman et al. (2021) SSR, 217(20).

How to cite: Viúdez-Moreiras, D., Newman, C. E., Gómez-Elvira, J., Harri, A.-M., Genzer, M., Tamppari, L., de la Torre, M., Sánchez, A., Hueso, R., Guzewich, S., Sullivan, R., Pla, J., Navarro, S., Munguira, A., Lorenz, R., Herkenhoff, K., Rodríguez-Manfredi, J. A., and MEDA team, T.: The near-surface wind patterns as observed by NASA Mars 2020 Mission at Jezero Crater, Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6325, https://doi.org/10.5194/egusphere-egu22-6325, 2022.

After 18 years in orbit Mars Express remains one of ESA’s most scientifically productive Solar System missions, with a publication record now exceeding 1450 papers. Characterization of the surface geology on a local-to-regional scale by HRSC, OMEGA and partner experiments on NASA spacecraft has allowed constraining land-forming processes in space and time. Recent studies characterized the geology of Jezero crater in great detail and provided Digital Elevation Model (DEM) of several equatorial regions at 50 m/px resolution. New maps and catalogues of surface minerals with 200 m/px resolution were released. MARSIS radar published new observations and analysis of the multiple subglacial water bodies underneath the Southern polar cap. Modelling suggested that the “ponds” can be composed of hypersaline perchlorate brines.

Spectrometers and imagers SPICAM, PFS, OMEGA, HRSC and VMC continue adding to the longest record of atmospheric parameters such as temperature, dust loading, water vapor and ozone abundance, water ice and CO₂ clouds distribution and observing transient phenomena. More than 27,000 ozone profiles derived from SPICAM UV spectra obtained in MY#26 through MY#28 were assimilated in the OpenMARS database. A new PFS “scan” mode of the spacecraft was designed and implemented to investigate diurnal variations of the atmospheric parameters. Observations of Tharsis region and Hellas basin contribute to mesoscale meteorology.

ASPERA measurements together with MAVEN “deep dip” data enabled assessment of the conditions that lead to the formation of the dayside ionopause in the regions with and without strong crustal magnetic fields suggesting that the ionopause occurs where the total ionospheric pressure (magnetic + thermal) equals the upstream solar wind dynamic pressure.

In 2021 Mars Express successfully performed two types of novel observations. In egress-only radio-occultations a two-way radio link was locked at a tangent altitude of about 50 km. This is well below the ionospheric peak and would allow perfect sounding of the entire ionosphere thus doubling the number of ionospheric soundings. MEX and TGO performed several test UHF occultations. The dual-spacecraft radio-occultation technique would allow much broader spatial distribution of the missions’ radio occultation profiles.  

Mars Express is extended till the end of 2022. A science case for the mission extension till the end of 2025 will be developed and submitted in March 2022. The talk will give the Mars Express status, review the recent science highlights, and outline future plans including synergistic science with TGO and other missions.

How to cite: Titov, D., Wilson, C., Bibring, J.-P., Cardesin, A., Carter, J., Duxbury, T., Forget, F., Giuranna, M., González-Galindo, F., Holmström, M., Jaumann, R., Määttänen, A., Martin, P., Montmessin, F., Orosei, R., Pätzold, M., Plaut, J., and Sgs Team, M.: Mars Express science highlights and future plans, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6333, https://doi.org/10.5194/egusphere-egu22-6333, 2022.

The Mars Environmental Dynamics Analyzer (MEDA) is a meteorological station onboard Mars 2020 that characterizes the near surface atmosphere. Among other sensors MEDA has 5 Air Temperature Sensors (ATS) at two altitudes: 0.85m, in the front of the rover, and 1.45m around the Remote Sensing Mast, which are azimuthally distributed so that at least one sensor is located upwind. This configuration ensures that, for most environmental conditions, the thermal contamination caused by the rover can be set apart. Local air temperatures are read with a frequency of 1 or 2 Hz, and ATS data can characterize timescales from atmospheric turbulence to the daily temperature cycle and its seasonal evolution. 

Here we show the daily temperature cycle at Jezero and an analysis of its seasonal evolution over the first half Martian year of the mission from Spring (Ls=6) to Autumn Equinox (Ls=180). Simultaneous ATS and winds from MEDA’s wind sensors show that, for most rover orientations, solar irradiation and winds clean environmental measurements are obtained at the 1.45m level. However, clean measurements at the 0.85m level are not always fully achieved, and a small residual thermal contamination is found at this level in many measurement sessions. The daily temperature cycle reflects the daily cycle of convection and turbulence. Strong and fast thermal oscillations start a few hours after sunrise, peak near noon, and collapse before sunset. The seasonal evolution shows a progressive increase of temperatures as summer advances, but less steep than what is retrieved at other Martian locations by previous missions. At the 0.85m level, changes in atmospheric temperatures with time-scales of a few sols correlate well with variations in local terrain properties. At the 1.45m level, similar temperature changes with timescales of a few sols are also found. We investigate whether these changes at 1.45m can be associated with changing atmospheric opacity due to dust and clouds, which are measured by other MEDA sensors and additional instruments in Perseverance. From the two altitudes sampled with ATS, and additional data from the MEDA Thermal InfraRed Sensors (TIRS), which measure ground temperature and air temperature at 40m, we can obtain the near-surface vertical temperature profile for specific sols in which thermal contamination is moderate in all sensors. This allows us to study the evolution of the diurnal convective cycle and the vertical temperature gradient. In addition, the Supercam microphone can also deduce the average air temperature from the ground up to 2.1m high thanks to sound speed measurements during Supercam’s laser zapping rocks. Therefore, it gives an additional hint into the thermal gradient. Furthermore, the amplitude of the thermal oscillations characterizes the thermal turbulence and we present the spectra of turbulence for convective and non convective hours on different moments of the mission. Finally, we will show how the measured thermal data compares with model predictions of the daily cycle of temperatures, expected magnitude of thermal oscillations, and the seasonal evolution.

How to cite: Munguira, A., Hueso, R., Sánchez-Lavega, A., de la Torre-Juarez, M., Chavez, Á., Martínez, G., Newman, C., Banfield, D., Vicente-Retortillo, Á., Lepinette, A., Pla-García, J., Rodríguez-Manfredi, J. A., Chide, B., Bertrand, T., Sebastián, E., Gómez-Elvira, J., Lemmon, M., Tamppari, L., Lorenz, R., and Viudez-Moreiras, D. and the additional MEDA team members: Mars 2020 MEDA ATS Measurements of Near Surface Atmospheric Temperatures at Jezero, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7047, https://doi.org/10.5194/egusphere-egu22-7047, 2022.

Unravelling the tectonic styles that affected the Martian crust is crucial to better understand the evolutionary stages that a rocky planet can experience. Here, we explore the tectonic setting of a key region of Mars, namely the Claritas Fossae (CF). The CF is located in the Highlands to the south-west of the Valles Marineris and is characterized by an elongated system of scarps and troughs, fault sets, and grabens, nearly N-S trending. These morphotectonic features strongly resemble terrestrial grabens (e.g.; Thingvellir in south Iceland) and, for this reason, the CF has been interpreted as a rift-like system (Hauber & Kronberg, 2005).

In this work we apply a kinematic numerical forward modelling (HCA method; Salvini & Storti, 2004) to reproduce the geometry of the main fault(s) that likely generated the CF in order to better understand the leading tectonic mechanisms. This method allows replicating the superficial morphologies by considering the development of one or multiple faults with given geometry, throw and displacement rate and the relative movement between hanging-wall and foot-wall crustal blocks. It has been successfully used to simulate tectonically controlled morphologies on Earth such as ice buried landscape in the interiors of Antarctica (Cianfarra & Salvini, 2016), a negligible erosional environment considered as a good Martian analogue. In our model, we reproduced the morphology of the central-northern sector of the CF, characterized by an asymmetric valley with a steeper eastern slope and a gently rounded western one, along a topographical profile perpendicular to the strike of the main structure. The eastern valley slope allows locating the upper tip of the fault for the modelling in which we set the crustal thickness (i.e., the bottom of the model) to 70 km (Watters et al., 2007), considered no significant rheological vertical variation and tried different values of initial dip in the range 50°-70° and throw in the range  1000-2000 m. The preliminary results of our modelling show that the topography, including the rounded shape of the western slope, is well replicated by a crustal (listric) normal fault characterized by an initial dip of ca. 60° that gently decrease to ca. 40° and a throw of ca. 1800 m. This allows including the development of the CF in a past extensional tectonic regime of regional relevance. Further modelling on new topographical profiles to the north and to the south respect to the already modelled one will allow better highlighting the 3D shape of the main CF fault and the presence of further secondary but not negligible faults.

Hauber, E., & Kronberg, P. (2005). The large Thaumasia graben on Mars: Is it a rift?. J. Geoph. Research: Planets

Salvini, F., & Storti, F. (2004). Active-hinge-folding-related Deformation and its Role in Hydrocarbon Exploration and DevelopmentInsights from HCA Modeling.

Cianfarra, P., & Salvini, F. (2016). Origin of the adventure subglacial trench linked to Cenozoic extension in the East Antarctic Craton. Tectonophysics

Watters, T. R., McGovern, P. J., & Irwin Iii , R. P. (2007). Hemispheres apart: The crustal dichotomy on Mars. Annu . Rev. Earth Planet. Sci.

How to cite: Balbi, E., Cianfarra, P., Ferretti, G., Crispini, L., and Tosi, S.: Modelling the extensional tectonic setting of the Claritas Fossae, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7683, https://doi.org/10.5194/egusphere-egu22-7683, 2022.

MEDA HS is the relative humidity sensor on the Mars 2020 Perseverance rover provided by the Finnish Meteorological Institute (FMI). The sensor is a part of Mars Environmental Dynamic Analyzer (MEDA), a suite of environmental sensors provided by Centro de Astrobiología in Madrid, Spain.

The accuracy requirement for MEDA HS relative humidity was ±10% RH for temperatures above -70 ºC, and ±20% RH for temperatures between -83...-73 ºC. Dynamic range from 0 to 100% RH shall cover the whole Martian temperature range from -83 ºC to -3 ºC. However it must be noted that during the daytime when the relative humidity drops close to zero, the readings are not scientifically meaningful due to the large relative uncertainty.

MEDA HS flight model was tested and calibrated in Mars-like dry environment at FMI together with flight spare and ground reference models from +22 ºC to -70 ºC and in saturation conditions from -40 ºC down to -70 ºC. Further, the MEDA HS flight model final calibration is complemented by calibration data transferred from an identical ground reference model which has gone through extensive humidity calibration test campaign at DLR PASLAB. The MEDA HS has been calibrated to full relative humidity range between -70 to -40 ºC in CO₂ in the pressure ranges from 5.5 to 9.5 hPa, representative of Martian surface atmospheric pressure, and partial range up to +22 ºC. For lower temperatures the results are extrapolated.

The complex analysis of the MEDA HS measurement uncertainty has now been finalized and the results are presented in the conference. It has been found that the sensor exceeds the design requirements and will provide high accuracy relative humidity measurements from the Martian surface to provide important meteorological observations and to support MEDA and other M2020 investigations.

How to cite: Hieta, M., Polkko, J., Jaakonaho, I., Genzer, M., Tabandeh, S., Rodríguez Manfredi, J. A., Tamppari, L., and de la Torre Juarez, M.: Accuracy of the relative humidity sensor MEDA HS onboard Perseverance rover, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7888, https://doi.org/10.5194/egusphere-egu22-7888, 2022.

Mars climate modelling is essential for understanding the atmosphere of a planet with limited in-situ observations. Such research is crucial if humanity will ever hope to explore the red planet in the coming decades. There are already Global Climate Models (hereafter; GCMs) for Mars that are tackling this challenge, but there are still processes that are poorly understood or difficult to simulate, such as inter-annual dust storms or a dynamically-calculated CO₂ ice cycle which affects global pressure changes. In order to address these issues in current Mars modelling, we propose a GCM capable of reproducing similar results by using different parameterisation. This multi-faceted approach would be pivotal in tackling the aforementioned issues, in addition to providing validation of modelling techniques in extreme conditions. 

We adapt a highly-sophisticated and modular GCM, the Met Office Unified Model, currently routinely employed for weather and climate prediction on Earth, to the present climate of Mars. We detail the key climate processes driving Mars' atmosphere and how we characterise them, namely:

• Dust
• Orography
• Orbital parameters
• Atmospheric composition and pressure
• Atmospheric H₂O
• CO₂ ice

By incrementally adapting schemes already established and used extensively for Earth simulations, we can reproduce a comprehensive and complex climate model of Mars, whilst simultaneously assessing the significance of each process. To verify our model, we compare our GCM against in-situ data from the Viking landers and outputs from the LMD Mars GCM. Through this, we demonstrate how we are able to reproduce key processes in the Martian atmosphere across its seasons, between which conditions can vary greatly. We then speculate what processes still need implementation or refinement and the impact they may have on our current outputs. 

We will finish by detailing the remaining schemes to be implemented and how they might impact the output of our GCM, namely; a CO₂ ice scheme and atmospheric moisture. The implementation of these processes will further increase the validity and accuracy of our results. Potential future work would include investigating diurnal fluctuations or inter-annual phenomena. Our GCM and modelling methods would eventually aim to expand the capabilities of the wider Mars-modelling community, the benefits of which, will bring us closer to unlocking and understanding the intricacies of Mars' unique environment.

How to cite: McCulloch, D., Mayne, N., Bate, M., and Sergeev, D.: Adapting an Earth Global Climate Model for a Modern-day Martian climate., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7939, https://doi.org/10.5194/egusphere-egu22-7939, 2022.

In the past decades, numerous hydrated silicates have been detected at the surface of Mars from orbital and in situ characterization. The study of their distribution and their quantification can enable to trace the history of water at the surface of the red planet. By quantifying the content of each minerals at the hydrated sites, we can have an estimation of the water content stored at the surface within these minerals. Our study is based on the modal compositional maps of 11 hydrated silicates that were detected with the OMEGA/MEx instrument (Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité). The maps were computed using a radiative transfer model applied to the hyperspectral images of OMEGA, where hydrated minerals features were previously detected. They results in global maps of modal composition at a resolution sub-kilometric of: Fe,Mg,Al-phyllosilicates, Al-smectite, AlSiOH, Opal, Mg-carbonates, Chlorite, Fe/Mg-Micas, Serpentine and Fe-hydroxide and were recently published in Riu et al., 2022. By estimating the water content of each individual end-members we were able to convert the 11 mineralogical maps into one final map of H₂O content (in wt%). The average content of water, based on the content stored in hydrated silicates, is estimated to be slightly above 5 wt%, with some rare occurrences > 20 wt%. The ongoing studies now aim at a detailed analysis of the water distribution in order to look for new regions with high past aquability (stable liquid water) potential and/or exobiological potential, if such locations exist. The map will be studied locally in combination with high resolution images in order to correlate the high-water content with their context and highlight new regions of interest. A detailed analysis of the ExoMars22 Rosalind Franklin Rover is also foreseen in order to help the future in situ analysis of the ExoMars mission and contribute to ISRU (in situ ressource utilization).

How to cite: Riu, L., Carter, J., and Poulet, F.: Estimation of H2O content (in wt%) stored in hydrated silicates at Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9874, https://doi.org/10.5194/egusphere-egu22-9874, 2022.

The Emirates Mars Ultraviolet Spectrometer (EMUS) instrument is one of three science instruments on board the “Hope Probe” of the Emirates Mars Mission (EMM). EMM arrived at Mars on February 9 2021, in order to explore the global dynamics of the Martian atmosphere, while sampling on both diurnal and seasonal timescales. The EMUS instrument is a far-ultraviolet imaging spectrograph, jointly developed by the Mohammed Bin Rashid Space Centre (MBRSC) in Dubai, UAE and the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder, which measures emissions in the spectral range 100-170 nm. Using a combination of its one-dimensional imaging and spacecraft motion, it makes two-dimensional far-ultraviolet images of the Martian disk and near-space environment including the Lyman beta and alpha atomic hydrogen emissions (102.6 nm and 121.6 nm), two atomic oxygen emissions (130.4 nm and 135.6 nm), and the carbon monoxide fourth positive group band emission (140-170 nm). Measurements of radiance at these wavelengths are used to derive the column abundance of atomic oxygen and carbon monoxide in the Martian thermosphere, and the density of atomic oxygen and atomic hydrogen in the Martian exosphere both with spatial and sub-seasonal variability. We will present a survey of results from EMM/EMUS including observed variability in atomic oxygen and carbon monoxide emission, two kinds of aurora, and the status of atmospheric retrievals.

How to cite: Chaffin, M., Almazmi, H., Chirakkil, K., Correira, J., Deighan, J., England, S., Evans, J. S., Fillingim, M., Holsclaw, G., Jain, S., Lillis, R., Lootah, F., Raghuram, S., and Al Matroushi, H.: Key Results from the Emirates Ultraviolet Spectrometer on the Emirates Mars Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10731, https://doi.org/10.5194/egusphere-egu22-10731, 2022.

Many cones on Isidis Planitia form subparallel chains several kilometers in length. This region have characteristic pattern of cones or cone chains- called a “fingerprint” [1]. Our analysis of chains of cones indicates that they can be grouped in larger systems. We considered one of these systems in the northwestern part of Isidis (central location: 14.235°N; 83.096°E).

We selected one standout spectrum that comes from the CRISM FRT00009260 scene but is typical for the entire image area. The scene just comes from the northwestern part of Isidis, where the characteristic chains of cones are visible. The types of cones from our division [2], belong to the group of chains of separate cones and without a furrow. The spectrum shows the minima 1.49; 1.98; 2.04 µm which we assigned to individual minerals. Additionally, the ~ 2 µm range is disturbed by Martian CO₂ influences, which is caused by the imperfect separation of the atmosphere by the “volcano - scan algorithm” (by the atmosphere above Olympus Mons). Gypsum appears to be the most suitable mineral for these minima, although alunites can also be considered. The clay minerals widespread on Mars do not resemble in the observed minima. From the generated endmembers, it can be seen that minerals are accumulated around the cones.

Gypsum is a mineral formed in the process of evaporation and crystallizes from salty, drying water reservoirs. Because Isidis might once have been a highly saline reservoir, gypsum crystallization could occur under such conditions, especially in depressions. Alunites, on the other hand, are products of volcanic exhalation, which would explain the origin of the cones. Common alunites have been found on the La Fossa Crater Volcano, Aeolian Islands [3] as volcanic exhalations and in the vicinity of Las Vegas, Nevada, where alunites with gypsum were mapped based on aerial photos [4]. On Mars in the northeast of Hellas Basin, gypsum and ammonioalunites were interpreted on the basis of the PFS and OMEGA (MEX) spectra [5], [6]

These are our preliminary comparisons that still require further evaluation. The next stage of the work will be to explain the mechanism of the formation of these forms, based on known geological phenomena but in relation to Mars. We want to clarify whether the designated areas were created in the same geological processes, or whether a different mechanism is responsible for the differences in these forms. We take the phenomenon into account that instability of water in the upper layers of the regolith could cause rapid degassing of the regolith [7].

References: [1] Guidat, T. et al. (2015) Earth and Planet. Sci. Let . 411, 253-267. [2] Zalewska N. et al. (2021) LPS 52nd, Abstract # 2710. [3] Parafiniuk J. (2012) Bulletin of the Polish Geolog. Instit. 452, 225-236. [4] Kirkland E. et al. (2007) LPS XXXVIII, Abstract # 2232. [5] Zalewska N. (2013) Planet. Space Sci. 78, 25-32. [6] Zalewska N. (2014) GeoPl. Earth and Planet. Sci. 65-76. [7] Czechowski L. et al. (2021) LPS 52nd, Abstract # 2740.

How to cite: Zalewska, N., Czechowski, L., and Ciążela, J.: Mineralogy of cones in the western part of Isidis Planitia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10765, https://doi.org/10.5194/egusphere-egu22-10765, 2022.

The Micro Context Camera (MCC) of PIXL onboard Perseverance has successfully completed commissioning. It meets all requirements and has led to the first proximity science using the PIXL instrument. This abstract presents the inflight system performance.

The pre-launch calibration of the MCC system has been verified on the surface of Mars. Distance measurements to Martian Rock surfaces are performed at with an accuracy better than 100 µm. This is accomplished utilizing Structured Light over the full diurnal thermal environment on the surface of Mars. The PIXL sensor unit is mounted on the turret of the Mars Perseverance rover arm. This autonomous navigation capability has enabled safe approaches of rugged surfaces, without ground intervention or interaction with e.g. a touch plate. It has also enabled proximity science of the Martian surface at unprecedented accuracy. The autonomy further enables PIXL to capture high resolution XRF scans while continuously maintaining optimal distance and focus of the X-ray beam. The system’s performance is robust enough for PIXL to navigate relative to both abraded and natural surfaces.

The MCC also has the capability of multispectral imaging. This has provided information for the interpretation of surface lithology and it also provides additional information for the XRF measurements interpretation due to its high resolution.

The MCC’s Terrain Relative Navigation (TRN) autonomous functionality has also been demonstrated in the Martian environment. This capability is essential for PIXL to maintain the planned scan trajectory relative to the rock surface – as PIXL’s longer duration scans (up to 10 hours) is relying on stability and capability to compensate for the diurnal thermal environment causing position drift relative to the Martian rock surface. We present the measured performance on Mars. This show that the system performs reliably on both high and low topography rock surfaces with and without dust coverage. This has enabled PIXL to autonomously track and self-correct for any drift away from the planned scan trajectory.

How to cite: Pedersen, D., Henneke, J., Jørgensen, J. L., Benn, M., Denver, T., Timmermann, L., Liebe, C. C., Denise, R., Elam, T., Wade, L., Foote, M., Hurowitz, J., and Allwood, A.: PIXL’s Micro Context Camera performance on the surface of Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11234, https://doi.org/10.5194/egusphere-egu22-11234, 2022.

In 2022, ESA/ROSCOSMOS will launch ExoMars2022 rover mission to Mars. The selected landing site for the mission is Oxia Planum, a Noachian, phyllosilicate-bearing plain located between Mawrth Vallis and Ares Vallis. The Fe,Mg-rich clay mineral detected at Oxia Planum are one of the largest exposures of this type on Mars. They clearly record past water-rock interactions and as such are promising target to answer scientific questions that are the objectives of the ExoMars 2022 mission in terms of past water-rich environment and both ancient and present habitability of the planet.

NIR spectral features of the phyllosilicates at Oxia suggest some kind of Fe-rich vermiculite and/or saponite. Survey of Fe-rich terrestrial vermiculite-bearing rocks and characterization by powder near-infrared and X ray diffraction analyses (Krzesinska et al, 2021) showed that the best spectral analogy is shown by the basaltic tuffs from Granby, Massachusetts, USA. The tuffs have been altered and Fe-rich clays resides in amygdales of supposedly hydrothermal origin (April and Keller, 1991).

The analogue was incorporated to the Planetary Terrestrial Analogue Library (PTAL) collection (Dypvik et al., 2021, www.ptal.eu). As a part of collection, it is further characterized for purposes of supporting the ExoMars mission science.

As shown by bulk analysis of powdered samples, Granby tuffs represent fine-scale mixture of phyllosilicates (Krzesinska et al., 2021). Based on bands between 2.3 and 2.5µm in NIR, vermiculite and saponite are intergrowing with various proportions. For Oxia Planum, better spectral match is shown by samples dominated by vermiculite rather than mixed with saponite.

Here we report an in-situ, micron-scale combined analysis on the same sample by the instrument of MicrOmega (NIR), RLS (RAMAN) completed by sub-micron EDX analysis. Such analysis allows a more detailed characterization of phyllosilicate constituents and understanding their spectral manifestation. This is important to prepare the future in situ scientific investigations on Mars and will also bring a better understanding of the Granby clays that could represent a unique bridge of solid solution between chlorite and saponite (April and Keller, 1991).

How to cite: Bultel, B., Krzesinska, A., Veneranda, M., Loizeau, D., Pilorget, C., Hamm, V., Lourit, L., Lequertier, G., Bibring, J.-P., and Werner, S. C.: Micro-scale characterization of vermiculite-rich sample from Granby Tuff, an analogue to Oxia Planum clays, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11272, https://doi.org/10.5194/egusphere-egu22-11272, 2022.

The Planetary Instrument of X-ray Lithochemistry (PIXL), onboard the Mars 2020 rover Perseverance, is designed to measure the chemical composition of Martian materials with a spatial resolution of around 100 µm. The surface of Mars is notoriously dusty and even thin layers of dust within the measurement frame will impact the instrument signal, potentially leading to misinterpretation of an underlying chemical composition if not appropriately accounted for. Therefore, knowledge about the dust composition, concentration and distribution is important, both when deciding where to perform measurements and in data analyses.

Herein we present methods for generating high precision dust profiles of Martian surfaces by utilizing the Optical Fiducial System (OFS) component of the PIXL instrument. The OFS consist of a Micro Context Camera (MCC) and a FloodLight Illuminator (FLI). The MCC captures images with a resolution better than 50 µm/pixel at the instrument’s nominal distance of 25 mm, directly enabling the optical characterization of dust, and other components, on these surfaces. The FLI is equipped with a total of 24 light emitting diodes (LEDs), in four groups centered at UV (385 nm), Blue (450 nm), Green (530 nm), and NIR (735 nm), enabling multispectral capabilities. This multispectral floodlight capability directly facilitates dust detection by the MCC, and utilizing the precision of the MCC, the spatial distribution of dust is better constrained.

We present dust profile maps acquired by the PIXL OFS on Martian surfaces and present similar results derived from the rover-mounted calibration targets. In demonstrating the quality of the maps produced, we can improve future scientific analyses while furthermore improving the operational efficiency and data quality of the Perseverance mission through the potential future implementation of a closed-loop autonomous dust-avoidance routine, utilizing the macro capabilities of the PIXL OFS.

The author recognises the great contribution made by the PIXL Team and the broader Mars 2020 Team.

How to cite: Henneke, J., Pedersen, D. A. K., Jørgensen, J. L., Liu, Y., Allwood, A. C., Hurowitz, J., Schmidt, M. E., and VanBommel, S. J.: Profiling Martian Dust Using PIXL Images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11769, https://doi.org/10.5194/egusphere-egu22-11769, 2022.

We will investigate the impact of day-night temperature and compositional gradients at the Martian terminator on the retrieval of vertical profiles of ozone obtained from NOMAD-UVIS solar occultations. 

Rapid variations in species concentration at the terminator have the potential to cause asymmetries in the species distributions along the line of sight of a solar occultation experiment. Ozone, in particular, displays steep gradients across the terminator of Mars due to photolysis [1]. Nowadays, most of the retrieval algorithms for solar and stellar occultations rely on the assumption of a spherically symmetrical atmosphere. However, photo-chemically induced variations near sunrise/sunset conditions need to be taken into account in the retrieval process in order to prevent inaccuracies.

NOMAD (Nadir and Occultation for MArs Discovery) is a spectrometer composed of 3 channels: 1) a solar occultation channel (SO) operating in the infrared (2.3-4.3 μm); 2) a second infrared channel LNO (2.3-3.8 μm) capable of doing nadir, as well as solar occultation and limb; and 3) an ultraviolet/visible channel UVIS (200-650 nm) that can work in the three observation modes [2,3]. 

The UVIS channel has a spectral resolution <1.5 nm. In the solar occultation mode, it is mainly devoted to study the climatology of ozone and aerosols [4,5,6].

Since the beginning of operations, on 21 April 2018, NOMAD-UVIS acquired more than 8000 solar occultations with an almost complete coverage of the planet.

NOMAD-UVIS spectra are simulated using the line-by-line radiative transfer code ASIMUT-ALVL developed at IASB-BIRA [7]. In a preliminary study based on SPICAM-UV solar occultations (see [8]), ASIMUT was modified to take into account the atmospheric composition and structure at the day-night terminator. As input for ASIMUT, we used gradients predicted by the 3D GEM-Mars v4 Global Circulation Model (GCM) [9,10]. 

References
[1] Lefèvre, F., Bertaux, J.L., Clancy, R. T., Encrenaz, T., Fast, K., Forget, F., Lebonnois, S., Montmessin, F., Perrier, S., Aug. 2008. Heterogeneous chemistry in the atmosphere of Mars. Nature 454, 971–975.
[2] Vandaele, A.C., et al., Planetary and Space Science, Vol. 119, pp. 233–249, 2015. 
[3] Neefs, E., et al., Applied Optics, Vol. 54 (28), pp. 8494-8520, 2015.
[4] M.R. Patel et al., In: Appl. Opt. 56.10 (2017), pp. 2771–2782. DOI: 10.1364/AO.56.002771. 
[5] M.R. Patel et al., In: JGR (Planets), Vol. 126, Is. 11, 2021.
[6] Khayat, Alain S. J., et al., In: JGR (Planets), Vol. 126, Is. 11, 2021.
[7] Vandaele, A.C., et al., JGR, 2008. 113 doi:10.1029/2008JE003140.
[8] Piccialli, A., Icarus, submitted.
[9] Neary, L., and F. Daerden (2018), Icarus, 300, 458–476, doi:10.1016/j.icarus.2017.09.028.
[10] Daerden et al., 2019, Icarus 326, https://doi.org/10.1016/j.icarus.2019.02.030

How to cite: Piccialli, A., Vandaele, A. C., Neary, L., Willame, Y., Aoki, S., Trompet, L., Depiesse, C., Viscardy, S., Daerden, F., Erwin, J., Thomas, I. R., Ristic, B., Mason, J. P., Patel, M., Khayat, A., Wolff, M., Bellucci, G., and Lopez-Moreno, J. J.: Impact of gradients at the Martian terminator on the retrieval of ozone from TGO/NOMAD-UVIS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12125, https://doi.org/10.5194/egusphere-egu22-12125, 2022.

Planetary Terrestrial Analogue Library (PTAL) is a newly built collection of rocks and spectral data aiming to support interpretation of data from Mars and small bodies of the Solar System [1]. It contains spectral data by NIR, Raman and LIBS, validated by XRD and microscopic characterization [2,3,4]. Since September 2021, the PTAL library is public and freely accessible (www.ptal.eu), and the physical collection of witness rocks is available for further studies. PTAL is collection of natural rocks and not individual minerals what gives better insight into mineralogy and geochemistry as e.g. overlapping vibrational absorption features of minerals are included. Although the spectral analogy never implies exact parallelism in processes of deposit formation, reliable identification of specific minerals can shed light on recorded evolution and alterations. Here we present the overview of analogues and assess their fidelity in terms of information about composition (mineralogy and geochemistry) of Martian crust and alteration environments.

PTAL consists of 106 rock samples from 19 diverse localities on Earth [1]. The collection contains a variety of volcanic rocks, from picrobasalts to phonolites. Sampling sites include tholeiitic basalts from Iceland, ferropicrites from Rum (Scotland), alkali-rich rocks of metasomatized origin from Canary Islands and Tenerife, basaltic tuffs and ash-fall deposits from the Granby formation (USA) with clay-infilled amygdales, as well as serpentinised peridotites from the Leka ophiolite complex (Norway). Collected rocks are good analogues for processes of martian mantle-plume fed volcanism as well as for evolution of alkali-rich crustal units on Noachian Mars. Additionally they record processes of metasomatism, deuteric and hydrothermal alteration. They are never perfect geochemical analogues to Martian crust, which is a consequence of inherited differences between the two planets, e.g. Fe and Mn content or volatile abundances. PTAL initial studies show, however, that studies of alteration pathways as a function of protolith composition are possible with these rocks, despite geochemistry mismatches [5].

PTAL contains also samples from diverse surface alteration environments and from range of climatic environments, including hot and cold deserts: John Day Formation in Oregon (USA), Dry Valleys in Antarctica, Otago Formation (New Zealand), Jaroso Ravine and Rio Tinto (Spain). These analogues contain minerals such as jarosite, hematite, or Fe-rich vermiculite and therefore good geochemical and mineralogical analogies to Mars targeted sites can be obtained. However, care is needed when processes of formation inferred [e.g. 5], as peculiar conditions leading to formation of minerals can be obtained in a spectrum of environments. PTAL strength is that it samples a sequence of alteration products, allowing detailed mineralogical and geochemical comparative analyses within alteration environment to shed light on the potential parallelism of formation process [5].

Acknowledgement: PTAL was funded by the EU Horizon 2020 Research and Innovation Programme (Grant Agreement 687302).

[1] Dypvik et al., 2021. Planetary and Space Science 208, 105339

[2] Lantz et al., 2020. Planetary and Space Science 189: 104989

[3] Loizeau et al., 2022. Astrobiology, accepted.

[4] Veneranda et al., 2020. Journal of Raman Spectroscopy 51: 1731-1749

[5] Krzesinska et al. 2021. Astrobiology 21: 997-1016

How to cite: Krzesinska, A. M., Bultel, B., and Werner, S. C.: Analogues for Martian crustal and aqueous processes: Lessons learnt from mineralogy and geochemistry of rocks in the PTAL collection., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12286, https://doi.org/10.5194/egusphere-egu22-12286, 2022.

We report here the results of more than 2 years of monitoring the rotation of Mars with the RISE instrument on InSight. Small periodic variations of the spin axis orientation, called nutations, can be extracted from the Doppler data with enough precision to identify the influence of the Martian fluid core.  For the first time for a planetary body other than the Earth, we can measure the period of the Free Core Nutation (FCN), which is a rotational normal mode arising from the misalignment of the rotation axes of the core and mantle. In this way, we confirm the liquid state of the core and estimate its moment of inertia as well as its likely size.

The FCN period depends on the dynamical flattening of the core and on its ability to deform. Since the shape and gravity field of Mars deviate significantly from those of a uniformly rotating fluid body, deviations from that state can also be expected for the core. Models accounting for the dynamical shape of Mars can thus be tested by comparing core shape predictions to nutation constraints. The observed FCN period can be accounted for by interior models having a very thick lithosphere loaded by degree-two mass anomalies at the bottom.

The combination of nutation data and interior structure modeling allows us to deduce the radius of the core and to constrain its density, and thus, to address the nature and abundance of light elements alloyed to iron. The inferred core radius agrees with previous estimates based on geodesy and seismic data. The large fraction of light elements required to match the core density implies that its liquidus is significantly lower than the expected core temperature, making the presence of an inner core highly unlikely. Besides, the existence of an inner core would lead to an additional rotational normal mode the signature of which has not been detected in the RISE data.

How to cite: Le Maistre, S., Rivoldini, A., Caldiero, A., Yseboodt, M., Baland, R.-M., Beuthe, M., Van Hoolst, T., Dehant, V., Folkner, W., Buccino, D., Kahan, D., Marty, J.-C., Antonangeli, D., Badro, J., Drilleau, M., Konopliv, A., Peters, M.-J., Plesa, A.-C., Samuel, H., and Tosi, N. and the InSight/RISE team: The deep interior of Mars from nutation measured by InSight RISE, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12428, https://doi.org/10.5194/egusphere-egu22-12428, 2022.

Across the surface of Mars there is evidence of past lacustrine and evaporitic environments found within basins and craters, where often layered sedimentary deposits and hydrated minerals are observed. However, the intensity, duration and precise phases of water cycle activity during their deposition remain unresolved. Although several geological processes and locations on Earth have been previously proposed as examples to describe these deposits on Mars, we lack a strong visualization of what water activity might have looked like during evaporitic stages within basins and craters. The Makgadikgadi Salt Pans of Botswana, where once the Makgadikgadi Lake existed, is a present evaporitic environment rich in hydrated minerals and water activity. It is a depression located at the southwestern end of a northeast-southwest set of graben. Faults have been previously proposed to have been pathways for groundwater to enter basins and craters on Mars, which then contributed to both the deposition and alteration of the sedimentary deposits. Thus, imaging the subsurface of a similar environment on Earth can help us to better understand how water processes on Mars might have continued as the Martian global climate became drier.

Through remote sensing techniques, we located areas within the pans where several regional faults occurred then conducted four electrical resistivity surveys perpendicular to the faults using an IRIS Syscal Pro imaging resistivity meter. Fault locations were determined by using a combination of topographic and aeromagnetic data. Fault scarps were observed terminating at the shorelines of the pans and their azimuths were used to trace the best locations of the faults underneath the sediment within the pans. These locations were then constrained further by using the aeromagnetic data which showed regional dikes that had been laterally offset in areas associated with the fault scarps, as well as anomalies that ran parallel and adjacent to the fault scarps. We successfully laid one 840 m and three 1,200 m long survey lines. The four survey lines intersected where these faults were determined to occur and were able to image the subsurface up to a depth of approx. 92 m.

In this way, we can detect low electrical resistance in void space produced by any faults and associated fractures in the overlaying water saturated sediment. Specific craters noted for their similarity to the study area include several in Arabia Terra (e.g. Oyama, Kotido, Firsoff and Jiji), and also Gale crater. The analog concept could also potentially be connected to layered deposits in Meridiani Planum and Valles Marineris. This work has wide implications for determining how putative water table elevations could have interacted within sediment filled craters on Mars by resolving areas of low resistivity and identifying faults that water could have used as pathways, which is not possible with the current instrumentation present on Mars. Results can also allow us to better infer what the underlying lithology of layered deposits within craters might look like. Furthermore, it demonstrates the scientific importance of future missions to employ subsurface imaging techniques on Mars.

How to cite: Schmidt, G., Luzzi, E., Franchi, F., Selepang, A. T., Hlabano, K., and Salvini, F.: Constraining the Movement of Groundwater Within Playa Environments on Mars Through Subsurface Imaging of the Makgadikgadi Salt Pans of Botswana, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12535, https://doi.org/10.5194/egusphere-egu22-12535, 2022.

The ExoMars Programme will send a rover to Mars in 2022 equipped with a 2 m drill which will search for evidence of extinct life below the surface. This project is focused on the stereo vision systems of the rover, and how better 3-D information can be extracted from the camera images. This is explored through both experimental and simulation-based approaches. The experimental approach was to build a hardware emulator of the three stereo pairs: the Wide-Angle Cameras (WACs) from the Panoramic Camera instrument (PanCam), and the Navigation Camera (NavCam) and Localisation Camera (LocCam) systems. Point clouds were generated from the emulator data and compared against a (LIDAR) generated point cloud to determine which combination of cameras yields the best point clouds. The comparison methods were as follows: the number of tie points, the number of dense cloud points, coordinate extent, surface density, nearest neighbour distance (NND) to the LIDAR cloud, and measurement of a known target. One set of experiments compared the four mast head stereo cameras (WACs and NavCams) and the second set compared all six stereo cameras (WACs, NavCams, and LocCams). The six-view point cloud was the closest match to the LIDAR in terms of mean NND to the LIDAR point cloud, but it was only marginally better than the five-view point clouds and the four-view point cloud made of the WACs and NavCams. The conclusions from both sets of experiments are that the three stereo camera pairs do not contribute equally to improvements in the point clouds generated through photogrammetry. The emulator WACs are the most suited to photogrammetric reconstruction, followed by the emulator NavCams and finally the emulator LocCams.

How to cite: Bohacek, E.: The 3-D capability of science and engineering cameras on the ExoMars rover, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12935, https://doi.org/10.5194/egusphere-egu22-12935, 2022.

Since the 90s, an ever-increasing number of missions to Mars have been conducted which offer a plethora of information about the red planet. This information also led to the rapid development and advancement of prominent scientific fields in space and planetary exploration, such as astrobiology and ISRU technologies. The experimentation and research requirements of those fields, as well as, the need for better vehicle and instrument testing for further development, so that they will better operate on Martian conditions and its surface, increase in significance. Currently, this is performed with the use of natural (Analogue) and synthetic (Simulant) Geomaterials. 

However, the accessibility and the analysis of analogue and simulant data requires a thorough literature review in order to  identify implications for future research. In our latest research work, we conducted this detailed review and we identified, grouped, and analysed a number of implications that pertain mostly to the synthesis procedures of simulants, but also extend to the in situ analytical data from Mars that are used as a reference. Furthermore, we identified an urgent need for improving the current state of simulant research, as it is currently very time consuming and has implications, in hope that systematic work on the topic will culminate in a general standardisation effort.

The current work was done by analysing data on all available simulant geomaterials in order to provide recommendations and suggestions for mitigation actions for their development and their use during research, as well as to advocate the needs for a unified standardisation system. These actions include: (a) the consolidation of existing literature into database formats with easy access, based on (b) the development of a new informational construct based on ontologies and semantics, (c) to propose a classification system for simulants that is missing from the literature, and (d) assist the simulant geomaterial selection process through a proposed step algorithm. The ontological and semantic mindset should be followed at every step, and it is incorporated into the classification system, thus enabling easy access and interpretation by both humans and machines. This set of tools and recommendations should be applicable on all simulant related facets of space exploration.

How to cite: Stavrakakis, H.-A., Argyrou, D., and Chatzitheodoridis, E.: A new classification and terminology system towards the development and utilisation of Martian simulants, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12988, https://doi.org/10.5194/egusphere-egu22-12988, 2022.

The northern hemispheric electron density (N_e) data acquired by the Radio Occultation Science Experiments (ROSE) onboard the Mars Atmosphere and Volatile Evolution (MAVEN) have indicated more complicated ionospheric structure of Mars than previously thought.  Large variations in the topside N_e scale heights are observed presumably in response to the outward flow of the ionospheric plasma or changes in plasma temperatures.   We use our 1-D chemical diffusive model coupled with the Mars - Global Ionosphere Thermosphere Model (M-GITM) to interpret the northern upper ionospheric structure at Mars.  The primary source of ionization in the model is due to solar EUV radiation. Our model is a coupled finite difference primitive equation model which solves for plasma densities and vertical ion fluxes.  The photochemical equilibrium for each ion is assumed at the lower boundary of the model, while the flux boundary condition is assumed at the upper boundary to simulate plasma loss from the Martian ionosphere.  The crustal magnetic field at the measured N_e locations is weak and mainly horizontal and does not allow plasma to move vertically.   Thus, the primary plasma loss from the topside ionosphere at these locations is most likely caused by diverging horizontal fluxes of ions, indicating that the plasma flow in the upper ionosphere of Mars is controlled by the solar wind dynamic pressure.  We find that the variation in the topside N_e scale heights is sensitive to magnitudes of upward ion fluxes derived from ion velocities that we impose at the upper boundary to explain the topside ionospheric structure.  The model requires upward velocities ranging from 50 ms^-1 to 90 ms^-1 for all ions to ensure an agreement with the measured N_e profiles. The corresponding outward fluxes in the range 1.1 x 10⁶ – 5.8 x 10⁶ cm^-2 s^-1 are calculated for O₂⁺ compared to those for O⁺ in the range 3.8 x 10⁵ – 6.7 x 10⁵ cm^-2 s^-1.  The model results for the northern N_e profiles will be presented in comparison with the measured N_e profiles.  

How to cite: Majeed, T., AlSuwaidi, H., Bougher, S. W., and Morschhauser, A.: A Model Analysis of the Northern Ionospheric Structure Observed with the MAVEN/ROSE at Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13045, https://doi.org/10.5194/egusphere-egu22-13045, 2022.

Observations of excited hydroxyl (OH^*) emissions are broadly used for inferring information about atmospheric dynamics and composition. It plays an important role in the photochemical balance and is affected by transport and mixing processes. We present several analytical approximations for characterizing the hydroxyl layer in the Martian atmosphere. They include OH^* number density at the maximum and the height of the peak, along with the relations for assessing different impacts on the OH^* layer at nighttime conditions. These characteristics are determined by the ambient temperature, atomic oxygen concentration and their vertical gradients. The derived relations can be used for analysis of airglow measurements and interpretation of its variations.

How to cite: Shaposhnikov, D., Grygalashvyly, M., Medvedev, A. S., Sonnemann, G. R., and Hartogh, P.: Simplified Relations for the Martian Nighttime Hydroxyl Layer Suitable for Interpretation of Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13086, https://doi.org/10.5194/egusphere-egu22-13086, 2022.

Orbital data from the Colour and Stereo Surface Imaging System (CaSSIS) onboard the ExoMars Trace Gas Orbiter showed interesting images of the circumpolar areas during spring. The winter-formed dusty CO2 ice cap goes under self-cleaning processes producing a translucent slab. With grazing spring sunlight, it starts to sublimate at the base and from overpressure, cold jets erupt leaving erosion marks in the underlying substrate and dust/sand deposits at the surface. This model, proposed by Kieffer, is commonly accepted to explain dark spots and fans deposits as well as spiders.

To test different aspects of this model, we combine observational data from CaSSIS with experimental work for which Martian temperature and pressure at high latitudes could be reached in a simulation chamber. Preliminary results on sinking analogous dust material (MGS-1) on a CO2 ice slab have been promising. We aim to quantify in better details the sinking ratio, colour variations and frost (H2O and/or CO2) depositions on CO2/MGS-1 samples under various setup conditions (illumination, material distribution). Using a hyperspectral device, we can measure the reflectance and simulate the CaSSIS signal in the different filters (PAN, NIR, RED, BLU) to compare to actual images that have been acquired during southern spring. 

How to cite: Cesar, C., Pommerol, A., Thomas, N., Portyankina, G., and Hansen, C. J.: Laboratory simulations of Martian Southern Spring : the outcome of CO2 cold jets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13204, https://doi.org/10.5194/egusphere-egu22-13204, 2022.

How to cite: Sokolowska, A., Thomas, N., and Wünnemann, K.: Impact cratering into water-covered targets on Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13476, https://doi.org/10.5194/egusphere-egu22-13476, 2022.

The observation of an eclipse of the Moon at millimetre wavelengths makes it possible to investigate the electrical and thermal properties of the lunar surface to a depth of 10 cm without being influenced by deeper layers. Such measurements are usually carried out with radio telescopes on Earth. When microwave instruments on weather satellites use observations of deep space for their calibration, however, the whole lunar disk appears sometimes in their field of view as well. We identified such an event with the Advanced Microwave Sounding Unit-B on NOAA-15 that coincided with a total lunar eclipse. From this unique vantage point in a polar orbit around the Earth we could measure, once per orbit, the lunar radiance at 183 GHz - a frequency, where the atmosphere is not transparent.

We found a maximum temperature drop during the eclipse of 47±9 K at 183 GHz, corresponding to 16.6±2.1% of the flux density of full Moon, and of 17.3±6 K, corresponding to 6.4±2.1% of the flux density of full Moon, for the window channel at 89 GHz. The evolution in time of the global flux agrees well with the predictions from a new radiative transfer model simulating the global brightness temperatures. Our measurements are consistent with results reported in the past, except for two, which we consider erroneous. The temperature changes are similar everywhere on the lunar disc. The good agreement between the observations from a weather satellite and theoretical predictions demonstrates that the Moon is very useful as flux reference and for checking the reliability of climate data records from Earth observation.

How to cite: Burgdorf, M., Liu, N., Buehler, S. A., and Jin, Y.: Observation of a Total Eclipse of the Moon at 183 GHz, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1276, https://doi.org/10.5194/egusphere-egu22-1276, 2022.

The lunar cratering record is used to constrain the bombardment history of both the Earth and the Moon. However, it is suggested from different perspectives, including impact crater dating, asteroid dynamics, lunar samples, impact basin-forming simulations, and lunar evolution modelling, that the Moon could be missing evidence of its earliest cratering record. Here we report that impact basins formed during the lunar magma ocean solidification should have produced different crater morphologies in comparison to later epochs. A low viscosity layer, mimicking a melt layer, between the crust and mantle could cause the entire impact basin size range to be susceptible to immediate and extreme crustal relaxation forming almost unidentifiable topographic and crustal thickness signatures. Lunar basins formed while the lunar magma ocean was still solidifying may escape detection, which is agreeing with studies that suggest a higher impact flux than previously thought in the earliest epoch of Earth-Moon evolution.

How to cite: Miljkovic, K., Wieczorek, M. A., Laneuville, M., Nemchin, A., Bland, P. A., and Zuber, M. T.: Large impact cratering during lunar magma ocean solidification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2214, https://doi.org/10.5194/egusphere-egu22-2214, 2022.

Lunar Laser Ranging (LLR) has been measuring the distance between the Earth and the Moon since 1969, where the measurements are provided by the observatories as Normal Points (NPs). The Institute of Geodesy (IfE) LLR model has (as of April 2021) 28093 NPs. Using the LLR observation equation, the LLR residuals (difference of observed and calculated values of the light travel time) are obtained for each NP. The LLR analysis procedure is an iteration of the calculation of ephemeris of the solar system followed by the calculation of residuals and the estimation of parameters using a Least-Squares Adjustment (LSA). The initial orbit of the Moon (Euler angles and angular velocity of the lunar mantle, Euler angles of the lunar core, and the position and the velocity of the selenocenter), amongst many other parameters, is estimated from the LSA. In our previous standard calculation, the initial orbit of the Moon was estimated for June 28, 1969 and ephemeris was calculated from this time until June 2022. In this study, we estimate the initial orbit of the Moon for Jan 1, 2000 to be able to benefit from the higher accuracy of the NPs over the timespan of LLR. The ephemeris is then calculated in forward and backward directions (until June 2022 and June 1969). When comparing the uncertainty obtained from a LSA of this study with the previous standard calculation, preliminary results show an improvement of over 50% in the initial position and the initial velocity of the Moon, a deterioration of about 20% in the Euler angles of the mantle and the core, and an improvement of over 15% in the angular velocity of the mantle. The changed analysis procedure will allow to compute a more accurate ephemeris for the upcoming years benefitting future lunar science. Recent results will be presented and major changes would be discussed.

Acknowledgement. This research was funded by Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy EXC 2123 QuantumFrontiers-390837967.

How to cite: Singh, V. V., Biskupek, L., Mueller, J., and Zhang, M.: Estimation of Lunar Ephemeris from Lunar Laser Ranging, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2815, https://doi.org/10.5194/egusphere-egu22-2815, 2022.

ESA and ROSCOSMOS’ Luna 27 mission will explore the south polar region of the Moon and will sample the lunar surface. To ensure the best samples are collected, which yield the greatest scientific return eight potential landing sites are being investigated using remote sensing methods. We have studied the safety of the eight potential landing sites by creating slope maps using the LOLA (30m/px) digital elevation model and classified slopes into safe areas (slopes <10°) and unsafe areas (slopes >10°). Additionally, we created slope maps classified in 2° intervals from 0-14° and greater than 14°, to further investigate which areas have the lowest slopes and therefore potentially the safest landing sites.

      We found that each of the eight landing sites contain areas that are safe for landing (slopes <10°) and sites 1, 2, 4, 6 and 8 contain large areas (>500 km²) that are classified as safe for landing. Site 3 has large craters with steep crater walls, which may present a hazard to landing. At site 5 there is a large crater (~20 km diameter) to the bottom right of the site, which has a steep crater walls and rim, which creates a topographic ridge in the south east of the landing site and should be avoided as a landing site. Site 7 also has a steep topographic ridge which again should be avoided as a landing area. In comparison site 8 contains a large area with shallow slopes in the center with slopes of 0-2°, which would be an ideal landing site. Site 1 covers a large crater (~40 km diameter), and the center of the crater floor has shallow slopes with less than 4°. Site 2 similarly has a large crater floor with slopes less than 4°. Both the crater floors of site 1 and site 2 could be a safe landing site.

     This initial investigation into the potential landing sites has identified areas which could be safe for landing Luna 27. Future work will use multiple datasets to explore the scientific potential of the landing sites including investigating the surface roughness, identifying craters and boulders, which could present a hazard to the lander, using thermal maps to measure the thermal stability, and exploring the illumination conditions and Earth visibility at each of the landing sites.

How to cite: Boazman, S., Heather, D., Sefton-Nash, E., Orgel, C., Houdou, B., Lefort, X., and Lunar Lander Team, T.: Investigating Potential Safe Landing Sites for ESA/ROSCOSMOS' Luna 27 Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5452, https://doi.org/10.5194/egusphere-egu22-5452, 2022.

   Chang’E-4 was the first mission to land a human object on the far side of the Moon. The landing site was at the Von Kármán (VK) crater at the South-Pole Aitken (SPA) basin, one of biggest craters in the solar system. SPA is believed that was created by a huge impact that penetrated the lunar crust and uplifted mantle materials. Evidence of these materials are expected to be found by the Yutu-2, the rover of the mission that is still active to this day, having covered more than 1km on the lunar’s surface. Yutu-2 is equipped with a stereo camera, visible/near-infrared imaging spectrometer, alpha particle x-ray spectrometer and Ground-Penetrating Radar (GPR). In-situ GPR is a powerful geophysical methodology with a uniquely wide range of applications to civil engineering, archaeology and geophysics. In planetary science, it was first used in 2013 during the Chang’E-3 mission. Since then, GPR has become a very popular instrument in planetary missions, and has been included in the scientific payload of Chang’E-4, E-5, Tianwen-1, and Perseverance. It is also planned to be used in the future missions Chang’E-7 (2024) and ExoMars (September 2022).

   Yutu-2 rover is equipped with three different GPR systems. One low frequency and two high frequency antennas. Unfortunately, due to interferences between the antenna and the metallic parts of the rover, the low frequency data have very low signal to clutter ratio making the interpretation of these data unreliable. On the other hand, the signal from the high frequency antennas is very clear, probably due the lack of ilmenite in the area, which results to low electromagnetic losses (compared to the Chang’E-3 landing site). This resulted to good quality radagrams that provided new insights into the structure and composition of the top ejecta layers at the VK crater.

    In the current paper, we introduce a complete processing scheme, tuned for high frequency lunar penetrating radar.  The first step of the proposed framework is an advanced hyperbola fitting (AHF) capable of inferring previously unseen layers due to their smooth boundaries. Subsequently, the reconstructed layered structure is used in a Reverse-Time Migration (RTM) coupled with Finite-Differences Time-Domain (FDTD) method. Via this approach, the radagram is focused subject to a 1D model, avoiding homogeneity constrains that often deviate from reality. Lastly, an un-supervised thresholding is applied to cluster the migrated image into two categories i.e. A) the background host medium and B) rocks/boulders. The suggested scheme is applied to the high frequency data collected by the Yutu-2 rover at the first 100 meters of the mission. A layered structure is inferred at the top 12 meters, similar to the results presented in [1]. Moreover, using the proposed RTM, an abundance of rocks/boulders was revealed. The distribution of the rocks/boulders correlates with the permittivity/density profile, indicating the reliability of the proposed scheme.   

References

[1] Giannakis, I., Zhou, F., Warren, C., & Giannopoulos, A. (2021). Inferring the shallow layered structure at the Chang’E-4 landing site: A novel interpretation approach using lunar penetrating radar. Geophysical Research Letters, 48, e2021GL092866

How to cite: Giannakis, I., Martin-Torres, J., Zorzano, M.-P., Warren, C., and Giannopoulos, A.: GPR Reverse-Time Migration for Layered Media: A Case Study at the Chang’E-4 Landing Site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7634, https://doi.org/10.5194/egusphere-egu22-7634, 2022.

Targeting the deployment of sustainable human and robotic exploration on the Moon by the end of this decade, there is a pressing need for better understanding the lunar water cycle and the availability of water for ISRU. The O-H isotope signatures in lunar water are key for determining the water origin in the Earth-Moon system and the mechanisms controlling water distribution and redistribution on the Moon. This has profound implications for understanding the Earth-Moon system’s history and the stability and renewability of water deposits.
Lunar volatiles are involved in a largely unconstrained and complex system of input, transport, trapping, recycling, and loss. The water origin on the Earth-Moon system remains poorly understood. The δD signatures from Apollo samples and meteorites suggest various contributing reservoirs of different origins for lunar water, and/or secondary processes [1], [2]. The different origins include: i) Magmatic (primordial) [3]; ii) asteroidal/cometary impacts [4], [5]; iii) solar wind H+ [1]; iv) mixed origin (solar wind H+/inclusion within meteorite impact glasses or volcanic glasses [6]).
The Roscosmos/ESA Luna 27 mission [7] is one of several international lunar polar missions for in-situ analyses of lunar surface, targeting pressing scientific and industrial knowledge gaps. To interpret the results derived from those polar missions it is critical to understand the extent and nature of any potential water ice loss and related isotope fractionation during the sampling chain.
Experimental studies on isotope fractionation during ice sublimation in nonequilibrium conditions are scarce. These studies concluded on different trends: i) no relevant isotope fractionation up to 40% ice mass loss [8], ii) relevant Rayleigh-like fractionation trend [9]. There is no kinetic isotope fractionation model (theoretical or experimental) for ice sublimation in low pressure systems at cryogenic temperatures, which considers the expected physical processes. Thus, the calculation of water ice isotope signatures remains highly uncertain, hindering the assessment of potential lunar water resources and the interpretation of scientific planetary data.
Here we present a theoretical isotope fractionation model derived from concepts developed by Criss (1999) [10] and adapted to the physical processes expected under lunar conditions, which will contribute to i) more robust interpretations of water ice behaviour in lunar environment and/or extra-terrestrial and/or extreme terrestrial environments; ii) mission operational planning, data processing, extraction/processing techniques; iii) exploration/exploitation roadmap, space mining business plan, natural resources management. [1] B. M. Jones et al., 2018. Geophys. Res. Lett., 45(20), 10,959-10,967; [2] F. M. McCubbin and J. J. Barnes, 2019. Earth Planet. Sci. Lett., 526; [3] A. E. Saal et al., 2013. Science, 340(6138), 1317–1320; [4] J. P. Greenwood et al., 2011. Nat. Geosci., 4(2), 79–82; [5] J. J. Barnes et al., 2016. Nat. Commun., 7(1), 11684; [6] C. I. Honniball et al., 2021. Nat. Astron., 5(2), 121–127; [7] D. J. Heather et al., 2021. Lunar Planet. Sci. Conf. LPI, Abstract #2111; [8] J. Mortimer et al., 2018. Planet. Space Sci., 158(Feb), 25–33; [9] R. H. Brown et al., 2012. Planet. Space Sci., 60(1), 166–180 [10] R. E. Criss, 1999. USA: Oxford University Press.

How to cite: López Días, V., Pfister, L., Hissler, C., and Barnich, F.: A more robust interpretation of water ice isotope signature from lunar polar missions: theoretical model for isotope fractionation during water ice sublimation in very low pressure systems at cryogenic temperatures., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8169, https://doi.org/10.5194/egusphere-egu22-8169, 2022.

Orbital magnetic field observations of the Moon show several magnetic anomalies distributed heterogeneously across its surface. These observations and results from paleomagnetic studies on lunar rocks corroborates that the lunar crust is locally magnetized. The origin of these magnetic field anomalies is still debated, as most of them are not related to known geological structures or processes. Some of the current suggestions to explain the origin of the anomalies sources include contamination from impactors that could deliver iron-rich material to the lunar surface, and heating associated with localized magmatic activity that could thermochemically alter rocks to produce strong magnetic carriers. Both hypotheses need however an inducing field to magnetize the lunar crust, and strong evidence from previous studies argues in favor of this being a global magnetic field generated by a core dynamo.

In this work, we aim to elucidate the origin of the magnetic anomalies by constraining the location and shape of the underlying magnetization. We do so by inferring the magnetization geometry from orbital magnetic field measurements using an inversion scheme that assumes unidirectional magnetization while making no a priori assumptions about its shape. This method has been used up to now to infer the direction of the underlying magnetisation but it has not yet been used to infer the geometry of the sources. We test the performance of the method by conducting a variety of synthetic tests using magnetized bodies of different geometries such as basins, dykes, and lava tubes, each corresponding to a different possible origin scenario for the observed magnetic anomalies.  Results from our synthetic tests show that the method is able to recover the location and shape of the magnetized volume. We explore how different input parameters, such as shape, depth, thickness, and field direction influence the method’s performance in retrieving the characteristics of the magnetized volume. Such an analysis can be performed on many lunar magnetic anomalies, including those which are not related to swirls or impact craters, i.e., the mechanisms that have been most studied up to now. This will help elucidate the geological history of the Moon and key features of the lunar dynamo evolution.

How to cite: Oliveira, J. S., Vervelidou, F., Wieczorek, M. A., and D. Michelena, M.: Constraints on the lunar magnetic sources location using orbital magnetic field data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8651, https://doi.org/10.5194/egusphere-egu22-8651, 2022.

Tidal response of the Moon provides crucial insight into the structure and rheology of the lunar interior (Williams et al. 2013). The body deformation subject to forces raised by external objects, most evidently Earth and the Sun, induces a variability of the gravitational field, which is characterized by the Love number, k. This effect may, in turn, manifest itself over time in the perturbed motion of orbiting spacecraft (Konopliv et al. 2013; Lemoine et al. 2013).

For an elastic body the response to the periodic excitation is instantaneous and relaxation times resulting in phase lags of the response are thus neglected. In reality, the lunar interior exhibits a degree of viscosity and dissipates energy through friction, in which case k not only varies with frequency but also comprises an imaginary part that represents a phase lag in tidal response (Williams et al. 2013).

Here, we investigate the signatures of the frequency-dependent Love number in the motion of a lunar orbiter. We formulate the problem following Williams & Boggs (2015), and focus on the variability of five Stokes' coefficients of the second degree effected by k2. The time-varying components are expanded at given characteristic frequencies associated with (linear combinations of) the Delaunay arguments. We make use of the Technical University Delft Astrodynamics Toolbox (Dirkx et al., 2019; https://tudat-space.readthedocs.io/) to investigate the orbit evolution of lunar orbiters, e.g., the Lunar Reconnaissance Orbiter (Mazarico et al. 2018), subject to the time-varying lunar gravitation. Meanwhile, we leverage the analytic theory of Kaula (1966) to illuminate the impact of such specific yet minute perturbations, especially non-short-period variations of the spacecraft orbit (Kaula 1964; Lambeck et al. 1974; Felsentreger et al. 1976).

A particular interest here is in the potential estimability of the frequency-dependent phase lag. Following Dirkx et al. (2016), we conduct a preliminary study of the sensitivity of spacecraft orbit adjustment to the said tidal effects. That is, we investigate if, under which conditions, and to what degree, the signals in question will be absorbed by the adjustment of initial states or other parameters, a consequence that will effectively prohibit the detection of the tidal effects. The outcome is expected to shed light on the minimum criteria of their estimation and thus instructive to real-world data analysis in the future.

Reference

Dirkx, D., et al. (2016), PSS, 134, 84-95
Dirkx, D., et al. (2019), Astrophysics and Space Science, 364:37
Kaula W.M. (1964), Reviews of Geophysics, 2, 661-685
Kaula W.M. (1966), Theory of Satellite Geodesy, Dover Publications, Inc.
Konopliv, A.S., et al. (2013), GRL, 41, 1452-1458 
Lambeck, K., et al. (1974), Reviews of Geophysics and Space Physics, 12, 412-434
Felsentreger, T.L. et al. (1976), JGR, 81, 2557-2563
Lemoine, F.G., et al. (2013), JGRP, 118, 1676-1698
Mazarico, E., et al. (2018), PSS, 162, 2-19
Williams J.G., et al. (2013), JGRP, 119, 1546-1578
Williams J.G., and Boggs, D.H. (2015), JGRP, 120, 689-724

How to cite: Hu, X., Stark, A., Dirkx, D., Hussmann, H., Fienga, A., Fayolle-Chambe, M., Melini, D., Spada, G., Mémin, A., Rambaux, N., and Oberst, J.: Sensitivity analysis of frequency-dependent visco-elastic effects on lunar orbiters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9722, https://doi.org/10.5194/egusphere-egu22-9722, 2022.

Lunar Gravitational-wave Antenna (LGWA) proposes to deploy an array of high-end seismometers on the surface of the Moon. The LGWA network will measure the lunar surface displacement excited by Gravitational waves (GWs) with a targeted observation band of 1mHz – few Hz.   Seismic noise in that frequency band is very low due to the absence of atmosphere and oceans, representing the main inherent advantage that makes the Moon an ideal target for a GW detection experiment. 

The scientific and technical challenges of LGWA are diverse.  Since its initiation, LGWA has relied on experts from fundamental physics, astrophysics, geophysics, engineering, and planetary science. 

The collaboration is currently organized in working groups (WGs) to cover five key themes: GW science, lunar science, payload, deployment, and operations.  

At the beginning of 2022, we started the activities of WG2 to assess the current knowledge of the lunar environment. We aim to characterize and develop models of deployment scenarios suitable for LGWA sensors, via a multi-pronged approach of data analysis and on-field experiments probing terrestrial analogs of lunar terrains. 

Besides characterizing the lunar seismic background noise, other goals of the group are related to modeling the lunar interior structure as well as Moon’s normal modes. These will be further used to develop a model of the interaction between the Moon and GWs. The knowledge about the displacement level of this excitation and the background noise will be used to define novel techniques for background noise reduction.

For this purpose, WG2 is composed of physicists, engineers, geophysicists, and geologists. For our activities, we chose an interdisciplinary approach that requires initial communication efforts to create a common ground that will evolve into a crucial baseline activity for the whole LGWA project.

Here we will report our progress in the first months of the activity of our collaboration.     

How to cite: Frigeri, A., Olivieri, M., Harms, J., Bonforte, A., Giunchi, C., Komatsu, G., Majstorović, J., Massironi, M., and Melini, D.: The Moon Science Working Group of the Lunar Gravitational-Wave Antenna Project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10171, https://doi.org/10.5194/egusphere-egu22-10171, 2022.

Mons Hansteen Alpha is a lunar ‘red spot’ that is now considered to be of non-mare volcanic origin. In addition to being characterized by an evolved silicic composition, Mons Hansteen Alpha is also of interest because of the presence of Mg-spinel exposures in association with the siliceous lithology, as detected by the Moon Mineralogy Mapper on board the Chandrayaan-1 mission. The Compton-Belkovich volcanic complex on the Moon is the only other established example of this kind. The origin of Mg-spinel exposures on the lunar surface is considered to be either impact related or endogenic. Models have been proposed in earlier studies to explain the spinel exposures on anorthosites, and spinel in association with other mafic minerals such as olivine and orthopyroxene. However, the origin of Mg-spinel exposures within an evolved siliceous body that has very limited associated mafic minerals is yet to be fully explored. In this study, the Mg-spinel exposures on Mons Hansteen Alpha were analyzed using high resolution LROC NAC images and correlated with topographic information from the SLDEM data. These investigations suggest that in most cases, the spinel exposures on Mons Hansteen are not related to any impact related structures. The exposures are often found on elevated features such as ridges, or around irregular-shaped pits. The distribution of the exposures is mostly limited to the Pitted unit, the youngest unit in the volcanic structure; this favours an endogenic origin instead of one related to impact as otherwise, the exposures would also have been distributed in the other units. On the bases of these observations, it is suggested that the Mg-spinel exposures on Mons Hansteen Alpha are endogenic in nature. A model is proposed for the origin of endogenic Mg-spinel exposures on silicic volcanic structures. For this, model reactions were considered between a lunar picritic basaltic magma and two types of crustal protoliths- (i) a mixture of silica and anorthosite and (ii) a lunar monzogabbro. The modelling has been done using the alphaMELTS 2 software. The proposed model combines the crustal melting model for the genesis of silicic volcanic structures with a genetic model for the Mg-spinel exposures. The mixture of silica and anorthosite has been considered as a possible crustal protolith consistent with recent experimental lunar magma ocean (LMO) crystallization models that crystallized silica as one of the end stage products. On the other hand, earlier studies have proposed monzogabbro as a possible protolith composition for lunar silicic lithology. The models demonstrate the possible pathways of forming silicic compositions similar to the lunar granite samples collected during the Apollo missions, with simultaneous crystallization of Mg-spinel.

How to cite: Moitra, H. and Gupta, S.: Investigating the origin of Mg-spinel exposures on Mons Hansteen Alpha, an evolved silicic volcanic structure on the Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10274, https://doi.org/10.5194/egusphere-egu22-10274, 2022.

Understanding whether the Moon had a long-lived magnetic field is crucial for determining how the lunar interior and surface evolved, and in particular for assessing whether a paleomagnetosphere shielded the regolith. Magnetizations from some Apollo samples have been interpreted as records of a global lunar magnetic field between approximately 4.2 and 1.5 Ga that would have created shielding, but the inferred paleofields are too strong and continuous to be generated by the small lunar core. Moreover, vast areas of the lunar crust lack magnetic anomalies that should mark the past presence of a dynamo. New paleointensity data from an Apollo impact glass associated with a young 2 million-year-old crater records a strong Earth-like magnetization, providing evidence that impacts can impart intense signals to samples recovered from the Moon, and other planetary bodies (Tarduno, Cottrell, Lawrence et al., Science Advances, 2021). This observation provides motivation for future lunar collections to constrain impact size - magnetization scaling relationships. Moreover, new data from silicate crystals bearing magnetic inclusions from Apollo samples formed at 3.9, 3.6, 3.3, and 3.2, Ga are capable of recording strong core dynamo-like fields but do not, indicating the lack of a global magnetic field (Tarduno, Cottrell, Lawrence et al., Science Advances, 2021). Together, these new data indicate that the Moon did not have a long-lived core dynamo. As a result, the Moon was not sheltered by a sustained paleomagnetosphere, and the lunar regolith should hold buried 3He, water, and other volatiles resources acquired from solar winds and Earth’s magnetosphere over some 4 billion years. These findings highlight the opportunity to learn about the evolution of the solar wind and Earth’s earliest atmosphere during future lunar exploration. This could in turn provide key data to better understand how Earth evolved as a habitable planet despite the expected extreme solar forcing during its first billion years (Tarduno, Blackman, Mamajek, Phys. Planet Inter., 2014).

How to cite: Tarduno, J.: Absence of a long-lived lunar paleomagnetosphere and opportunities for future exploration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10400, https://doi.org/10.5194/egusphere-egu22-10400, 2022.

Many moons of the Solar System, e.g. the Galilean satellites or Earth’s Moon, are subject to strong tidal deformations. Measurements of the tidal Love number h2 by laser altimeters from orbiting spacecraft may provide crucial constraints on their interior structures and rheology. Using precise observations by laser altimeters estimates for h2 were obtained for the Moon (Mazarico et al. 2014, Thor et al., 2021) and Mercury (Bertone et al., 2021), and are planned for Ganymede (Steinbrügge et al., 2015). Typically, height differences at crossing points of laser profiles, so called crossover points, are used for such measurements (Mazarico et al. 2014, Bertone et al., 2021). However, a new method based on simultaneous inversion of tidal deformations and global topography has recently been demonstrated (Thor et al. 2021) using data from the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO).

Here we propose the refined “self-registration” method, which makes use of an accurate reference digital terrain model (DTM) constructed from the laser profiles themselves. This DTM is obtained by iteratively co-registering random subsets of laser profiles to an intermediate DTM produced by the other profiles. With our method we are not limited to profiles that are actually crossing themselves and can obtain height difference between all available profiles. Moreover, we can overcome the interpolation error at the crossover points as we use the entire profile with all its data points to measure the relative height differences. This method was recently successfully applied to measure the seasonal change of the ice/snow level in polar regions of Mars using Mars Orbiter Laser Altimeter (MOLA) data (Xiao et al., 2021).

In order to validate our method and assess its performance we perform a simulation of a tidal signal in the LOLA data with an assumed value for the tidal Love number h2 of the Moon. Thereby the height measurement at the location of the LOLA footprint is derived from a DTM and an artificial tidal signal applied on it. Thereby, we consider viscoelastic effects on the tidal deformation and different tidal frequencies. With the help of these simulations we assess the accuracy of the h2 measurement and check the sensitivity to the measurement of the tidal phase lags.

References:

Mazarico et al. (2014). Detection of the lunar body tide by the Lunar Orbiter Laser Altimeter. GRL, 41(7), 2282-2288. doi:10.1002/2013GL059085

Thor et al. (2021). Determination of the lunar body tide from global laser altimetry data. JoG, 95(1). doi:10.1007/s00190-020-01455-8

Bertone et al. (2021). Deriving Mercury Geodetic parameters with Altimetric Crossovers from the Mercury Laser Altimeter (MLA). JGR-Planets, 126(4), e2020JE006683. doi:10.1029/2020JE006683

Xiao et al. (2021). Prospects for Mapping Temporal Height Variations of the Seasonal CO2 Snow/Ice Caps at the Martian Poles by Co-registration of MOLA Profiles. Under review in PSS, https://arxiv.org/abs/2109.04899

How to cite: Stark, A., Xiao, H., Hu, X., Fienga, A., Hussmann, H., Oberst, J., Rambaux, N., Mémin, A., Briaud, A., Baguet, D., Spada, G., Melini, D., and Saliby, C.: Measurement of tidal deformation through self-registration of laser profiles: Application to Earth’s Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10626, https://doi.org/10.5194/egusphere-egu22-10626, 2022.

While the origin of lunar polar volatiles remains an open question, their most likely sources are volcanic outgassing or volatile-rich impactors. Both such sources are sporadic in nature and are characterized by release of large amounts of volatiles over a short period of time and long periods of repose between such events. If a sufficient amount of volatiles was generated in such a delivery event, a transient collisional atmosphere could form. Such an atmosphere, if it persists for a long enough time, would protect certain volatiles (like water) from photodissociation and escape to space and would promote their transport to the polar cold traps where they could be stored and preserved for billions of years. Hence, such transient atmospheres could have a significant impact on the distribution and abundance of volatiles currently observed on the Moon. Here we study such a hypothetical atmosphere that could have been formed due to volcanic outgassing during the peak of lunar volcanic activity at ~3.5 Ga and investigate its longevity, climatology and effect on volatile transport.

We employ the ROCKE-3D [1] planetary climate model to simulate processes in a volcanically-induced lunar atmosphere. We use orbital and radiation parameters corresponding to conditions at 3.5 Ga (17.8 days rotation period and a solar constant 75% of the modern value). For most experiments we use zero obliquity, though we investigate the effect of non-zero obliquity on atmospheric stability and volatile transport. We assume a CO₂-dominated atmosphere in accordance with predictions of our chemistry model [2]. For the atmospheric thickness we follow the argument of Head et al. [3] that due to long periods of repose between the volcanic events the atmosphere would not accumulate above the pressure of a few microbars, and thus we limit our parameter space to a range of 1 microbar to 1 mb surface pressures. To investigate the ability of such an atmosphere to transport volatiles we set up a typical volcanic eruption experiment [4] and follow the fate of the outgassed water.

In most of our experiments the atmosphere was stable, though in some cases a small non-zero obliquity (a few degrees) was needed to prevent a collapse due to CO₂ condensation at the poles. We found that even very thin atmospheres were efficiently transporting volatiles to the poles. The efficiency of transport sometimes was higher for thinner atmospheres, most likely due to a stronger circulation cell. We also found that water transport efficiency depended on initial conditions at the surface. A water-free dry surface suppressed re-evaporation, thus reducing the total flux of outgassed water to the poles. But even in the case of dry soil, water transport was efficient with 19% of outgassed water delivered to the poles in just a few months (for the 10 microbar atmosphere).

References: [1] Way M. J. et al. (2017) ApJS, 231, 12. [2] Aleinov I. et al.  (2019) GRL, 46, 5107–5116. [3] Head J. W. et al. (2020) GRL, 47, e2020GL089509. [4] Wilson L. and Head J. W. (2018) GRL, 45, 5852-5859.

How to cite: Aleinov, I., Way, M., Head, J., Tsigaridis, K., Harman, C., Wolf, E., Gronoff, G., Varnam, M., and Hamilton, C.: Effect of Volcanically-Induced Transient Atmospheres on Transport and Deposition of Lunar Volatiles., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10764, https://doi.org/10.5194/egusphere-egu22-10764, 2022.