EGU General Assembly 2023  

Early studies of “geo-magnetism” dealt with the understanding of long-term developments and short-term disturbances in the geo-magnetic field as measured by magnetometers on ground level. Soon after the IGY the concept of several co-existing and globally or locally interacting ionospheric current systems (DP1 & 2) was born. Both systems seemed to respond differently to solar wind driving conditions and internal magnetospheric processes. Through continued global international study efforts, like e.g. the International Magnetospheric Study (IMS) and later the International Solar Terrestrial Physics program (ISTP) the 2-dimenional monitoring of geomagnetic “disturbances”, now understood as complex signatures of different current systems within and beyond the upper atmosphere, became a powerful tool to monitor and study the complicated three-dimensional coupling of the magnetosphere to the upper atmosphere and its ultimate relation to certain solar wind drivers of magnetospheric conditions.

Geomagnetic observations, both globally and regionally, are today a valuable asset to put the very local measurements of magnetospheric satellites (even if “multi-point”) into its proper context with respect to the dynamics of the magnetosphere. The ultimate goal of such measurements today is not only to identify the energy and activity state of the magnetosphere as such, but also to study the exact location, strength and spatio-temporal development of the most powerful short-lived magnetic disturbances that we know, the so-called magnetospheric substorms and the closely related intensifications of major magnetic storms.

The study of the physics of the geo-space environment in response to solar activity and solar wind driving has over the last twenty years matured to make first useful predictions of a large variety of plasma processes in near-Earth space, which have the potential to detrimentally affect human space exploration and human technological infrastructure both on ground and in space. The fast-growing research and operational field of Space Weather has stimulated new active research (including advanced model efforts) to get to the bottom of some of the most effective geo-space plasma phenomena, and to understand the variability of ionospheric currents, and their connection to the outer magnetosphere. This is at present one of the most intriguing scientific problems in the field of Space Weather. Potentially any conducting infrastructure on the ground can be detrimentally or catastrophically affected by fast changes in the magnetic field (dB/dt) via geomagnetically induced currents (GICs). In parallel, the involved ionospheric current systems can cause further secondary impacts on space-borne communication and navigations systems via ionospheric plasma instabilities and atmospheric drag effects on satellite orbits.

In my presentation I will give a short background to the historical progress of space science with the help of magnetometer data, and then highlight a selection of recent research topics, where global and regional magnetometer networks (together with a multitude of dedicated space missions) represent a very important part of the systematic and coordinated study of the near-Earth plasma environment, the coupled solar wind - magnetosphere - ionosphere – atmosphere “System of Systems”.

How to cite: Opgenoorth, H.: From Geomagnetism and Space Science to Space Weather, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8054, https://doi.org/10.5194/egusphere-egu23-8054, 2023.

Coronal holes (CH) are large, long-lived structures commonly observed in the solar corona as regions of reduced emission in EUV and X-ray wavelengths. They feature a characteristic open magnetic field configuration along which ionized electrons and atoms are accelerated into the interplanetary space. The resulting outflowing plasma is called high seed solar wind stream (HSS; see Cranmer 2009 and references therein). These HSSs are the major cause of minor to moderate geomagnetic activity at Earth (see Richardson 2018 and references therein).

To be able to predict the arrival and impact of those disturbances accurately, their origin and evolution need to be studied in detail. And to do so, it is imperative that CHs are accurately and reliably extracted, thus leading to the development of the Collection of Analysis Tools for Coronal Holes (CATCH). By using the intensity gradient across the CH boundary, it is possible to robustly extract CHs whose properties can then be analyzed. We find that the area of long-living CHs generally evolves by growing to a maximum before decaying. However, the associated magnetic field does not evolve equally. Depending on the CH, we find a correlation, an anti-correlation or even no correlation over the course of its lifetime. Therefore, we believe that the evolution of a CHs magnetic field is primarily driven by the large-scale connectivity changes in the Sun's global magnetic field. Further, we find that the plasma properties within CHs show a significant center to boundary gradient, which may justify the distance-to-boundary parameter used in some solar wind modeling.

To study the evolution of CHs in detail, a 360° view of the Sun is necessary; however, the magnetic far-side of the Sun still eludes. The few snapshots with Solar Orbiter provide only a fragmented picture of the magnetic field on the solar far-side. We found that by using EUV observations of the transition region (specifically using Stereo) it is possible to estimate the magnetic field density of CHs on the solar far side. In addition, we are currently investigating the incorporation of helioseismic observations into synoptic magnetograms to generate a maps that show the magnetic field of the whole Sun at a given time.

How to cite: Heinemann, S. G.: On the evolutionary aspects of solar coronal holes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8687, https://doi.org/10.5194/egusphere-egu23-8687, 2023.

We use the Magnetospheric Multiscale mission to observe electron acceleration events at Earth’s quasi-perpendicular bow shock. Acceleration mechanisms up to mildly relativistic electron energies are investigated in order to provide more insight into the long-standing injection problem. The events are chosen for their diversity in observed high energy electron flux and shock angle, θ_Bn, enabling the Stochastic Shock Drift Acceleration theory to be further tested for different shock parameters. An alternative acceleration mechanism is also presented. The electron acceleration region of this unusual event is associated with a decrease in wave activity, inconsistent with common electron acceleration mechanisms such as Diffusive Shock Acceleration and Stochastic Shock Drift Acceleration. The energetic electron population is shown to have a bi-directional pitch-angle distribution, indicating parallel heating along the magnetic field lines.
We propose a two-step acceleration process where energetic field-aligned electrons originating from the electron foreshock act as a seed population further accelerated by a shrinking magnetic bottle process. Furthermore, we present evidence for electron pitch-angle scattering at the shocks and discuss its importance and different roles for the different electron acceleration mechanisms mentioned above.

How to cite: Lindberg, M., Vaivads, A., Raptis, S., and Karlsson, T.: Electron acceleration mechanisms at Earth’s quasi-perpendicular bow shock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-375, https://doi.org/10.5194/egusphere-egu23-375, 2023.

Reliable data on the range and distribution of solar granulation size are essential for modeling plasma convection, studying the magnetic activity cycle, and measuring the Sun's global parameters. Most known morphometric studies of solar granulation measure and document mean area or equivalent diameter of granules from high-resolution optical image time series. One of the main shortcomings of these studies is that the mean area or equivalent diameter cannot represent the characteristic scale of granular cells due to the skewed size distribution. The measured mean granular size is particularly susceptible to the influence of outliers due to occasional irregularities in image time series, unsuitable image quality, e.g. local blurring, and errors in automatic image processing. The lack of consolidated analytical formulations linking changes in granulation size to global solar variability complicates verification of empirical results. It is significant that over the last 70 years the observed value of the relative changes in the average size of granular cells associated with the solar magnetic cycle has declined by an order of magnitude from 20% to 2%.

In this study, we introduce the normalized version of the mean granular area, called the mean extent, which is defined as the area of a granular cell divided by the area of the smallest bounding box enclosing the cell, with averaging over all cells in the observation frame. In contrast to other known granulation properties, the proposed dimensionless parameter has a normal distribution, is less scattered and invariant to scaling effects, e.g. because of defocus. We write some basic expressions for the relative variation in granulation extent and determine the magnitudes of the relative changes in the horizontal size of granular cells due to variations in global solar parameters. We define that the total number of granular cells and their mean size decrease while the solar radius, effective temperature, luminosity and granulation time scale increase with increasing sunspot area.

The specific behavior of mean extent versus mean area and contrast of granular cells was tested using Hinode image sequences obtained in the blue continuum channel with a 27- and 1-day cadence over descending and ascending phases of the 24th activity cycle, and compared to corresponding sunspot indices. The consistent 14- and 378-day delays in the cause-and-effect relationship between sunspot number and granulation scale were revealed in the daily and synoptic time series, respectively, and explained by rotational effects. Remarkably, the mean granular extent varies in phase with the sunspot indices; its long-term average was measured at 0.65, which corresponds to the predominantly hexagonal shape of the granular cells. Higher values of granular extent indicate regularization and compaction of the granulation pattern in both quiescent and active regions. We conclude that the mean size and extent of granular cells measured at the center of the disk could become a reliable index of solar convection and a reactive indicator of global magnetic activity, although the mean granulation size in polar regions remains somewhat uncertain, worthy of further study with high-resolution optical data from extra-ecliptic missions.

How to cite: Sharov, A. and Hanslmeier, A.: Relative variation of granulation size as a function of global solar parameters , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1378, https://doi.org/10.5194/egusphere-egu23-1378, 2023.

Coronal mass ejections (CMEs) are the major eruptive phenomena that cause various space weather effects. CMEs can be deflected by coronal holes (CH) away or towards the Sun-Earth line depending on their relative location, and also the high speed streams from CH can influence CME propagation. Coronal dimmings which are away or toward the CH may also cause CME deflection. The main aim of our study is to analyse the deflection/rotation of CMEs by tracking them in COR1 and COR2 field of view of STEREO onboard SECCHI with the help of 3D reconstruction Graduated cylindrical shell (GCS) model. We analyse 60 Earth-directed CMEs and their associated low coronal signatures observed in SDO/AIA. In addition, with the help of CATCH tool we study the nearby coronal hole parameters. Furthermore, we analyze the associated coronal dimmings by considering the movement of secondary dimmings towards or away the nearby CH. Out of 60 events, 31 events show deflection/rotation, as we track them from 1.76R_☉ to 20.8R_☉. A small fraction of (11%) events show deflection in longitude, and a significant fraction of events show deflection in latitude (38%) and rotation (40%). We discuss these results with respect to the vicinity and direction of coronal holes.

How to cite: Karuppiah, S., Dumbovic, M., Martinic, K., Temmer, M., Veronig, A., Chikunova, G., Podladchikova, T., Dissauer, K., Heinemann, S., and Vrsnak, B.: Deflection/Rotation of Earth-directed CMEs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1395, https://doi.org/10.5194/egusphere-egu23-1395, 2023.

Neutral atoms from the interstellar medium around the Sun enter the heliosphere unimpeded by the electromagnetic fields. They bring information about the properties of our interstellar neighborhood, processes at the boundary between the solar and interstellar media, and the direction of the Sun’s motion in the Galaxy. The interstellar neutral atoms of hydrogen, deuterium, helium, neon, and oxygen reach close distances to the Sun where they are probed either by direct detection or remote sensing methods. Here we focus on a direct measurement technique for interstellar neutral atoms of energies from 10 eV to 1 keV on an example of the instruments onboard the Interstellar Boundary Explorer (IBEX) and the follow-up mission the Interstellar Mapping and Acceleration Probe (IMAP, to be launched in 2025). IBEX continuously collects interstellar neutral atom data from the beginning of its operation in 2008 providing a survey over the Solar Cycle 24 despite its observation season being limited during the year. IMAP tracks the beam of interstellar neutrals in the sky throughout the year, which significantly expands scientific opportunities for probing interstellar neutrals from close distances to the Sun. We present the greatest accomplishments of interstellar neutral atom research enabled by IBEX and discuss the science goals in this area for IMAP.

The results are presented in collaboration with scientists and researchers at Southwest Research Institute, the University of Bern, the University of New Hampshire, and Princeton University.

How to cite: Sokol, J. M.: Interstellar Neutral Atom Measurements with IBEX and IMAP, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1427, https://doi.org/10.5194/egusphere-egu23-1427, 2023.

How to cite: Hu, H., Liu, Y. D., Chitta, L. P., Peter, H., and Ding, M.: Spectroscopic and Imaging Observations of Spatially Extended Magnetic Reconnection in the Splitting of a Solar Filament Structure, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1508, https://doi.org/10.5194/egusphere-egu23-1508, 2023.

The kappa distribution is one of the most important velocity distributions in space plasmas. It has both a quasi-Maxwellian core and a suprathermal tail, and it has been considered throughout the heliosphere and magnetospheres. Despite a strong demand for numerical studies in a kappa-distributed plasma, it is not clear how to generate kappa distributions in particle velocities in particle-in-cell (PIC) and Monte Carlo simulations. In this contribution, we present numerical procedures to generate three kappa-type velocity distributions in particle simulations.

First, we review an algorithm for the nonrelativistic kappa distribution. Mathematically, the kappa distribution is equivalent to the multivariate t-distribution [1]. A random variate following the multivariate t-distribution can be generated from the normal and chi-squared distributions. Second, we propose algorithms to generate a kappa loss-cone (KLC) distribution [2], which is often considered in the planetary magnetosphere. We have constructed two procedures. Using the mathematical properties of the beta prime distribution, we can straightforwardly generate the KLC distribution in particle simulations. Third, we propose a procedure for initializing a relativistic kappa distribution. Although the Lorentz factor makes this problem difficult, we have successfully developed a rejection-based algorithm [3]. The rejection part extends an earlier method for a relativistic Maxwell distribution [4], and it accepts particles at the rate of 95% or higher. Our method also use the beta prime distribution. As a result, we can successfully generate a power-law tail of the relativistic kappa distribution.

References:
[1] R. F. Abdul & R. L. Mace, Phys. Plasmas 22, 102107 (2015)
[2] D. Summers & R. M. Thorne, J. Plasma Phys. 53, 293 (1995)
[3] S. Zenitani & S. Nakano, Phys. Plasmas 29, 113904 (2022)
[4] E. Canfield, W. M. Howard, & E. P. Liang, Astrophys. J 323, 565 (1987)

How to cite: Zenitani, S. and Nakano, S.: Loading kappa-type distributions in particle simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1629, https://doi.org/10.5194/egusphere-egu23-1629, 2023.

The CCOR-1 will monitor our Sun’s Coronal Mass Ejections (CMEs).  It will reside on the Sun-Pointing Platform (SPP) of the Geostationary Operational Environmental Satellite (GOES) -U in a geostationary orbit.  As a member of the GOES-R Series of satellites, GOES-U will provide advanced imagery and atmospheric measurements of Earth’s weather, oceans and environment, real-time mapping of total lightning activity, and as well as monitoring of solar activity and space weather. GOES-U is the final satellite in the GOES-R Series, with an expected launch date in April of 2024. 

The Compact Coronagraph (CCOR) instrument was designed, built, and tested by the United States Naval Research Laboratory. CCOR-1, the first in a series of coronagraphs, is funded by the National Oceanic and Atmospheric Administration (NOAA), is managed by the National Aeronautics and Space Administration (NASA), and will ultimately be operated by NOAA.  Using a series of images of the Sun’s coronal white-light, scientists at NOAA’s Space Weather Prediction Center (SWPC) and National Centers for Environmental Information (NCEI) can determine the size, velocity, and density of these CMEs.  This information can then be used to assess and prepare for potential impacts of these solar storms on infrastructure here on Earth, as well as assets in space. 

CCOR-1 has completed instrument-level Integration and Testing (I&T), delivered to the GOES-U satellite integrator and is now mechanically integrated with the spacecraft. The integrated GOES-U satellite has completed Spacecraft-level Thermal Vacuum testing and is expected to complete all the remaining Spacecraft I&T activities by the EGU Conference date.

This paper presents the details on the CCOR-1 instrument, its integration onto the GOES-U satellite bus, and the expected performance.

How to cite: Dudley, R., Krimchansky, A., Tadikonda, S., Thernisien, A., Baugh, R., and Carter, M.: Compact Coronagraph (CCOR) Accommodation on GOES-U, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1714, https://doi.org/10.5194/egusphere-egu23-1714, 2023.

Traditional approaches to tracking solar outflows for space weather forecasting rely primarily on coronagraph images, which generally observe the solar corona above a minimum height of about 2.5 solar radii. EUV images have been widely used to characterize features on the solar disk, but the limited fields of view of most current EUV imagers have prevented their use for tracking outflows through the inner and middle coronae. A series of off-point campaigns with the GOES 16-18 Solar Ultraviolet Imager (SUVI) between 2018 and 2022 from three Flight Models have provided an opportunity to assess the value of extended EUV images for space weather forecasting applications. These new results demonstrate that wide field-of-view EUV images are useful for characterizing the early onset of eruptive events and tracking smaller outflow into the solar wind. They also reveal the origins of shocks that are known to accelerate particles and drive solar energetic particle (SEP) events. Because CMEs generally experience the bulk of their acceleration below the height of white light coronagraphic observations, these images provide information about the origins of these events that has not been available traditionally. Together with coronagraphic measurements, EUV images provide the continuous views needed to connect CMEs back to their source regions. Here, we present these new SUVI observations and discuss their potential use in space weather operations.

How to cite: Tadikonda, S. K., Seaton, D. B., Bethge, C., Caspi, A., Dahya, M., DeForest, C., Garhart, M. P., Hughes, J. M., Krimchansky, A., Sullivan, P. C., Todirita, M., and West, M.: From the Solar Limb and Out: Results from the Wide-Field EUV Image Campaigns with GOES/SUVI, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1807, https://doi.org/10.5194/egusphere-egu23-1807, 2023.

The heliosphere surrounding our solar system is formed by the interaction between the solar wind and the local interstellar medium as the Sun moves through interstellar space. With dimensions on the order of hundreds to potentially thousands of au, it is difficult to determine the 3D structure of the heliosphere and the properties of the plasma surrounding it. However, observations of energetic neutral atoms (ENAs), which are created as a product of charge exchange between interstellar neutrals and energetic plasma ions, allow us to remotely discern the properties of the distant heliospheric boundaries.

NASA's Interstellar Boundary Explorer (IBEX) mission, a small explorer spacecraft which has been measuring ENA fluxes at ~0.5-6 keV for more than a solar cycle, discovered a “ribbon” of enhanced ENA fluxes forming a narrow, circular band across the sky. While it is generally believed that the ribbon is formed from secondary ENAs from outside the heliopause, a source of ENAs that is separate from the globally distributed flux (GDF) across the sky, it is not clear exactly how the parent ions outside the heliopause evolve over time before they become ribbon ENAs. To help solve this issue, we present recent developments in modeling the evolution of the ribbon over a solar cycle, under different pitch angle scattering assumptions. We hypothesize that simulating the evolution of the ribbon under differing scattering rates may help discern the physical mechanisms responsible for creating the ribbon observed by IBEX. We compare our modeling results to IBEX data where the ribbon was separated from the GDF using spherical harmonic decomposition, analyzing the evolution of the ribbon’s intensity and geometry as a function of ENA energy.

How to cite: Zirnstein, E., Swaczyna, P., Dayeh, M., and Heerikhuisen, J.: Constraints on the IBEX Ribbon's Origin from its Evolution over a Solar Cycle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2095, https://doi.org/10.5194/egusphere-egu23-2095, 2023.

This talk provides an overview of the Interstellar Mapping and Acceleration Probe (IMAP), what we hope and expect to learn from it, and where we are in the development of the mission. IMAP is currently in Phase C and is slated to launch in early 2025. IMAP simultaneously investigates two of the most important and intimately coupled research areas in Heliophysics today: 1) the acceleration of energetic particles and 2) the interaction of the solar wind with the local interstellar medium. IMAP’s ten instruments provide a complete set of observations to simultaneously examine the particle injection and acceleration processes at 1 AU while remotely dissecting the global heliospheric interaction and its response to particle populations generated through these processes. For more information about IMAP, see McComas, D.J. et al., Interstellar mapping and acceleration Probe (IMAP): A New NASA Mission, Space Science Review, 214:116, doi:10.1007/s11214-018-0550-1, 2018.

How to cite: McComas, D.: Update on the Interstellar Mapping and Acceleration Probe (IMAP) Mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2100, https://doi.org/10.5194/egusphere-egu23-2100, 2023.

The physical mechanisms by which solar prominences (or filaments) form are still not well understood. The presently favored scenario invokes the evaporation of chromospheric plasma via localized heating at the footprints of a magnetic flux rope (MFR) or sheared arcade, and the subsequent condensation of this plasma in the corona due to thermal non-equilibrium (TNE). This scenario has been modeled extensively in one-dimensional (1D) hydrodynamic simulations along static magnetic field lines, and recently also in fully 3D magnetohydrodynamic (MHD) simulations, using idealized MFR configurations. However, such configurations lack the complexity of real prominence magnetic fields. In this presentation, we first briefly discuss our prominence modeling approach for the case of an idealized 3D MFR configuration. We then report on our recent attempts to employ data-constrained MHD simulations to model the formation of observed filaments. To this end, we selected the filament that erupted in a spectacular manner on June 7, 2011 in NOAA AR 11226. To model its formation, we first develop a semi-realistic ("thermodynamic MHD") model of the solar corona, using SDO/HMI data as boundary condition for the magnetic field. Next, we insert an MFR constructed with the RBSL method (Titov et al., 2018) into the source region of the filament. Finally, we impose localized heating at the MFR's footprints. We compare our results with our idealized simulations and discuss the challenges that arise once realistic cases are considered.

How to cite: Torok, T., Mason, E. I., Downs, C., Lionello, R., and Titov, V. S.: 3D MHD Modeling of an Observed Solar Prominence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2300, https://doi.org/10.5194/egusphere-egu23-2300, 2023.

Energetic particles represent an important component of the plasma in the heliosphere. Spacecraft observations have detected energetic particles accelerated at impulsive events in the solar corona and at interplanetary shocks. Fluctuations in energetic particle fluxes are related to solar activity and to magnetic turbulence in the interplanetary medium. Thanks to in-situ satellite observations, numerical simulations, and theoretical models, our knowledge on the particle acceleration processes involved has advanced significantly in recent years. Here we review new developments on particle acceleration at collisionless shocks, in particular in relation with the transport properties of supra-thermal particles, as inferred from the analysis of particle fluxes, addressing that anomalous, superdiffusive transport is common in the interplanetary medium. A link between the results obtained from the in-situ diagnostic, used for studying energetic particle transport and acceleration, and remote observations of astrophysical shocks will be discussed.

How to cite: Perri, S.: Recent advancements on particle acceleration at collisionless shocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2360, https://doi.org/10.5194/egusphere-egu23-2360, 2023.

The dynamics of small (few hundred nm) charged interstellar dust particles entering the heliosphere is affected by the heliospheric magnetic field and in particular by the heliospheric current sheet. To estimate the flux distribution of the dust particles inside the heliosphere we simulate numerically the trajectories of moderately large samples (10^4 particles) of small charged dust grains with starting points outside the heliopause. The simulations are repeated for different choices of the initial time. We use the semi-analytical model of the heliosphere that combines a simplified time-stationary description of the plasma flow in the heliosphere and the outer heliosheath with the time-dependent magnetic field carried passively by the flow. The form of the heliospheric current sheet is determined by our choice of the time-dependent magnetic polarity structure at the surface of the rotating Sun. 

How to cite: Mann, I. and Czechowski, A.: Interstellar dust in the model heliosphere: effects of  time-dependent heliospheric current sheet, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2860, https://doi.org/10.5194/egusphere-egu23-2860, 2023.

The solar magnetic fields emerging from the photosphere are comprised of a combination of “closed” and “open” fields. The closed magnetic field lines are defined as those having both ends rooted in the solar surface and not extending beyond the critical point, while the “open” field lines are those having one end that extends out into interplanetary space with the other end rooted at the Sun’s surface. Of course, there are no truly “open” magnetic field lines, and those that are dragged out into interplanetary space by the solar wind eventually close in the far reaches of the outer heliosphere. Since the early 2000’s, the amount of total unsigned open magnetic flux estimated by coronal models have been in significant disagreement with in situ spacecraft observations, especially during solar maximum, with factors of two or more differences not uncommon. Estimates of total open unsigned magnetic flux using coronal hole observations (e.g., using EUV or He 10830) are in general agreement with the coronal model results and thus are in similar disagreements with in situ observations. Several possible sources producing these discrepancies have been postulated over the years such as problems with the photospheric magnetic field measurements, underestimates of the polar field strengths, coronal mass ejection (CME) magnetic fields that are still closed but counted as open, the time-dependent nature of the magnetic field (i.e., the opening and closing of magnetic fields), and the manner in which in situ observations are used to estimate total open unsigned magnetic flux. This paper provides a brief review of the problem and some of the proposed explanations to account for the discrepancies. It concludes with compelling new evidence that appears to largely resolve the problem.

How to cite: Arge, C., Leisner, A., Wallace, S., and Henney, C.: On the Open Solar Magentic Flux Problem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3015, https://doi.org/10.5194/egusphere-egu23-3015, 2023.

The Chinese Hα Solar Explorer (CHASE) was successfully launched on 14 October 2021 as the first solar space mission of China National Space Administration (CNSA). The scientific payload of the CHASE satellite is the Hα Imaging Spectrograph (HIS). The CHASE/HIS acquires seeing-free spectroscopic observations of the whole solar disk at three spectral lines of Si I (6560.6 Å), Hα (6562.8 Å) and Fe I (6569.2 Å) which are formed at different heights of the photosphere and chromosphere. A full-Sun scanning takes only 46 seconds, with a spectral sampling of 0.024 Å and a spatial resolution of 1.2 arcsec. Since its launch and in-orbit calibrations, the performance of the CHASE mission is excellent and meets the pre-launch expectations. The FITS formatted science data are now available to the community through the Solar Science Data Center of Nanjing University (SSDC-NJU, https://ssdc.nju.edu.cn). Here we introduce the CHASE science data and the calibration procedures. The first series of scientific studies of the CHASE mission are also presented.

How to cite: Li, C., Fang, C., Ding, M., Chen, P., and Li, Z.: First results of the Chinese Ha Solar Explorer - CHASE mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3035, https://doi.org/10.5194/egusphere-egu23-3035, 2023.

Observations of Earth’s bow shock and magnetosheath have shown that magnetic reconnection occurs within these regions at thin current sheets, typically arising from turbulence and plasma instabilities in the shock transition layer. Broad observational surveys of these regions have shown that, somewhat surprisingly, the prevalence of reconnecting current structures may not be strongly dependent on the shock Mach number or the angle between the upstream magnetic field and shock normal (θ_Bn), despite quasi-parallel shocks typically exhibiting more disordered and non-stationary structure. To investigate how shock reconnection manifests across different parameters, we perform a series of two- and three-dimensional hybrid (fluid electron, kinetic ion) particle-in-cell simulations across a broad range of Mach numbers and orientations. These simulations isolate ion-scale mechanisms for reconnection in the shock, principally those driven by ion-ion beam instabilities in the foot and foreshock. For 2D simulations, we show that reconnection via these ion-driven mechanisms is strongly constrained to quasi-parallel shocks. However, downstream of quasi-parallel shocks, we find that the decay rate of closed-field regions, and hence thin current sheets, is not strongly dependent on upstream shock parameters. We also explore the differences that arise in shock structure, the generation of reconnecting current structures, and their decay rates for three-dimensional simulations.

How to cite: Gingell, I. L., Schwartz, S. J., Kucharek, H., Farrugia, C. J., Fryer, L. J., Plank, J., and Trattner, K. J.: Generation and Decay of Reconnecting Current Structures Downstream of the Bow Shock: 3D Hybrid Simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3166, https://doi.org/10.5194/egusphere-egu23-3166, 2023.

Connectivity between our star and our planet is a huge but necessary challenge. Indeed, remote-sensing instruments allow us to observe with great details the surface of the Sun, while in-situ measurements let us see the consequences at Earth. However, it it not always easy to understand the link between the two, thus preventing us from understanding the propagation of physical effects. One way to chase this connection is to use the magnetic field: although not visible, open magnetic field bathes the entire heliosphere, and has a major influence on plasma and particle events such as CMEs or flares. We can typically use numerical simulations to estimate the magnetic field lines pattern, and thus help connecting remote-sensing with in-situ observations.

In this study, we will present our computation of the magnetic connectivity through the heliosphere by coupling the MHD codes COCONUT for the solar corona and EUHFORIA for the inner heliosphere. MHD codes are usually too slow to compute connectivity on a near-real time cadence, but this chain of model can be optimised to run in less than 6 hours, which allows refined tracking within a single day. We will explain how the coupling between the code operates, as it effects the tracing of the magnetic field lines. We will also explain how to provide uncertainties with this method. We will first show the validation of our method by comparison with PFSS and wind ballistic mapping, for both polar and equatorial open coronal holes, on several test cases that were already used in previous studies. This will allow us to discuss the impact of the magnetic modelling on the connectivity estimation. Finally, we will also discuss the impact of the input magnetic map by comparing 20 different runs for the same Carrington rotation at minimum of activity, based on various maps from different providers.

How to cite: Perri, B., Kennis, S., Brchnelova, M., Baratashvili, T., Kuzma, B., Zhang, F., Lani, A., and Poedts, S.: Magnetic connectivity from the Sun to the Earth: Impact of the magnetic modelling and input magnetic map, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3536, https://doi.org/10.5194/egusphere-egu23-3536, 2023.

Models of the Solar Corona, ranging from potential field source surface (PFSS) to magnetohydrodynamic (MHD), typically provide a steady-state representation for a given time period, based on a single photospheric magnetic map.  However, the Sun's magnetic flux is in truth constantly evolving, and these changes in the flux affect the structure and dynamics of the corona and heliosphere.  The dynamics may be crucial to understanding solar wind properties.  A key question in the "Open Flux Problem" is whether the nature of open magnetic flux is adequately captured by steady-state PFSS and MHD models.  We describe an approach to evolutionary models of the corona and solar wind, using time-dependent boundary conditions.  We use the Lockheed Surface Flux Transport (SFT) model to evolve the surface magnetic fields, which in turn drive the coronal evolution.  The simulations are performed with the MAS thermodynamic Wave-Turbulence Driven (WTD) model for a month of simulated time.  We use the simulated observables derived from the simulation to explore the evolution of coronal structure (e.g., coronal hole boundaries).  We investigate the open magnetic flux in the model and contrast the results with MHD solutions using static magnetic flux boundaries at selected times.

How to cite: Linker, J. A., Mason, E., Lionello, R., Downs, C., Caplan, R., Titov, V., Riley, P., and DeRosa, M.: Open Magnetic Flux in the Time-Evolving Corona, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3939, https://doi.org/10.5194/egusphere-egu23-3939, 2023.

The complex dynamics of solar activity appear to be controlled by a number of individual oscillations from the monthly to the millennial scales, the most well-known of which is the 11-year Schwabe sunspot cycle. These oscillations are important also because many of them characterize the oscillations found in the climate of the Earth and could be used for climate change forecast purposes. However, the physical cause of the solar oscillations is still debated. Commenting on the origin of the 11-year sunspot cycle, Johann Rudolf Wolf (1859, MNRAS 19, 85–86) conjectured that “the variations of spot frequency depend on the influences of Venus, Earth, Jupiter, and Saturn.” There are only two options: either the solar activity changes are solely controlled by internal solar dynamo mechanisms or the solar dynamo itself is partially synchronized by external harmonic planetary forcings. The former hypothesis is today shared by the majority of solar scientists; the latter has been recently advocated by an increasing minority of solar scientists, and the debate is still going on. Here we overview the numerous pieces of evidence supporting a planetary theory of solar activity variability by demonstrating that the many planetary harmonics and the orbital invariant inequalities that characterize the planetary motions of the solar system from the monthly to the millennial time scales are not randomly distributed but clearly tend to cluster around some specific values that also match those of the main solar activity cycles. We also show that planetary models have even been able to predict the time phase of the solar oscillations including the Schwabe 11-year sunspot cycle. Although planetary tidal forces are weak, we review a number of mechanisms that could explain how the solar structure and the solar dynamo could get tuned to the planetary motions. In particular, we discuss how the effects of the weak tidal forces could be significantly amplified in the solar core by an induced increase in the H-burning. Mechanisms modulating the electromagnetic and gravitational large-scale structure of the planetary system are also discussed.

Main Reference:

Scafetta N and Bianchini A (2022) The Planetary Theory of Solar Activity Variability: A Review. Front. Astron. Space Sci. 9:937930. doi: 10.3389/fspas.2022.937930

Scafetta, N. (2020). Solar Oscillations and the Orbital Invariant Inequalities of the Solar System. Sol. Phys. 295, 33. doi:10.1007/s11207-020-01599-y

How to cite: Bianchini, A. and Scafetta, N.: An overview of the planetary theory of solar activity variability and its importance for understanding climate oscillations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4472, https://doi.org/10.5194/egusphere-egu23-4472, 2023.

The emergence of magnetic flux in the Sun can lead to the formation of active regions with highly complex magnetic fields, evident by δ-spots, filaments, and sigmoids. These regions are often the sources of major flares and coronal mass ejections (CMEs) and monitoring their evolution is crucial for a deeper understanding of these phenomena as well as space weather applications. To this end, high-quality observations of the photospheric magnetic field are routinely used to derive parameters and physical magnitudes, and quantify the magnetic complexity of active regions. Thus, we know that eruptive active regions are associated with highly non-potential magnetic field configurations, with strong electric currents and huge amounts of free magnetic energy and helicity. This talk reviews recent efforts to parameterize this non-potentiality of active regions and discusses ongoing and future work on developing new and improved parameters suitable for flare and CME prediction. It further focuses on the evolution of net electric currents in active regions, from their emergence to eruption. The significance of net electric currents on flare and CME prediction and new ways to utilize them in order to produce improved eruptivity parameters and understand solar eruptions will be discussed.

How to cite: Kontogiannis, I.: Parameterizing the evolution of active regions from emergence to eruption. Recent results and future work., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5436, https://doi.org/10.5194/egusphere-egu23-5436, 2023.

Imaging space plasmas via Energetic Neutral Atoms (ENA) is a widely used technique to study space plasma population ranging from the Earth’s magnetosphere all the way to the interstellar medium. Laboratory calibration against a known ENA beam source is a key element in the development and testing of spaceborne ENA imaging instruments. For ENA instruments operating at energies below about 1 keV, an ion beam source cannot be used for the instrument calibration, as ion trajectories are distorted through electromagnetic fields inside the ENA instrument whereas neutrals are not. The MEFISTO laboratory test facility at the University of Bern is well suited to carry out such ENA instrument calibrations: It provides neutral atom beams of any species from H to heavy elements at the relevant low-energy range from 3 keV down to 10 eV. MEFISTO is equipped with a large vacuum test chamber and an electron-cyclotron resonance ion source (ECRIS) for the production of a primary ion beam. Ion beam neutralization is performed with a dedicated neutralization stage via grazing scattering surface neutralization. This neutralization method introduces some uncertainty to the neutral beam energy and comes with species and energy dependent throughput.

Therefore, neutral beam calibrations have been conducted against a novel Absolute Beam Monitor (ABM), which serves as a primary calibration standard in the low-energy ENA range. Calibrated neutral beam fluxes and energies have been obtained for species of interest to interstellar, heliosphere and planetary science, including H, D, He, O, Ne neutral beams. The recently upgraded 5-axis movable hexapod table in the test chamber allows for precise motion and rotation of instrument under test relative to ENA calibration beam. These measures allow us to carry out thorough ENA instrument calibrations against a well-characterized low-energy neutral atoms beam source.

How to cite: Gasser, J., Galli, A., and Wurz, P.: Laboratory calibration of low-energy ENA instruments for space science, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5509, https://doi.org/10.5194/egusphere-egu23-5509, 2023.

The Interstellar Boundary Explorer (IBEX) is a NASA satellite in Earth’s orbit, observing both interstellar neutral atoms entering the heliosphere and energetic neutral atoms (ENAs) from the interstellar boundaries from roughly 10 eV to 6 keV. IBEX consists of two ENA imagers: IBEX-Lo covers the low energy range from 10 eV to 2 keV, IBEX-Hi covers ENA energies between 500 eV and 6 keV (corresponding roughly to solar wind energy).

ENA imaging is an indispensable tool in space physics. ENAs carry information on the plasma region where they were created that can be deciphered by analysis of the species, intensity, spatial distribution, and energy spectrum. The ENA intensity measured by a remote observer, such as IBEX, is a line of sight integral over potentially many different ion populations and local neutral atom densities. Thus, to derive properties of the heliosphere and of its plasma populations from such ENA measurements, they must be compared with the predictions of heliosphere models.

The majority of ENA model comparisons with IBEX observations so far were restricted to IBEX-Hi data. In this study, we present the first comparison of IBEX-Lo data with heliosphere models over one full solar cycle (using the tabulated energy spectra in Galli et al. 2022, http://dx.doi.org/10.3847/1538-4365/ac69c9). We use heliosphere models developed at the Moscow University and Boston University in this study. The comparison concentrates on the energy spectra of heliospheric ENAs originating from regions in the sky (such as Voyager 1, Voyager 2, South Pole, North Pole, and heliosphere downwind direction) that are cardinal directions for the comparison of the ENA data and the global heliosphere models.

This study is a part of the Research Team “Global Structure of the Heliosphere” within the SHIELD NASA DRIVE Science Center.

How to cite: Galli, A., Baliukin, I. I., Kornbleuth, M., Fuselier, S. A., Sokół, J. M., and Opher, M.: Comparison of heliosphere models with IBEX-Lo observations of Energetic Neutral Atoms at 50 eV - 2 keV energy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5688, https://doi.org/10.5194/egusphere-egu23-5688, 2023.

The mechanisms that produce solar energetic particles (SEPs) are still highly debated but coronal shock waves have been proposed as efficient particle accelerators that may be implicated in the production of SEPs.
An analysis of 32 Coronal Mass Ejections (CMEs) that produced strong pressure waves in the solar corona during their eruption has been done. For each event Kouloumvakos et al. (2019) exploited remote-sensing observations from multiple vantage points to reconstruct their 3-D ellipsoidal shapes. This catalogue of shock waves provides important statistical information on their kinematic evolution that we report in Jarry et al. (2023) together with their relation to X-ray flaring activitiy.
Different SEPs exhibit significant spectral and compositional variability. We looked for links between the composition of SEPs including abundance ratios (such as Fe/O) and shock parameters (Mach number, shock geometry, ..) that typically evolves rapidly along the magnetic field lines connected to the spacecraft recording SEPs.
This work was funded by the H2020 SERPENTINE project.

How to cite: Jarry, M., Rouillard, A., Plotnikov, I., Kouloumvakos, A., and Warmuth, A.: Relations between coronal shock waves properties and acceleration of solar energetic particles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6946, https://doi.org/10.5194/egusphere-egu23-6946, 2023.

Ion mass-per-charge and shock geometry determine both shock injection and the number of times a charged particle is reflected across a shock. As such, they govern charged particle acceleration and heating at shock. Solar Obiter’s Heavy Ion Sensor (HIS) observed a quasi-parallel CME-driven shock on March 11, 2022. HIS has sufficient time, mass, and charge resolution that it measured individual distributions of iron 8+ through 12+ on the variable timescale of 2 to 5 minutes. Using these 1D velocity distribution functions (VDFs), we report that the thermal portion of the Fe distribution heats across the shock, that this heating increases with Q/M, and the heating increases with distance downstream from the shock.

How to cite: Alterman, B. L., Livi, S., Owen, C., Louarn, P., Bruno, R., D'Amicis, R., Raines, J., Lepri, S., Spitzer, S., Dewey, R. M., Bert, C. M., Kistler, L., Galvin, A., Rivera, Y., Horbury, T., Trotta, D., Hietala, H., Fauchon-Jones, E., Gershkovich, I., and Verscharen, D. and the SWA and MAG Teams: Iron Heating Across a Shock Observed by Solar Orbiter's Heavy Ion Sensor, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7823, https://doi.org/10.5194/egusphere-egu23-7823, 2023.

Collisionless magnetohydrodynamic shocks are ubiquitous in solar wind and in other space plasmas. They serve as natural sites where charged particles can be accelerated to supra-thermal energies via various Fermi acceleration mechanisms. Upstream and downstream fluctuations play a key role in these processes because they can act as scatter centers. Furthermore, the downstream turbulent plasma of strong shocks driven by coronal mass ejections can enhance the coupling of this plasma with the Earth’s magnetosphere. Understanding of how the fluctuations are transmitted across the shocks can provide an invaluable insight into many shock related studies.

In this paper, we investigate the interaction of fast forward (FF) shocks with magnetic island/flux rope mode fluctuations. We employ a recently developed framework of the Zank et al. (2021) transmission model. We analyze 378 FF shocks observed by the Wind spacecraft with varying upstream conditions and Mach numbers. We estimate upstream and downstream power spectra within one-hour intervals adjacent to the shock front and we calculate theoretically predicted downstream power spectrum. We analyze closely the difference between the observed and theoretically predicted spectra. On average, the model predicts the spectra with very good accuracy. We argue that large statistical spread of this difference is given mainly by the statistical uncertainties in the shock compression ratio, upstream power spectrum and by the turbulent evolution of fluctuations in the downstream region. Finally, our findings also suggest that Zank et al. (2021) model may estimate the downstream levels of fluctuations accurately even for a wider range of shocks than it was originally meant for.

How to cite: Pitna, A., Zank, G., Nakanotani, M., Zhao, L., Adhikari, L., Šafránková, J., and Němeček, Z.: On the Transmission of Turbulence Across Interplanetary Shocks: Observations and Theory, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8250, https://doi.org/10.5194/egusphere-egu23-8250, 2023.

Interplanetary (IP) shocks are important sites of particle acceleration in the Heliosphere and can be observed in-situ utilizing spacecraft measurements. Such observations are crucial to address important aspects of energy conversion for a variety of astrophysical systems.

Under this point of view, Solar Orbiter provides observations of interplanetary shocks at different locations in the inner heliosphere with unprecedented time and energy resolution in the suprathermal (usually above 50 keV) energy range. We present a comprehensive identification of such shocks, highlighting their typical parameters.

We then study a strong shock showing novel dispersive signals in the suprathermal particle fluxes observed by the Solar Orbiter SupraThermal Electron and Proton sensor. These are probably due to irregular injection of particles to suprathermal energies along the shock front, as inferred using the Solar Orbiter in-situ observations and self-consistent, kinetic modelling of the shock transition.

How to cite: Trotta, D., Horbury, T., Hietala, H., Dresing, N., Vainio, R., Kilpua, E., Dimmock, A., Blanco-Cano, X., Lario, D., Koval, A., Wimmer-Schweingruber, R., Berger, L., and Yang, L.: Observations of energetic particles at interplanetary shocks with Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8760, https://doi.org/10.5194/egusphere-egu23-8760, 2023.

Synoptic magnetic field data usually serves as the boundary condition for simulations of the global magnetic field; however, it has been shown that these data suffer from an “aging effects” as the longitudinal 360° information can only be obtained over the course of one solar rotation. To avoid this, we use advanced magnetograms produced by feeding near-side HMI/SDO magnetograms and far-side helioseismic active regions into a modified surface flux transport model to improve the modeling of the far-side magnetic configuration. This allows for a more accurate description of the state of the global magnetic field and thus for an improved forecasting of solar wind parameters. We use potential field source surface (PFSS) and WSA modeling as well as the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) to derive the coronal magnetic field configuration and the heliospheric solar wind structure as well as discuss the changes caused by the implementation of far-side active regions into magnetic field maps. Modeled solar wind results are found to be in good agreement with far-side in-situ measurements taken by various instruments. We can show the importance of considering not only the solar near-side but also the far-side to accurately model the heliosphere in which solar transients are propagated.

How to cite: Heinemann, S. G., Yang, D., Pomoell, J., Arge, C. N., Jones, S. I., and Gizon, L.: FARM: Combined surface flux transport and helioseismic Far-side Active Region Model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8789, https://doi.org/10.5194/egusphere-egu23-8789, 2023.

Prediction of sunspots has been an everlasting interest in the space science community since the discovery of the sunspot cycle. The sunspot number is an indirect indicator of many different solar phenomena, e.g., total and spectral solar radiation, coronal mass ejections, solar flares and magnetic active regions. Its cyclic variation can even be used as a pacemaker to time different aspects of solar activity, solar wind and resulting geomagnetic variations. Therefore, there is considerable practical interest in predicting the evolution of future sunspot cycle(s). This is especially true in today’s technological society where space hazards pose a significant threat, e.g., to satellites, communications and electric grids on ground have been recognized. Another interest to predicting sunspots arises from the relatively recently recognized influences of variable solar radiation and solar wind activity on Earth’s climate system.

There are a variety of methods developed for predicting sunspots ranging from statistical methods to intensive physical simulations. Some of the most successful, yet relatively simple, methods are based on finding precursors that serve as indicators for the strength of the coming solar cycle. These methods are often based on statistics of all past solar cycles. However, most of these methods do not typically take into account the 22-year Hale cycle of solar magnetism, which is well known in different solar and geomagnetic phenomena.

Here we study the prediction of even and odd numbered sunspot cycles separately, thereby taking into account the Hale cyclicity of solar magnetism. We first show that the temporal evolution and shape of all sunspot cycles are extremely well described by a simple parameterized mathematical expression. We find that the parameters describing even sunspot cycles can be predicted quite accurately using the sunspot number 41 months prior to sunspot minimum as a precursor. The parameters of the odd cycles can be best predicted with geomagnetic maximum geomagnetic aa index close to fall equinox within a 3-year window preceding the sunspot minimum. Cross-validated hindcasts indicate that our method has a very good prediction accuracy. For the coming sunspot cycle 25 we predict an amplitude of 171 +/- 23 and the end of the cycle in September 2029 +/- 1.9 years. We are also able to make a rough prediction for cycle 26 based on the predicted cycle 25. While the uncertainty for the cycle amplitude is large we estimate that the cycle 26 will likely be stronger than cycle 25. These results suggest an increasing trend in solar activity for the next two decades.

How to cite: Asikainen, T. and Mantere, J.: Prediction of even and odd sunspot cycles: implications for cycles 25 and 26, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8849, https://doi.org/10.5194/egusphere-egu23-8849, 2023.

Interplanetary (IP) shocks can be driven in the solar wind by fast coronal mass ejections and by the interaction of fast solar wind with slow streams of plasma. These shocks can be preceded by extended waves and suprathermal ion foreshocks. Shocks characteristics as well as the level of wave activity near them change as they propagate through the heliosphere and this can impact particle acceleration, and modify the ambient solar wind. In this work we study IP shock evolution and the wave modes upstream of them using a multispacecraft approach with data of Solar Orbiter, STEREO, Parker Solar Probe and Wind. We find that upstream regions can be permeated by whistler waves (f ~ 1 Hz) and/or ultra low frequency (ULF) right-handed waves (f~10^-2–10^-1 Hz). While whistlers appear to be generated at the shock, the origin of ULF waves is most probably associated with local kinetic ion instabilities. In contrast with planetary bow shocks, most IP shocks have a small Mach number (<4) and most of the upstream waves studied here are mainly transverse and steepening rarely occurs.

How to cite: Blanco-Cano, X., Trotta, D., Hietala, H., Kajdic, P., Rojas-Castillo, D., Dimmock, A., Horbury, T., Vainio, R., and Jian, L.: Waves upstream of interplanetary shocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9785, https://doi.org/10.5194/egusphere-egu23-9785, 2023.

Collisionless shocks exist across diverse plasma environments. Examples are supernova remnants, comets, near planets, and interplanetary (IP) shocks in the solar wind. As the shock Mach number increases, so does the complexity of the ion distribution functions at the shock front due to features such as whistler precursors, ion reflection, shock ripples, and nonstationarity. 

Experimental studies of ion dynamics at supercritical high Mach (>5) number shocks are typically conducted using planetary bow shock crossings since the Mach number of these shocks are higher while the shock speeds with respect to the observing spacecraft are lower. As a result, it is easier to resolve complex features in the ion velocity distribution function. For these reasons, studies concentrating on ion reflection at IP shocks are rare. However, comparisons with IP shocks are interesting since they have a much larger curvature radius and can be accompanied by more energetic particles.

In this work, we analyze a quasi-perpendicular shock observed by Solar Orbiter (SolO) on 30 October 2021 with a Mach number of around 7; this is much higher than the typical values of SolO IP shocks, which are between 1-3. For this event, we observed clear signatures in the upstream ion distribution function of reflected ions with energies extending to around 15 keV, which is lower than reported by other studies. The shock also demonstrates a non-planar feature, which may indicate shock rippling. In addition, whistler precursors are also found immediately upstream locally within the shock foot. We present these experimental results and a comparison with test-particle analysis and numerical modeling results.

How to cite: Dimmock, A., Gedalin, M., Trotta, D., Lalti, A., Graham, D., Khotyaintsev, Y., Vainio, R., Blanco-Cano, X., Kajdič, P., and Owen, C.: Ion reflection observed at high Mach number interplanetary shocks: Solar Orbiter observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11192, https://doi.org/10.5194/egusphere-egu23-11192, 2023.

Turbulence in plasmas involves a complex cross-scale coupling of fields and distortions of particle velocity distributions, with the generation of non-thermal features. How the energy contained in the large-scale fluctuations cascades all the way down to the kinetic scales, and how such turbulence interacts with particles, remains one of the major unsolved problems in plasma physics. Moreover, solar wind turbulence is not homogeneous but is highly space-localized and the degree of non-homogeneity increases as the spatial/time scales decrease (intermittency). Such an intermittent nature has also been found to evolve with distance from the Sun, possible due to the emergence of strong non-homogeneities over a broad range of scales.

Here, by means of new measurements by both Solar Orbiter and Parker Solar Probe, the radial evolution of a homogeneous recurrent fast wind, coming from the same source on the Sun (namely a coronal hole), has been studied from global properties and large-scale features to kinetic structures as it expands in the inner heliosphere from 0.1 out to 1 AU [Perrone et al., 2022]. In particular, the nature of the turbulent magnetic fluctuations around ion scales during the expansion of the wind, has been investigated and the observed coherent events both close to the Sun and to the Earth are statistically studied. The ion scales appear to be characterized by the presence of non-compressive coherent structures, such as current sheets, vortex-like structures, and wave packets identified as ion cyclotron modes, responsible for solar wind intermittency and strongly related to the energy dissipation. Particle energization, temperature anisotropy, and strong deviation from Maxwellian, have been observed in and near coherent structures, both in in-situ data and numerical simulations. Understanding the physical mechanisms that produce coherent structures and how they contribute to dissipation in collisionless plasma will provide key insights into the general problem of solar wind heating.

Perrone, D., et al. (2022) Astronomy & Astrophysics (Special Issue: Solar Orbiter First Results – Nominal Mission Phase) 668, A189

How to cite: Perrone, D.: Turbulence evolution of coronal hole solar wind in the inner heliosphere: Solar Orbiter and Parker Solar Probe combined observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11253, https://doi.org/10.5194/egusphere-egu23-11253, 2023.

In situ and remote observations of the outer regions of the heliosphere and in the local interstellar medium (LISM) by Voyager, New Horizons, and IBEX continue to present new challenging questions, reflecting the complex processes of the solar wind (SW) - local interstellar medium (LISM) interaction. We present a new version of our recent 3-D MHD-plasma/kinetic-neutrals model of the SW-LISM interaction, which self-consistently includes neutral hydrogen and helium atoms. The new model treats electrons as a separate fluid assumed to co-move with the plasma mixture. In addition, it includes the effect of Coulomb collisions between electrons, He+ ions, and protons. The properties of electrons in the distant SW and in the very local interstellar medium (VLISM) are mostly unknown due to the lack of in situ observations. In this study we discuss the implications of using different models for the electron pressure. A common assumption (model 0) in single-ion global models is to assume that electrons have the pressure of the ion mixture. In this case electrons become hot in the distant SW where plasma is energetically dominated by pickup ions. In the proposed new model, electrons in the SW are colder, which leads to a better agreement with New Horizons observations in the supersonic SW. In the VLISM, however, ions and electrons may be almost in thermal equilibrium due to Coulomb collisions. As far as the plasma mixture properties are concerned, the major differences between the models are in the inner heliosheath, where colder electrons result in hotter protons and induce cooling of the plasma mixture due to the increase in the charge exchange frequency. This makes the heliosheath thinner by ~5 AU along the upstream direction and up to 60 AU in the downwind region. The filtration of interstellar H and He atoms is also discussed. At 1 AU, in the model with separate electrons the H density increases by ~2%. However, the fraction of pristine H atoms decreases by ~12%, while that of atoms born in the IHS increases up to ~35%. While the density of He atoms in the SW remains essentially unchanged, the contribution from the warm breeze increases by ~3%.

How to cite: Fraternale, F., Pogorelov, N. V., and Bera, R. K.: The role of electrons and helium atoms in global modeling of the heliosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11714, https://doi.org/10.5194/egusphere-egu23-11714, 2023.

The solar wind is an uninterrupted flow of highly ionised plasma that streams from compact sources at or near the Sun, accelerates across the low solar corona, and expands into the whole interplanetary space. The physical properties of any wind streams thus reflect the characteristics of their source regions and those of the extended zones of the corona they cross, and are affected by the time-varying strength and geometry of the global background magnetic field.  The rotational state of the solar corona also plays a fundamental role in a wide range of solar wind phenomena, but is much less well-known than that of the photosphere. In addition, surface dynamics and magnetic field evolution drive perturbations to the corona and wind that can either be transient or long-lasting.
We investigate the geometry and spatial distribution of solar wind sources by means of an extended time series of data-driven 3D simulations that cover nearly 2 activity cycles. We furthermore examine the corresponding solar wind acceleration profiles (radial trends) as a function of source latitude and time, and highlight consequences for the interpretation of Parker Solar Probe (PSP) and Solar Orbiter (SolO) in-situ measurements (especially as the latter moves away from the ecliptic plane). We also highlight impacts on the rotation profile of the solar corona and on the occurrence of regions of enhanced poloidal and toroidal flow shear that can drive plasma instabilities. Finally, we point out directions to assess the effects of surface transient phenomena driven by flux emergence on the properties of the solar wind.

How to cite: Pinto, R., Rouillard, A., and Finley, A.: Steady and transient solar wind sources, acceleration profiles and rotation across the solar activity cycle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12000, https://doi.org/10.5194/egusphere-egu23-12000, 2023.

Localized dynamic pressure enhancements - jets - are regularly observed downstream of the Earth’s bow shock. They drive enhanced particle acceleration, larger amplitude magnetic field variations and reconnecting current sheets. Various shock simulations have also exhibited jets, suggesting that they are not unique to Earth.

In this study, we search for similar dynamic pressure pulses downstream of interplanetary shocks observed by the Wind spacecraft. We discuss how the jet selection criteria are adapted for such conditions. The interplanetary shocks where we have found jet candidates feature foreshock activity, a favourable condition for jet formation according to bow shock studies. We examine the properties of the candidate jets and compare them to those reported for magnetosheath jets. Widening the range of environments where downstream jets are observed can shed light on their dynamics and formation mechanisms.

How to cite: Hietala, H., Trotta, D., Wilson III, L., Fedeli, A., and Vuorinen, L.: Candidates for downstream jets at interplanetary shocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12727, https://doi.org/10.5194/egusphere-egu23-12727, 2023.

Coronal holes are characterized by open magnetic field lines morphology. The strongest solar wind originates exactly from the area of solar coronal holes. From the other hand the solar oscillation is present at every point of the solar surface. Currently the mechanism which is responsible for formation of open coronal regions is still unidentified. We present a novel study of waves propagation and frequency distribution in coronal holes, which can bring a new insights in its origin. We investigate the discrepancies in the in waves propagation inside the coronal hole are and in its surrounding, using multi-channel intensity observations data from Atmospheric Imaging Assembly (AIA) and Dopplergrams from Helioseismic and Magnetic Imager (HMI) on board Solar Dynamics Observatory (SDO) at the level of photosphere, chromosphere and corona. We study power distribution of p-modes (5-minute oscillation) and wave frequencies above the acoustic cut-off frequency ѵ=5.3 mHz, for very fast waves, in the various levels of solar atmosphere, through helioseismic approach of wavelet 2D-spatial maps of the power spectral density estimated for the coronal hole area.

How to cite: Wisniewska, A.: Frequency Distribution of Solar Oscillation Inside The Coronal Hole, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13848, https://doi.org/10.5194/egusphere-egu23-13848, 2023.

Since the 1970s it has been empirically known that the area of solar coronal holes a ects the properties of high-speed solar wind
streams (HSSs) at Earth. We derive a simple analytical model for the propagation of HSSs from the Sun to Earth and thereby show
how the area of coronal holes and the size of their boundary regions a ect the HSS velocity, temperature, and density near Earth.
We assume that velocity, temperature, and density profiles form across the HSS cross section close to the Sun and that these spatial
profiles translate into corresponding temporal profiles in a given radial direction due to the solar rotation. These temporal distributions
drive the stream interface to the preceding slow solar wind plasma and disperse with distance from the Sun. The HSS properties at
1AU are then given by all HSS plasma parcels launched from the Sun that did not run into the stream interface at Earth distance.
We show that the velocity plateau region of HSSs as seen at 1AU, if apparent, originates from the center region of the HSS close
to the Sun, whereas the velocity tail at 1AU originates from the trailing boundary region. Small HSSs can be described to entirely
consist of boundary region plasma, which intrinsically results in smaller peak velocities. The peak velocity of HSSs at Earth further
depends on the longitudinal width of the HSS close to the Sun. The shorter the longitudinal width of an HSS close to the Sun, the
more of its “fastest” HSS plasma parcels from the HSS core and trailing boundary region have impinged upon the stream interface
with the preceding slow solar wind, and the smaller is the peak velocity of the HSS at Earth. As the longitudinal width is statistically
correlated to the area of coronal holes, this also explains the well-known empirical relationship between coronal hole areas and HSS
peak velocities. Further, the temperature and density of HSS plasma parcels at Earth depend on their radial expansion from the Sun
to Earth. The radial expansion is determined by the velocity gradient across the HSS boundary region close to the Sun and gives the
velocity-temperature and density-temperature relationships at Earth their specific shape. When considering a large number of HSSs,
the assumed correlation between the HSS velocities and temperatures close to the Sun degrades only slightly up to 1AU, but the
correlation between the velocities and densities is strongly disrupted up to 1AU due to the radial expansion. Finally, we show how
the number of particles of the piled-up slow solar wind in the stream interaction region depends on the velocities and densities of the
HSS and preceding slow solar wind plasma.

How to cite: Hofmeister, S., Asvestari, E., Guo, J., Heidrich-Meisner, V., Heinemann, S., Magdalenic, J., Poedts, S., Samara, E., Temmer, M., Vennerstrom, S., Veronig, A., Vrsnak, B., and Wimmer-Schweingruber, R.: The effect of the morphology of coronal holes on the propagational evolution of high-speed solar wind streams in the inner heliosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14753, https://doi.org/10.5194/egusphere-egu23-14753, 2023.

Current sheets in the collisionless solar wind usually have kinetic spatial scales. In-situ measurements show that these current sheets are often approximately force-free, i.e. the directions of their current density and magnetic field are aligned, despite the fact that the plasma beta is found to be of the order of one. The measurements also often show systematic asymmetric spatial variations of the plasma density and temperature across the current sheets, whilst the plasma pressure is approximately uniform. Neukirch et al. (2020) found exact equilibrium models of force-free collisionless current sheets which allowed for asymmetric plasma density and temperature gradients. These models assumed that the form of the distribution function for electrons and ions is the same. If one assumes that the bulk velocity of the ion population vanishes, the force-free condition is only satisfied approximately. Also, quasi-neutrality requires the presence of a nonvanishing electric potential. We show that an approximate treatment implies that the asymmetries in the density and the temperature only differ by a scale factor from the asymmetries found for the exactly force-free case.

T. Neukirch, I. Vasko, A. Artemyev and O. Allanson, ApJ 891, 86 (2020).

How to cite: Neukirch, T., Vasko, I., Artemyev, A., and Allanson, O.: Kinetic models of asymmetric solar wind current sheets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15303, https://doi.org/10.5194/egusphere-egu23-15303, 2023.

MMS can resolve the fine structure of the shock ramp, which often shows holes in reduced ion-phase space distributions (integrated along the tangential plane of the shock). This is possible due to the high temporal resolutions of FPI/DIS. Such holes have been associated with ripples propagating along the shock surface but also can be related to the shock reformation. We statistically characterize the ion phase-space holes at the Earth’s bow shock using MMS observations. We establish a systematic procedure to find the shocks exhibiting the phase-space holes. We apply the procedure to ~500 shock crossings for which the burst data necessary to identify the holes is available. We identify phase-space holes for 66% of the crossings. We note that the actual occurrence is likely higher, as the holes are not resolved for fast shock crossings. We characterize the occurrence of the holes as a function of shock parameters such as Mach number and geometry. We find that the holes are widespread at the bow shock and are present for a wide range of shock geometries and Mach numbers (M_A) studied. Their occurrence has no dependence on the shock geometry and increases with the Mach number, M_A. The highest occurrence (70% probability) is for M_A above 5. These results are essential to understanding the non-stationary behavior of collisionless shocks.

How to cite: Khotyaintsev, Y., Lotekar, A., Johlander, A., Graham, D., and Lalti, A.: Statistical Study of Shock Rippling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15872, https://doi.org/10.5194/egusphere-egu23-15872, 2023.

Mathematical Morphology (MM) is an effective method to identify different types of features visible on the solar surface such as sunspots, facular regions, and pre-eruptive configurations of Coronal Mass Ejections (CMEs), which are important indicators of the Sun’s activity cycle.  On the one hand, we determine sunspots areas in Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) intensity images with this MM method, and we compare the obtained values with existing solar databases (e.g., the Debrecen Heliophysical Observatory catalogue or Mandal et al.'s catalogue [2020, A&A doi:10.1051/0004-6361/202037547]). The good agreement between the MM results and the existing catalogues validates the method, which we then apply to contour the different magnetic polarities in the SDO/Helioseismic and Magnetic Imager (HMI) magnetograms in order to identify so-called delta-sunspots. The next step is to investigate the correlation between solar flares and the length of these delta-sunspots contours. On the other hand, as another application, MM also helps us to extract flux rope structures from magnetic field models, using twist number maps obtained from a time-dependent magnetofrictional code. We can then investigate the evolution of the magnetic flux rope properties and the underlying triggers for the instability that ultimately leads to an eruption.

How to cite: Bourgeois, S., Wagner, A., Barata, T., Erdélyi, R., and Oliveira, O.: Mathematical Morphology applied to solar features detection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16533, https://doi.org/10.5194/egusphere-egu23-16533, 2023.

Impulsive solar energetic particle (SEP) events are distinguished from shock-accelerated gradual SEP events especially in terms of their abundance enriched in ³He and heavy ions. Historically, ³He-rich  have been known to be accompanied by type III radio bursts and energetic electrons. For more than 15 years in the past it has often been proclaimed that coronal jets are responsible for ³He-rich SEP events. We revisit the link of ³He-rich SEP events with coronal jets in a series of ³He-rich SEP events that was observed by Solar Orbiter in May 2021 at a radial distance of 0.95 AU. An isolated active region AR 12824 was likely the ultimate source of these SEP events.  The period of the enhanced flux of ³He was also a period of frequent type III bursts in the  decametric-hectometric range, confirming their close relationship. As in past studies, we try to find the solar activities possibly responsible for ³He-rich SEP events, using the type III bursts close to the particle injection times estimated from the velocity dispersion. But this exercise is not as straightforward as in many of the past studies since the region produced many more type III bursts and jet-like eruptions than the SEP injections.  We may generalize the solar activities for the ³He-rich SEP events in question as coronal jets, but their appearances do not necessarily conform to classic jets that consist of a footpoint and a spire. Conversely, such jets often did not accompany type III bursts. The areas that produced jet-like eruptions changed within the active region from the first to the second set of ³He-rich SEP events, which may be related to the extended coronal mass ejection that launched stealthily, involving both the leading and trailing polarity areas of AR 12824.

How to cite: Nitta, N., Bucik, R., Mason, G., Ho, G., Cohen, C., Gomez-Herrero, R., Wang, L., and Balmaceda, L.: Solar Activities Associated with 3He-rich Solar Energetic Particle Events Observed by Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16814, https://doi.org/10.5194/egusphere-egu23-16814, 2023.

As the coronal dynamics is dominated by magnetic forces, the reconstruction of the coronal magnetic field is of major importance when studying the solar corona. Since coronal field measurements are not routinely available, photospheric fields are extrapolated into the corona in order to obtain the 3D coronal magnetic field structure. A nonlinear force-free field approximation is justified because of the low plasma  $\beta$. Previous extrapolation codes excluded high and low latitudes, because of the well know grid convergence problems at the poles. To overcome these limitations, we developed a new code implemented on a Yin-Yang grid, which was tested and verified with the Low and Lou solution as reference. Here we apply our code to synoptic vector magnetograms obtained from SDO/HMI during solar activity maximum and minimum, respectively. We compare our magnetic field models with EUV-observations of the solar corona as a first validation step.

How to cite: Koumtzis, A., Wiegelmann, T., and Madjarska, M.: Computing the global coronal magnetic field during activity maximum and minimum with a newly developed nonlinear force-free Yin-Yang code, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17168, https://doi.org/10.5194/egusphere-egu23-17168, 2023.

The launch of new spacecraft such as Parker Solar Probe or Solar Orbiter allow us to measure in-situ at different radial distances the physical magnitudes of ICMEs. With that, we are able to quantify the evolution of ICMEs and their substructures at a specific radial distance in order to better understand the interaction processes that occur with the background solar wind.
Using multiple spacecraft covering the inner heliosphere, we extract plasma and magnetic field parameters from several ICMEs to relate the physical processes responsible for the formation of the different substructures. We present ICME case studies that prepare for a large statistical analysis.

How to cite: Larrodera, C. and Temmer, M.: Study of the evolution of interplanetary coronal mass ejections in the inner heliosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1386, https://doi.org/10.5194/egusphere-egu23-1386, 2023.

Magnetic switchbacks are rapid high amplitude reversals of the radial
magnetic field in the solar wind that do not involve a heliospheric
current sheet crossing. First seen sporadically in the seventies in
Mariner and Helios data, switchbacks were later observed by the
Ulysses spacecraft beyond 1 au and have been recently identified as a
typical component of solar wind fluctuations in the inner heliosphere
by the Parker Solar Probe spacecraft. We provide a simple yet
predictive theory for the formation of these magnetic reversals: the
switchbacks are produced by the shear of circularly polarized Alfven
waves by a transversely varying radial wave propagation velocity.  The
wave speed can be modulated by variations in bulk velocity, radial
magnetic field, density or any combination of these.  We provide an
analytic expression for the magnetic field variation as a function of
the wave velocity shear, establish the necessary and sufficient
conditions for the formation of switchbacks and show that the
mechanism works in a realistic solar wind scenario. The suggested
mechanism is in full agreement with Parker Solar Probe observations,
including the shape of the switchbacks, the correlations of the
components of the magnetic field, and the dependence of various
quantities on radial distance.  We show conclusively that this is the
fundamental process that creates switchbacks.

How to cite: Toth, G.: A Simple yet Correct Theory for the Formation of Magnetic Switchbacks Observed by Parker Solar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2914, https://doi.org/10.5194/egusphere-egu23-2914, 2023.

We report observations of <100 keV/nucleon suprathermal (ST) H, He, O, and Fe ions in association with three separate crossings of the heliospheric current sheet that occurred near perhelia during PSP encounters 7-11. In particular, we compare and contrast the ST ion time-intensity profiles, velocity dispersion, pitch-angle distributions, spectral forms, and maximum energies during the three HCS crossings. We find that these unique ST observations are remarkably different in each case, with those during E07 posing the most serious challenges for existing models of ST ion production in the inner heliosphere. In contrast, the ISOIS observations during 4 separate HCS crossings during E08-11 appear to be consistent with a scenario in which ST ions escape out of the reconnection exhausts into the separatrix layers after getting accelerated up to ~50-100 keV/nucleon by HCS-associated magnetic reconnection-driven processes. We discuss these new observations in terms of local versus remote acceleration sources as well as in terms of expectations of existing ST ion production and propagation, including reconnection-driven and diffusive acceleration in the inner heliosphere.

How to cite: Desai, M. and the Parker Solar Probe ISOIS, SWEAP, and FIELDS Science Teams: Suprathermal Ion Observations Associated with the Heliospheric Current Sheet Crossings by Parker Solar Probe During Encounters 7-11, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3494, https://doi.org/10.5194/egusphere-egu23-3494, 2023.

Magnetic switchbacks are short magnetic field reversals ubiquitously observed in the solar wind. The origin of switchbacks remains an important open science question, because of switchbacks’ possible role in the heating and acceleration of the solar wind. Here, we report observations of 501 robust switchbacks, using magnetic and plasma measurements from the first eight encounters by the Parker Solar Probe (PSP). More than 46% (6%) of switchbacks are rotational (tangential; TD) discontinuities (RD), defined as magnetic discontinuities with large (small) relative normal components of magnetic field and proton velocity. Magnetic reconnection in the solar atmosphere can be a source of the observed RD-type switchbacks. It is discovered that: 1) the RD-to-TD ratio exponentially decays with increasing heliocentric distance at rate 0.06 [R_S^-1], and 2) TD-type switchbacks contain 64% less magnetic energy than RD-type switchbacks, suggesting that RD-type switchbacks may relax into TD-type switchbacks. It is estimated that relaxing switchbacks generated via magnetic reconnection in the solar atmosphere can transfer an additional 16% of the total reconnected magnetic energy into heating and/or accelerating the solar corona, within 11.6 [R_S] of the reconnection site. The roles of turbulence and/or waves in dissipating this energy into heating and/or accelerating the solar corona plasma are the remaining open science questions.

How to cite: Akhavan-Tafti, M., Kasper, J., Huang, J., and Thomas, L.: Magnetic Switchbacks Heat the Solar Corona, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3671, https://doi.org/10.5194/egusphere-egu23-3671, 2023.

There are few possibilities to put the in-situ measurements of the coronal electron density such as obtained by the Parker Solar Probe (PSP) in the context of the 3D configuration of the corona and its structure. One of them consists in using MHD models relying on synoptic maps of the photospheric magnetic field, but their accuracy is subject to questions, especially in the case of complex coronae of the maximum type. The 2D inversion of white-light coronagraphic images requires the simplified assumption of spherical symmetry of the corona which basically washes out the longitudinal variations. We will present preliminary results of a new method which makes use of the 3D time-dependent tomographic reconstruction of the coronal electron density based on accurately corrected and calibrated LASCO-C2 images of the polarized brightness of the corona. It is performed over a sliding window of 14 days (half a Carrington rotation) centered at the times of the PSP perihelion with a time interval of 4 days. The resulting “cubes” of the 3D electron density Ne are visualized from six different vantage points and with movies. The orbit of PSP is projected on a synoptic map of Ne extracted from the cubes at a heliocentric distance of 5.5 Rs; the track extends from Perihelion-5 days to Perihelion+5 days. The electron density at the heliocentric distances of PSP is extrapolated radially from the values at 5.5 Rs using an inverse square law and compared with the in-situ measurements collected by PSP/FIELDS. We will present results from the first PSP encounters.

How to cite: Lamy, P. and Wojak, J.: Connecting Coronal 3D Electron Density from Tomographic Reconstruction to In-situ Measurements from Parker Solar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4352, https://doi.org/10.5194/egusphere-egu23-4352, 2023.

Coronal Mass Ejections (CMEs) are large-scale eruptions from the Sun that drive shocks and turbulent sheaths ahead of them. Parker Solar Probe, Solar Orbiter and BepiColombo have recently observed several shocks/sheaths closer to the Sun than the Earth’s orbit. These studies have revealed enhanced energetic proton fluxes from in-situ observations in interplanetary space also in the sheaths preceding slow CMEs. In this presentation we discuss the internal small-scales sheath structures (e.g., mini flux ropes) and embedded magnetic fluctuations as well as related energization mechanisms. The results suggest that the CME-driven sheaths can have an important role in the acceleration of energetic particles.

How to cite: Kilpua, E. and the Emilia Kilpua: Coronal Mass Ejection driven sheath regions and proton acceleration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4437, https://doi.org/10.5194/egusphere-egu23-4437, 2023.

Understanding the physical processes underlying solar radio bursts requires both high- and low-frequency observations, as well as imaging capabilities. In this study, we implement a fully automated approach to detect and characterize type III radio bursts, image their sources in the corona, and characterize the plasma environment where the bursts are triggered. We utilize data from the Low-Frequency Array (LOFAR) and the Parker Solar Probe (PSP) to investigate several type-III radio bursts that occurred on April 3, 2019. Through data pre-processing and combining the LOFAR and PSP dynamic spectra, we study the solar radio emissions between 2.6 kHz and 80 MHz. By extracting the frequency drift and speed of the accelerated electron beams, we gain insight into the physical processes driving these bursts. Additionally, by using LOFAR interferometric observations to image the sources of the radio emission at multiple frequencies, we are able to determine the locations and kinematics of the sources in the corona. We also use Potential Field Source Surface (PFSS) modeling and magnetohydrodynamic (MHD) simulation results to determine the magnetic field configuration and plasma parameters in the vicinity of the moving emission sources. These observations and analysis provide valuable constraints on the coronal conditions that trigger solar radio bursts.

How to cite: Nedal, M., Kozarev, K., Zhang, P., and Zucca, P.: Coronal Diagnostics of Solar Type-III Radio Bursts Using LOFAR and PSP Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4502, https://doi.org/10.5194/egusphere-egu23-4502, 2023.

Parker Solar Probe (PSP) and Solar Orbiter (SolO) observe the Sun from unprecedented close-in orbits out of the Sun-Earth line. In combination with EUV imagery from STEREO and SDO, these unique and high-resolution data from different vantage points will give us new insights into the early evolution of coronal mass ejections (CMEs) in the low corona and inner heliosphere. For a case study, we apply 3D CME reconstruction methods to relate different CME substructures as observed in white-light coronagraphs like WISPR aboard PSP, to EUV off-limb structures for an erupting event. We interpret the results in terms of projection and Thomson scattering effects.

How to cite: Cappello, G., Temmer, M., and Veronig, A.: Substructures of coronal mass ejections (CMEs) and their solar source region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5698, https://doi.org/10.5194/egusphere-egu23-5698, 2023.

Type III radio emissions are often observed by the Solar Orbiter spacecraft in the solar wind. They arise from a mode conversion of Langmuir waves generated by electron beams ejected from the Sun. In this study, we analyze sources of type III radio emissions that occurred after July 2020. We use data from the Radio and plasma waves (RPW), Energetic particle detector (EPD), Magnetometer (MAG), and Solar Wind Analyzer (SWA) instruments. We identify in-situ type III events and examine various parameters that may have influenced their generation mechanism. We use the maximum amplitude (MAMP) data product from the Time Domain Sampler (TDS) receiver of the RPW instrument for continuous tracking of Langmuir wave packets. For in-situ type III events throughout the Solar Orbiter mission, we study the wave polarization of the locally generated Langmuir waves measured in the Y-Z plane of the spacecraft reference frame. Using data from the EPD instrument, we obtain electron beam velocities for several in-situ events. We show that the electron beam velocity for those events is higher than predicted by previous studies.

How to cite: Formánek, T., Píša, D., Souček, J., Santolík, O., Vecchio, A., Maksimovic, M., Rodríguez-Pacheco, J., Horbury, T., and Owen, C. J.: Analysis of type III radio emissions observed by the Solar Orbiter spacecraft close to their source locations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7326, https://doi.org/10.5194/egusphere-egu23-7326, 2023.

How to cite: wang, X., Chapman, S., Dendy, R., and Hnat, B.: Wavelet determination of magnetohydrodynamic range power spectral exponents in solar wind turbulence seen by Parker Solar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7866, https://doi.org/10.5194/egusphere-egu23-7866, 2023.

Since its launch, the Parker Solar Probe (PSP) mission revealed the presence of numerous fascinating phenomena occurring closer to the Sun, such as the presence of ubiquitous switchbacks (SBs). The SBs are large magnetic field deflections of the local magnetic field relative to a background field. We investigated the statistical properties of the SBs during the first ten encounters between 13.3 and 70 Solar Radii using data from the SWEAP and FIELDS suites onboard PSP . We find that the occurrence rate of small deflections with respect to the Parker spiral decreases with radial distance (R). In contrast, the occurrence rate of the large deflections (SBs) increases with R, as does the occurrence rate of SB patches. We also find that the occurrence of SBs correlates with the bulk velocity of the solar wind, i.e., the higher the solar wind velocity, the higher the SB occurrence. For slow wind, the SB occurrence rate shows a constantly increasing trend between 13.3 and 70 solar radii. However, for fast wind, the occurrence rate saturates beyond 35 solar radii. Sub-Alfvenic regions encountered during encounters 8-10 have not shown significant SBs. This analysis of the PSP data hints that some of the SBs are decaying and some are being created in-situ.

How to cite: Jagarlamudi, V. K., Raouafi, N. E., Bourouaine, S., Mostafavi, P., and Larosa, A.: Occurrence and evolution of switchbacks between 13.3 to 70 solar radii: PSP Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8514, https://doi.org/10.5194/egusphere-egu23-8514, 2023.

Just after orbit 12 closest approach, on 2 June 2022 at a distance of 14 R_S, the Integrated Science Investigation of the Sun (ISʘIS) observed a ³He-rich solar energetic particle (SEP) event.  The event was associated with an active region just over the east limb (as viewed from Earth), which erupted with an occulted C1.2 class x-ray flare and a coronal mass ejection (CME) traveling ~350 km/s.  PSP observed a type III radio burst associated with the flare, followed by a type III storm.  After the initial dispersive SEP event, ISʘIS observed a second enhancement of energetic particles contained within the associated CME as it passed over the spacecraft.  Comparisons of these two populations provide information regarding the acceleration of particles at the Sun as well as trapping or acceleration within the CME structure as different components of an individual solar event.

How to cite: Cohen, C. and the ISOIS/FIELDS/SWEAP/WISPR study team: Observations by Parker Solar Probe of a 3He-rich Solar Energetic Particle Event at 14 RS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9578, https://doi.org/10.5194/egusphere-egu23-9578, 2023.

On 15 February 2022, an impressive filament eruption was observed off the solar eastern limb from three remote-sensing viewpoints, namely Earth, STEREO-A, and Solar Orbiter. Apart from representing the most-distant observed filament at extreme ultraviolet wavelengths—captured by Solar Orbiter's field of view extending to above 6 Rs—this event was also associated with the release of a fast (~2200 km/s) coronal mass ejection (CME) that was directed towards Parker Solar Probe and BepiColombo.

Parker Solar Probe and BepiColombo were separated by 3° in latitude, 4° in longitude, and 0.03 au in radial distance at the time of the CME-driven shock arrival at the two spacecraft. The relative proximity of the two probes to each other and to the Sun (~0.365 au) allows us to study the mesoscale structure of CMEs at Mercury's orbit for the first time. We analyse similarities and differences in the magnetic structure of the CME ejecta measured at the two locations, as well as other properties such as shock/sheath characteristics, pitch-angle distributions, and impact of the interaction between the ejecta and its surroundings. Finally, we contextualise our findings within the current discussions on the need to investigate solar transients via spacecraft constellations with small separations, which have been gaining significant attention during recent years.

How to cite: Palmerio, E., Carcaboso, F., Khoo, L. Y., Sánchez-Cano, B., Nieves-Chinchilla, T., Lario, D., Rivera, Y., Pal, S., Stevens, M. L., Salman, T. M., Weiss, A. J., Lee, C. O., Whittlesey, P. L., and Heyner, D.: On the mesoscale structure of CMEs at Mercury's orbit: Parker Solar Probe and BepiColombo observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10112, https://doi.org/10.5194/egusphere-egu23-10112, 2023.

We use the Space Weather Modeling Framework's Alfvén Wave Solar atmosphere Model to simualte the origin and evolution of solar wind plasma during multiple SO and PSP flybys.   Synthetic spectral and narrow band imaging, synthetic spectra and in-situ plasma data are used to study the heating and acceleration of the coronal plasma and solar wind in the inner heliosphere. We identify large scale structures the spacecrafts pass through: current sheet crossings, plasmas of different origins. When data is available we simultaneously simulate non-equilibrium ionization of minor heavy ions in the solar wind along the SO trajectory and study how the plasma charge states represent the different origins of solar wind and also how the out-of-equilibrium charge states change the synthetic remote sensing observations compared to using equilibrium assumptions. 

How to cite: Szente, J., van der Holst, B., and Landi, E.: Context studies of Parker Solar Probe and Solar Orbiter flybys using synthetic in-situ and remote-sensing observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10158, https://doi.org/10.5194/egusphere-egu23-10158, 2023.

The widespread SEP event of 17 April 2021 was observed by five longitudinally well-separated observers in the inner heliosphere covering distances to the Sun from 0.42 to 1 au: BepiColombo, Parker Solar Probe, Solar Orbiter, STEREO A, and close-to-Earth spacecraft. The event, which produced relativistic electrons and protons, was associated with a complex and long-lasting solar eruption involving a long-duration flare, a medium-fast Coronal Mass Ejection (CME), an EUV wave and a complex solar radio burst activity lasting for 40 minutes including type II bursts, marking the presence of a shock, as well as four distinct groups of type III bursts. Our comprehensive analysis of the multi-spacecraft in-situ and remote-sensing observations suggests different source regions for the electron and proton SEP event with a stronger shock contribution for the proton event and a more likely flare-related source of the electron event. We furthermore determine that the four distinct injection episodes, marked by the radio type III burst groups, cover a longitudinal range of about 110° and were a main ingredient for the wide SEP spread. We consider this a new scenario that must be taken into account as a potential contributor to widespread SEP events.

How to cite: Dresing, N., Rodríguez-García, L., Jebaraj, I., Warmuth, A., Wallace, S., Balmaceda, L., Podladchikova, T., Strauss, D. T., Kouloumvakos, A., Palmroos, C., Krupar, V., Gieseler, J., Xu, Z., Mitchell, G., Cohen, C., de Nolfo, G., Palmerio, E., Carcaboso, F., Kilpua, E., and Sanchez-Cano, B.: The reason for the wide particle spread during the 17 April 2021 SEP event, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11319, https://doi.org/10.5194/egusphere-egu23-11319, 2023.

A statistical study of magnetic field power spectra in interplanetary coronal mass ejections (ICMEs) observed by Parker Solar Probe and Solar Orbiter has been performed. The ICMEs had characteristically low proton beta, with values well below unity in all cases. The spectral index was typically near –5/3 and radially invariant in the inertial range, similar to solar wind near the heliospheric current sheet, and steepened to values below –3 in the kinetic range. The break frequency between the inertial and kinetic ranges evolved approximately linearly with radial distance and was closer in scale to the proton inertial length than the proton gyroscale. Magnetic compressibility was invariant with radial distance, in contrast to the solar wind generally. Removal of the background flux rope field gives spectra with shallower slopes at low frequencies (i.e. large spatial scales) and reveals shorter correlation lengths in the magnetic field.

How to cite: Good, S., Rantala, O., Jylhä, A.-S., Chen, C., and Kilpua, E.: Magnetic field spectra of ICMEs observed by Parker Solar Probe and Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11900, https://doi.org/10.5194/egusphere-egu23-11900, 2023.

The solar wind is filled with complex turbulent dynamics that transfer energy from large length scales to progressively smaller scales. This transfer of energy generates a multitude of thin structures, such as current sheets, in the plasma with a preference for forming particularly strong gradients – a property know as intermittency – that are thought to play a role in turbulent dissipation. One of the important problems in the study of solar wind turbulence is understanding how and to what extent the nature of the turbulent dynamics vary as the solar wind expands from the Sun. However, disentangling the dynamical evolution of the turbulence from variations in the properties of different solar wind streams and temporal variations in the source region of a given stream has traditionally been challenging in the solar wind. We make use of a fortuitous alignment between NASA’s Parker Solar Probe and ESA’s Solar Orbiter spacecraft, which occurred at the end of February 2022, to examine how the turbulent fluctuations in the solar wind evolve with radial distance. During this radial alignment the two spacecraft observed the same stream of solar wind plasma, and potentially nearly the same parcel of plasma, at two different radial distances allowing us to separate the evolution with radial distance from the other sources of variability. We explore both the statistical properties of the fluctuations as well as the nature of the most intermittent structures observed by the spacecraft at different length scales in the plasma. The results demonstrate that, while the intermittent fluctuations in the components perpendicular to the radial direction are statistically similar at different radial distances, the intermittency properties in the radial direction can significantly change with distance. Comparisons of the observational results with expanding box simulations of turbulence suggest that some of the key features observed are consistent with the dynamical evolution of spherically polarised Alfvénic fluctuations under the influence of expansion. 

How to cite: Stawarz, J. E., Woodham, L., Laker, R., Matteini, L., Horbury, T., Woolley, T., Bale, S., Perrone, D., Toledo-Redondo, S., Sorriso-Valvo, L., D’Amicis, R., Rivera, Y., and Paulson, K.: The Evolution of Turbulence in the Inner Heliosphere: Insights from the February 2022 Radial Alignment between Parker Solar Probe and Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12288, https://doi.org/10.5194/egusphere-egu23-12288, 2023.

The solar wind, except for the coronal mass ejection events, is traditionally divided into two groups, fast wind and slow wind. However, the origin and releasing mechanism of highly variable slow winds are still a riddle. The slow wind is generally believed to have low Alfvénicity, while the fast wind shows high Alfvénicity. However, Parker Solar Probe shows that highly Alfvénic slow winds take a large proportion of the near-Sun pristine slow winds, suggesting similar sources with the Alfvénic fast winds. Helium abundance (Nα/Np) also bears information about the source region and release mechanism of the slow winds. The typical value of helium abundance in slow winds can be as low as 1% or even lower, while it stays around 4% in fast winds. During its 8th encounter, PSP observed intervals of helium-poor (Nα/Np~0.1%) and helium-normal (Nα/Np~1%) Alfvénic solar winds on two sides of the heliospheric current sheet. We calculate and compare the alpha-particle properties, plasma parameters, collisional age, and magnetic fluctuations in these intervals statistically. In addition, we check the magnetic connection from PSP to the Sun during these intervals with two-step ballistic backmapping. We conclude that the helium-poor winds originate from large quiescent magnetic loops and experience sufficient collisions before and during release. In contrast, helium-normal winds originate from low-latitude coronal holes and experience preferential acceleration and heating due to wave-particle interactions. These results suggest that Alfvénic slow solar winds likely have multiple origins.

How to cite: Wu, Z., He, J., Hou, C., Peng, J., and Duan, D.: Near-Sun Alfvenic Slow Solar Wind with Variable Helium Abundance: PSP observation and source tracing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12976, https://doi.org/10.5194/egusphere-egu23-12976, 2023.

The solar wind is a supersonic plasma flow streamed from the solar corona. The acceleration of the solar wind mainly occurs in the outer corona at heliocentric distances of about 2­–10 R_S (= solar radii), where the coronal heating by magnetohydrodynamic waves and the wave-induced magnetic pressure are thought to play major roles in the acceleration. The mechanisms have not been fully confirmed because the acceleration region is where no spacecrafts have ever reached to date. Recently, however, an inner heliosphere observation network is getting ready, by such as NASA’s Parker Solar Probe and ESA's Solar orbiter and BepiColombo.

Radio occultation observations cover the acceleration region fully and can obtain information complementary to in-situ observations. The radio occultation observations are conducted during the passage of a spacecraft on the opposite side of the sun as seen from the Earth. Inhomogeneity of coronal plasma density structure traversing the ray path disturbs radio waves' frequency, so we can interpret the received frequency fluctuations as density fluctuations in the coronal plasma. Previous observations detected quasi-periodic components thought to represent magnetoacoustic waves (e.g, Efimov et al., 2012; Miyamoto et al., 2014). The details of the detected waves still have not been investigated.

A recent MHD simulation have reproduced the formation of the solar wind based on the wave/turbulence-driven scenario, in which ubiquitous presence of density fluctuation is found. We applied the spectral analysis to the density fluctuations to compare them with the wave components observed by radio occultation observations conducted by JAXA’s Akatsuki spacecraft in 2016. The time-spatial spectrum of density fluctuations has two components whose phase speeds correspond to the Alfvén speed and sound speed, and these two components are considered to be fast and slow modes. The dominant periods of the slow modes in the model are longer than 100 s, which is consistent with the density fluctuations observed by the radio occultation. The periods of the fast modes in the model are about 20–100 s; such short-period components are also seen in the radio occultation observations. These different modes might have been observed by radio occultation simultaneously.

How to cite: Chiba, S., Imamura, T., and Shoda, M.: Density oscillations in the solar corona seen in radio occultation measurements  and a MHD simulation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15607, https://doi.org/10.5194/egusphere-egu23-15607, 2023.

We present an overview of EUV solar observations showing evidence for ubiquitous small-scale jetting activity (i.e., a.k.a. jetlets) driven by magnetic reconnection that might be the primary driver of the solar wind at its source. The jetlets, like the solar wind and the heating of the coronal plasma, are omnipresent throughout the solar cycle. Each event arises from small-scale reconnection of opposite polarity magnetic fields producing a short-lived jet of hot plasma and Alfvén waves into the corona. The discrete nature of the jetlets leads to intermittent outflows from the corona, which homogenize as they propagate away from the Sun and form the solar wind. This discovery establishes the importance of small-scale magnetic reconnection in solar and stellar atmospheres in understanding ubiquitous phenomena such as coronal heating and solar wind acceleration. Based on previous analyses linking the switchbacks to the magnetic network, we also argue that these new observations might provide the link between the magnetic activity at the base of the corona and the switchback solar wind phenomenon. These new observations need to be put in the bigger picture of the role of magnetic reconnection and the diverse form of jetting in the solar atmosphere.

How to cite: Raouafi, N. E., Stenborg, G., Seaton, D. B., Wang, H., Wang, J., DeForest, C. E., Bale, S. D., Drake, J. F., Uritsky, V. M., Karpen, J. T., DeVore, C. R., Sterling, A. C., Horbury, T. S., Harra, L. K., Bourouaine, S., Kasper, J. C., Kumar, P., Phan, T. D., and Velli, M.: Magnetic Reconnection as the Driver of the Solar Wind, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17376, https://doi.org/10.5194/egusphere-egu23-17376, 2023.

One of the most intriguing discoveries of the Parker Solar Probe mission is the presence of magnetic field reversals, known as Switchbacks (SBs), in the near Sun environment. Their origins are still unclear and many mechanisms for their generations have been proposed. On top of that their interactions with the background solar wind turbulence is not yet understood. In this work we investigate whether the SBs can be considered as part of the background solar wind turbulence or as a population of separate structures. We address this problem by studying the distributions of different measures of the turbulence and SBs and their radial evolution. These results are valuable for the understanding of switchbacks formation and of how turbulence affects the generation of structures in the solar wind.  

How to cite: Larosa, A., Chen, C. H. K., McIntyre, J., and Jagarlamudi, V. K.: The interplay between Solar Wind Turbulence and magnetic Switchbacks in the inner Heliospere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17541, https://doi.org/10.5194/egusphere-egu23-17541, 2023.

Onboard the Solar Orbiter spacecraft is the Polarimetric and Helioseismic Imager (SO/PHI), which has two telescopes, a high resolution telescope (HRT) and the full disk telescope (FDT). The instrument is designed to infer the photospheric magnetic field through differential imaging of the polarised light emitted from the Sun. It is the first magnetograph to move out of the Sun-Earth Line, providing excellent stereoscopic opportunities with other ground and space based instruments. Of particular interest is the comparison between SO/PHI-HRT and the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI). They probe the same magnetically sensitive line of Fe1: 6173 Å and have the same aperture diameter. In March 2022 Solar Orbiter crossed the Sun-Earth line, providing an excellent opportunity for a comparison. Here a comparison between the magnetic fields, both line-of-sight and all three vector components, inferred by SDO/HMI and SO/PHI-HRT during the conjunction, are presented. 

How to cite: Sinjan, J., Calchetti, D., Hirzberger, J., Solanki, S. K., del Toro Iniesta, J. C., Woch, J., Gandorfer, A., Alvarez-Herrero, A., Appourchaux, T., Volkmer, R., and Orozco Suárez, D.: Comparison of the Magnetic Field Inferred by SO/PHI-HRT and SDO/HMI, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-424, https://doi.org/10.5194/egusphere-egu23-424, 2023.

Context: Magnetic switchbacks are localised polarity reversals in the radial component of the heliospheric magnetic field. Observations from Parker Solar Probe (PSP) have shown that they are a prevalent feature of the near-Sun solar wind. However, observations of switchbacks at 1 au and beyond are less frequent, suggesting that these structures are dissipated by yet-to-be identified mechanisms as they propagate away from the Sun.

Aims: We estimate the timescales over which magnetic switchbacks may be dissipated by magnetic reconnection and evaluate the viability of reconnection as a dissipation mechanism for switchbacks.

Methods: We analyse magnetic field and plasma data from the magnetometer and Solar Wind Analyser instruments aboard Solar Orbiter between 10 August and 30 August 2021. During this period, the spacecraft was 0.6 – 0.7 au from the Sun.

Results: We identify three instances of reconnection occurring at the trailing edge of magnetic switchbacks. Using hodographs and Walen analysis methods, we find that the reconnection exhaust region for all three events are bound by rotational discontinuities in the magnetic field, consistent with existing models describing the properties of reconnection in the solar wind. Based on these observations, we propose a scenario through which reconnection can dissipate a switchback and we estimate the timescales over which this occurs. We find that for our events the dissipation timescales are much shorter than the expansion timescale and thus, the complete dissipation of all three observed switchbacks would occur well before they reach Earth. Furthermore, assuming the observed reconnection rate has remained constant, and extrapolating back to an origin close to the Sun, we find that the spatial scale of these switchbacks would be considerably larger than is typically seen in the inner heliosphere. Hence, it is implied that the onset of reconnection must occur during transport in the solar wind. If typical, these results suggest that reconnection can play a significant role in dissipating switchbacks and could help explain the relative rarity of switchback observations at 1 au.

How to cite: Suen, G., Owen, C., Verscharen, D., Horbury, T., and Louarn, P.: Magnetic Reconnection as a Dissipation Mechanism for Magnetic Switchbacks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-447, https://doi.org/10.5194/egusphere-egu23-447, 2023.

Context. Interplanetary collisionless shocks are known to be sources of energetic charged particles up to hundreds of MeV. However, the underlying acceleration mechanisms are still under debate.
Aims. We determine the properties of suprathermal protons accelerated by the interplanetary shock on 2021 November 3 with the unprecedented high-resolution measurements by the SupraThermal Electron Proton sensor of the Energetic Particle Detector onboard the Solar Orbiter spacecraft, in order to constrain the potential shock acceleration mechanisms.
Methods. We first reconstruct the pitch-angle distributions (PADs) of suprathermal protons in the solar wind frame. Then, we study the evolution of the PADs, flux temporal profile and velocity distribution function of this proton population close to the shock and compare the observations to theoretical predictions.
Results. We find that the suprathermal proton fluxes peak ∼12 to ∼24 seconds before the shock in the upstream region. The proton fluxes rapidly decrease by ∼50% in a thin layer (∼8000 km) adjacent to the shock in the downstream region and become constant further downstream. Furthermore, the proton velocity distribution functions in the upstream (downstream) region fit to a double power law, f (v) ∼ v^−γ, at ∼1000 − 3600 km s⁻¹, with a γ of ∼3.4 ± 0.2 (∼4.3 ± 0.7) at velocities (v) below a break at ∼1800 ± 100 km s⁻¹ (∼1600 ± 200 km s⁻¹) and a γ of ∼5.8 ± 0.3 (∼5.8 ± 0.2) at velocities above. These indices are all smaller than predicted by first-order Fermi acceleration. In addition, the proton PADs show anisotropies in the direction away from the shock in the close upstream region and become nearly isotropic further upstream, while downstream of the shock, they show a clear tendency of anisotropies towards 90^◦ PA.
Conclusions. These results suggest that the acceleration of suprathermal protons at interplanetary shocks are dynamic on a time scale of ∼10 seconds, i.e., few proton gyro-periods. Furthermore, shock drift acceleration likely plays an important role in accelerating these suprathermal protons.

How to cite: Yang, L., Heidrich-Meisner, V., Berger, L., Wimmer-Schweingruber, R., Wang, L., He, J., Zhu, X., Duan, D., Kollhoff, A., Pacheco, D., Kühl, P., Xu, Z., Keilbach, D., Rodríguez-Pacheco, J., and Ho, G.: Acceleration of Suprathermal protons near an Interplanetary Shock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2236, https://doi.org/10.5194/egusphere-egu23-2236, 2023.

The Spectrometer/Telescope for Imaging X-rays (STIX) on-board Solar Orbiter measures the X-ray photons emitted by thermal and non-thermal electrons via bremsstrahlung mechanisms. STIX modulates the incident radiation by means of 30 sub-collimators that provide information on the complex values of specific Fourier components of the flaring X-ray source. This talk will illustrate this data formation process and explain how this model can be exploited to formulate image reconstruction methods including constrained maximum entropy, multi-scale CLEAN, feature augmentation, and Particle Swarm Optimization for parametric imaging. These methods will be applied against several experimental STIX observations and the reliability of the reconstructed morphologies will be validated by comparison with EUV maps recorded by the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory.

How to cite: Piana, M., Massa, P., Volpara, A., Massone, A. M., Benvenuto, F., Perracchione, E., Battaglia, A. F., Hurford, G., and Krucker, S.: The STIX imaging concept: model for data formation and image reconstruction methods for the Spectrometer/Telescope for Imaging X-rays on-board Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2688, https://doi.org/10.5194/egusphere-egu23-2688, 2023.

Upflows in the corona are of importance as they may contribute to the solar wind. Because of this, there has been interest
in the analysis of upflows at the edges of active regions (ARs). The coronal upflows that are seen at the edges of ARs have coronal
elemental composition and can contribute to the slow solar wind. The sources of the upflows have been challenging to determine
because they may be multiple.

In this talk, we will discuss the latest results of coronal upflows. This includes an example which is found unusually close to a sunspot umbra and unusually has photospheric abundance. We analyse in detail the cause of this upflow region using a combination of Solar Orbiter EUV images at high spatial and temporal resolution,
Hinode/EUV Imaging Spectrometer data, and observations from instruments on board the Solar Dynamics Observatory. This com-
bined dataset was acquired during the first Solar Orbiter perihelion of the science phase, which provided a spatial resolution of 356
km for 2 pixels.  In the location of the, a small positive polarity connects to the umbra
via small-scale and very dynamic coronal loops.  The Solar Orbiter EUV Imagers (EUI) high resolution data show the dynamics of these small loops, which last on timescales of only minutes. This is the location of the coronal upflow which has photospheric abundance. We attempt to determine if it is possible that they can feed into the slow solar wind. We discuss future observation potential using Solar Orbiter data along with data from other missions and ground-based observatories. This provides opportunities for multiple viewpoints, multi-wavelength measurements of these upflow regions.

How to cite: Harra, L., Mandrini, C., and Brooks, D. and the Solar Orbiter EUI collaborators: The source of unusual coronal upflows with photospheric abundance in a solar active region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3094, https://doi.org/10.5194/egusphere-egu23-3094, 2023.

The fundamental science objective behind solar X-ray imaging spectroscopy is to gain information on the electrons accelerated by magnetic reconnection and on the temperature of the correspondingly heated plasma throughout the whole flaring volume. This talk will prove that the visibility-based technology at the base of the Spectrometer/Telescope for Imaging X-rays (STIX) allows the construction of electron flux and differential emission measure maps that are nicely smoothed along the energy and temperature directions, respectively. Using this approach, we will perform a spatially resolved analysis of the electron flux spectra associated with hard X-ray emissions measured by STIX and discuss the spatially resolved consistency of such emissions with a thermal distribution of the electrons in the flaring source.

How to cite: Volpara, A., Massa, P., Massone, A. M., and Piana, M.: Spatially resolved imaging spectroscopy with the Spectrometer/Telescope for Imaging X-rays on-board Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3618, https://doi.org/10.5194/egusphere-egu23-3618, 2023.

The propagation and radial evolution of energetic particle events can only be studied by multiple-point simultaneous in-situ measurement within the heliosphere.  The joint ESA/NASA Solar Orbiter mission that was launched in February 2020, is designed to study the Sun and inner heliosphere in greater detail than ever before.  The Energetic Particle Detector (EPD) investigation on Solar Orbiter is a suite of four different sensors that measure the energetic particles from slightly above solar wind energies to hundreds of MeV/nucleon. Since launched, EPD already observed numerous large solar energetic particle (SEP) and energetic storm particle (ESP) events inside of 1 au in greater temporal and spectral resolutions than ever before.  Many of these events were also measured by spacecraft at 1 au such as ACE and/or STEREO. 

On April 2, 2022, an active region (AR 12975) on the western limb (W80) of the Sun produced a large SEP event and associated fast moving (>1400 km/s) coronal mass ejection (CME) and a CME-driven interplanetary shock (~1900 km/s).  During that time, the Solar Orbiter spacecraft was cruising near its perihelion distance (~0.35 au) at W109 relative to the Earth-Sun line, and the STEREO Ahead spacecraft was at E35.  Together, the particle instruments on these probes measured the SEP/ESP and the plasma and field instruments detected the associated interplanetary shock/CMEs on April 2-3, 2022.  In this paper, we report the multi-spacecraft observations of this event that were measured by Solar Orbiter, and we discuss the propagation and transport of SEPs from 0.3 to 1 au.

How to cite: Ho, G., Mason, G., Allen, R., Kouloumvakos, A., Wimmer-Schweingruber, R., Rodríguez-Pacheco, J., and Gómez-Herrero, R.: April 3, 2022 in-situ ESP event as observed by Solar Orbiter, ACE and Stereo, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4385, https://doi.org/10.5194/egusphere-egu23-4385, 2023.

Solar energetic particle (SEP) observations from Suprathermal Ion Spectrograph (SIS) which is part of the Energetic Particle Detector (EPD) suite on board the Solar Orbiter (SolO) mission, provide an unprecedented opportunity to study the composition and evolution of SEPs close at the Sun and to understand where SEPs are accelerated at the Sun and when released from their sources to interplanetary space. In this study, we examine ³He-rich time periods that last for many days. These extended ³He-rich periods that observed by SIS are particularly interesting because this rare isotope of He is not abundant in the solar corona and events rich of ³He are usually associated with transient and small "impulsive" SEP events. First, we compile a catalogue of extended ³He-rich time periods that were observed during the first three years of SolO mission and we determined and registered their characteristics (duration, composition, etc.). We also examined the spacecraft’s magnetic connectivity during these time periods and the characteristics of the connected regions. We find that, during the extended ³He-rich time periods, SolO is stably magnetically connected to an active region(s) for most cases. The connectivity usually changes near the boundaries of the time periods so the connectivity to the source region is an important element for the observation of these ³He-rich time periods. The active region(s) where SolO is magnetically connected during the time periods are typically very productive of solar events (flares, jets, CMEs). 

How to cite: Kouloumvakos, A., Mason, G. M., Ho, G. C., Allen, R. C., Rouillard, A. P., Rodríguez-Pacheco, J. R., Wimmer-Schweingruber, R. F., and Gómez-Herrero, R.: Extended 3He-rich time periods observed by Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4615, https://doi.org/10.5194/egusphere-egu23-4615, 2023.

How to cite: Awasthi, A. K., Mrozek, T., Litwicka, M., Steslicki, M., Kolomanski, S., and Kulaga, K.: Thermal-nonthermal energy partition in weak flares observed by STIX, XSM, and SDO, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4805, https://doi.org/10.5194/egusphere-egu23-4805, 2023.

Any spacecraft immersed into the solar wind builds up a non-zero electric potential with respect to the local environment by continuously collecting the charged particles from ambient plasma populations and emitting additional charged particle populations, namely photo-electrons and/or secondary electrons, from its surface materials. These newborn electrons of spacecraft origin as well as the electric fields induced in the vicinity of the spacecraft body by the so called spacecraft potential may in turn significantly distort the local plasma conditions and therefore affect any in-situ electron observations and thus potentially modify the derived electron properties. Here we present an observational analysis of these effects as seen by the SWA-EAS electron analyser in the variable plasma and electrostatic environment of the Solar Orbiter spacecraft. We provide some characteristic properties of these parasitic electron populations in order to later develop possible correction methods applied to the SWA-EAS measurements for deriving unperturbed ambient plasma properties. The analysis is performed on a statistical basis using a large set of SWA-EAS 3D electron velocity distribution functions and in comparison to other relevant in-situ measurements acquired namely by other two complementary on board plasma instruments – SWA-PAS and RPW.

How to cite: Stverak, S., Herčík, D., Hellinger, P., Nicolaou, G., Owen, C., and Maksimovic, M.: Photoelectrons and spacecraft potential effects on SWA-EAS electron measurements on board the Solar Orbiter spacecraft, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5652, https://doi.org/10.5194/egusphere-egu23-5652, 2023.

Using the magnetic field properties in the interplanetary medium and near the Sun allows to trace back the trajectory of an in-situ observed parcel of solar wind. This kind of study has already shown around 1 AU an anti-correlation between the speed of the wind, and both the expansion factor of the flux tube and the magnetic field magnitude of the source (Wang & Sheeley 1990). In this study we apply the magnetic connectivity to the Solar Orbiter measurements from 0.3 AU to 1 AU, to trace back their source at the solar surface using ADAPT magnetograms. The nominal mission phase data are used (from the beginning of 2021). To better approximate the departure time of the plasma at the Sun and the location of its source, we constrain the trajectory of the solar wind using iso-poly modeling (Dakeyo et al. 2022) from the probe location until the source surface Rss. In addition, we aim to follow the classification of Maksimovic et al. 2020 and Dakeyo et al. 2022, to extrapolate sunward the magnetic condition of the different wind speed populations observed by Solar Orbiter.  This statistical analysis shows that the correlation already observed at 1 AU mentioned above (bulk speed, flux tube expansion and magnitude of the magnetic field) are globally conserved getting closer the Sun between 0.3 AU and 1 AU. Depending the speed of the wind we are also able to estimate typical values of expansion factor, magnitude of the coronal magnetic field, the state of charge for each wind speed populations.

How to cite: Dakeyo, J.-B., Rouillard, A., Maksimovic, M., Réville, V., Louarn, P., and Démoulin, P.: Statistical study of the solar wind properties using the magnetic connectivity from in-situ measurements of Solar Orbiter extrapolated sunward the Solar Corona., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6664, https://doi.org/10.5194/egusphere-egu23-6664, 2023.

We present an updated procedure developed to calibrate flight data from the Electron Analyser System (EAS) of the Solar Wind Analyzer (SWA) instrument onboard Solar Orbiter. By imposing specific physical conditions on the data set, like isotropy of the core electron population, and by comparing electron fluxes measured by the two EAS heads, we are able to derive consistent correction factors of the raw data set. The procedure is shown to improve the quality of the merging of the two heads dataset. We evaluate the impact of these corrections on ground moment calculation and on specific features of the electron pitch-angle distributions during the first perihelia of the mission. Anisotropy of the component of the pitch-angle electron distribution in different energy ranges is analysed. Detailed properties of specific features of the distribution including strahl and anti-strahl electrons are examined with this updated procedure.

How to cite: Berthomier, M., Lenc, A., Nicolaou, G., Owen, C., Lewis, G., Wicks, R., Fortunato, V., and Horbury, T.: Electron distribution functions measured by the SWA/EAS sensor during the first perihelia of the Solar Orbiter mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6792, https://doi.org/10.5194/egusphere-egu23-6792, 2023.

Impulsive electron events observed in interplanetary space are believed to be generated by acceleration in solar flares. This notion has been supported by correlations between the characteristics of energetic electrons detected in-situ near 1 au and those in solar flares derived from hard X-ray observations. However, the details of this relation are still unclear, presumably because of the complex combination of acceleration, injection, and transport effects that are involved.

We present the first statistical results on impulsive electron events obtained by joint observations of remote-sensing and in-situ instruments on Solar Orbiter. We use the suite Energetic Particle Detector (EPD) to measure the properties of the electrons (time profile, anisotropy, maximum energy, inferring the injection time at the source, etc.), as well as to determine the particularities of the composition in the suprathermal energy range. Also, X-ray observations from the Spectrometer/Telescope for Imaging X-rays (STIX) constrain the energetic electrons in the solar flare in terms of timing, spectrum, and location. Type III radio bursts detected by the Radio and Plasma Waves (RPW) instrument are used to link the nonthermal X-ray peaks to the interplanetary electron beams. Finally, the Extreme Ultraviolet Imager (EUI) provides context on the flare evolution. We use a large event sample obtained during the first 2.5 years of the Solar Orbiter mission, which covers a wide range of radial distances ranging from as close as 0.33 au to 1.02 au.

How to cite: Warmuth, A., Schuller, F., Gómez-Herrero, R., Rodríguez-Pacheco, J., Carcaboso, F., Krucker, S., Pacheco, D., Wimmer-Schweingruber, R., Kollhoff, A., Dresing, N., Fedeli, A., Paipa, D., Maksimovic, M., Vilmer, N., Barczynski, K., Podladchikova, O., Mason, G., and Rouillard, A. and the Joint STIX-EPD-RPW-EUI Working Group: First results on interplanetary electron events obtained by joint observations of remote-sensing and in-situ instruments on Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7482, https://doi.org/10.5194/egusphere-egu23-7482, 2023.

Spacecraft observations made at 1 AU from the Sun showed that the solar wind parameters are highly variable. D’Amicis and Bruno (2015) suggested that two solar wind regimes can be distinguished according to the nature of the embedded turbulent fluctuations. If the velocity and magnetic field variations are strongly correlated, Alfvénicity of the fluctuations is high, thus the first solar wind regime is called Alfvénic. Its characteristics suggest that it probably originates from coronal holes. The alpha particle parameters correspond to those usually associated with the fast solar wind. The alpha relative abundance is high (about 4 %) and alpha particles are faster and hotter than protons. The second solar wind regime has embedded non-Alvénic fluctuations. It could come from coronal streamers, but its formation remains unclear. Observations at 1 AU show that the non-Alvénic wind typically has the small alpha-proton relative drift and nearly equal temperature of both ionic components. In our study, we focus on variations of the alpha particle parameters in the non-Alvénic wind and on changes during transition from the Alfvénic to non-Alfvénic winds. We found observations of alpha particles slower than protons, for example near the termination of the corotating rarefaction regions. Using the WIND measurements, we perform a statistical study and compare the plasma properties associated with different ranges of the alpha-proton relative drift. Furthermore, we use measurements from the WIND and Solar Orbiter missions to study changes of the non-Alfvénic wind with increasing distance from the Sun. We discuss their possible origin both in terms of formation near the Sun and during propagation through the interplanetary space.

How to cite: Durovcova, T., Šafránková, J., and Němeček, Z.: Variations of alpha particle parameters in the non-Alvénic wind, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8088, https://doi.org/10.5194/egusphere-egu23-8088, 2023.

We report a partial filament eruption in the southern solar hemisphere that occurred on 18 March 2022 during the first science perihelion of Solar Orbiter. The filament erupted into a coronal mass ejection (CME), producing coronal dimmings at the footpoints of the erupting structure. The expanding dimming then merged with the adjacent southern polar coronal hole. This merging of two open magnetic structures is observationally rare and poorly understood. We use remote sensing data from multiple co-observing spacecraft to understand the physical processes during this merging event. The evolution of the merger is examined using Extreme-UltraViolet (EUV) images obtained from the instruments onboard the Solar Orbiter and Solar Dynamic Observatory spacecraft. The plasma dynamics are quantified using spectroscopic data obtained from the EUV Imaging Spectrometer onboard Hinode. The preliminary results show that the coronal hole and coronal dimming become indistinguishable from each other after the merging. Several plasma upflow regions were observed throughout the merging event, suggesting the opening of magnetic field lines. The brightening of bright points and coronal jets inside the merged region further imply ongoing reconnection processes. This work also has implications for the formation of coronal hole/open field regions and the origin of solar wind from coronal dimming and coronal hole boundaries.

How to cite: Ngampoopun, N., Long, D., Baker, D., Green, L., Yardley, S., James, A., and To, A.: The Merging of a Coronal Dimming with the Southern Polar Coronal Hole During Solar Orbiter’s First Perihelion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8269, https://doi.org/10.5194/egusphere-egu23-8269, 2023.

The ESA/NASA Solar Orbiter mission performed its first close solar encounters at 0.32 au in March 2022 and at 0.29 au in October 2022. By combining high-resolution imaging and spectroscopy of the Sun with detailed in-situ measurements of the surrounding heliosphere, Solar Orbiter enables us to study the Sun's corona in unprecedented detail, and determine the linkage between observed solar wind streams and their source regions on the Sun. Its science return will be enhanced significantly by coordinated observations with other space missions, e.g. Parker Solar Probe, as well as new ground-based telescopes like DKIST. Over the course of the 10-year mission, Solar Orbiter's highly elliptical orbit will get progressively more inclined to the ecliptic plane. Thanks to this new perspective, Solar Orbiter will deliver images and comprehensive data of the unexplored Sun’s polar regions and the Sun's far side. This talk will provide a status update of the mission and the science operations performed during the first two science perihelia, and summarise early science results.

How to cite: Zouganelis, Y., Müller, D., De Groof, A., Williams, D., Walsh, A., Janvier, M., Nieves-Chinchilla, T., Lario, D., and Musset, S.: Solar Orbiter: The Sun up close, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8923, https://doi.org/10.5194/egusphere-egu23-8923, 2023.

Mini-filament eruptions are one of the most common small-scale transients in the solar atmosphere. However, their eruption mechanisms are still not understood thoroughly. Here, with a combination of 174 Åimages of high spatio-temporal resolution taken by the Extreme Ultraviolet Imager on board Solar Orbiter and images of the Atmospheric Imaging Assembly on board Solar Dynamics Observatory, we present a detailed investigation of an erupting mini-filament over a weak magnetic field region on 2022 March 4. It is clearly observed that, as the mini-filament quickly ascends, two ribbons appear underneath it. Subsequently, when the erupting mini-filament interacts with the outer ambient loops, some dark materials blow out, forming a blowout jet characterized by a widening spire. At the same time, multiple small bright blobs of size 1–2 Mm appear at the interaction region and propagate along the post-eruption loops towards the footpoints of the erupting fluxes at a speed of  100 km s􀀀1, as well as giving rise to a semi-circular brightening. These features indicate that the mini-filament eruption first undergoes the internal and then external reconnection, the latter of which mainly transfers mass and magnetic flux of the erupting mini-filament to the ambient corona.

How to cite: Li, Z., Cheng, X., Ding, M., Chitta, P., Peter, H., and Berghmans, D.: Evidence for External Reconnection Between an EruptingMini-filament and Ambient Loops Observed by Solar Orbiter/EUI, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9221, https://doi.org/10.5194/egusphere-egu23-9221, 2023.

The Spectral Imaging of Coronal Environment (SPICE; SPICE Consortium et al. 2020) provides an extraordinary opportunity to study the chromosphere and transition region using EUV wavelengths, e.g., Ne VIII 770 Å, C III 977 Å, O VI 1032 Å, and Lyman-β 1025 Å. We present preliminary results modeling Ne VIII 770 Å intensity using images from SPICE and the COronal DEnsity and Temperature (CODET) model. This model is based on relationships between the magnetic field, density, and temperature. It uses a flux transport model, the Potential Field Extrapolation model (PFSS), an emission model based on Chianti atomic database 10.0.2, and an optimization algorithm. In addition, we assume that the emission from the top of the transition region (Ne VIII 770 Å) can be described using the magnetic field in the coronal base at 1.014 R_Sun (from PFSS).

How to cite: Rodríguez Gómez, J. M., Kucera, T., and Young, P.: Modeling EUV intensity at the top of the transition region using SPICE data on board Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9380, https://doi.org/10.5194/egusphere-egu23-9380, 2023.

We report Solar Orbiter observations of six recurrent solar energetic particle injections in 2022 March 3–6 at ~0.5 au. The injections were associated with jets emanating from a plage near a large sunspot in NOAA active region 12957. We saw large jets in injections with high ³He and Fe enrichments and minor jets in injections with no or lower enrichments. Furthermore, the event with the highest enrichment showed a more compact configuration of the underlying photospheric magnetic field. The higher fluences as well as harder spectra were seen in the event with a wider jet-like eruption. However, in this case, the buildup time might be required to produce such spectra. Extreme ultraviolet images from Solar Orbiter revealed a crisscrossing network at the base of jets not seen from 1 au that might be suitable for the recurrent events.

How to cite: Bucik, R., Mason, G. M., Nitta, N. V., Krupar, V., Rodriguez, L., Ho, G. C., Hart, S. T., Dayeh, M. A., Rodríguez-Pacheco, J., Gómez-Herrero, R., and Wimmer-Schweingruber, R. F.: Recurrent 3He-rich solar energetic particle injections observed by Solar Orbiter at ~0.5 au, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9386, https://doi.org/10.5194/egusphere-egu23-9386, 2023.

In this paper we will present preliminary results of an X-ray flare that occurred on 9^th May 2021 for which the thermal and non-thermal X-ray signatures were detected both from the Earth direction by Fermi/GBM  and by STIX on Solar Orbiter at 97° from the Sun-Earth line.  This flare was also well observed in radio with the ground-based instruments  in Nançay and in the interplanetary space by WIND/WAVES and RPW on Solar Orbiter . The X-ray event shows both an impulsive phase observed above 25 keV by STIX and FERMI and followed by a more gradual phase observed up to 15 keV by both STIX and FERMI. In the decimetric/metric radio domain, this event shows a group of type III bursts extending to the interplanetary medium as well as type IV emission.  We shall discuss here the relative temporal evolutions of HXR emissions at different energies with those of the radio fluxes at different frequencies, as well as the spatial evolution of the X-ray and radio sources during the different phases of the event. We shall also investigate the evolution of the characteristics of the non-thermal electrons detected in the corona associated to both implusive and gradual phase of the flare.

How to cite: Vilmer, N., Musset, S., Zhang, M., Klein, K.-L., and Paipa, D.: Energetic electrons in the solar corona  for the long duration event of 9 May 2021 as diagnosed from X-ray and radio observations., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11354, https://doi.org/10.5194/egusphere-egu23-11354, 2023.

In this work the analysis of the SOL2022-03-30 X1.4 GOES class flare is presented. This flare was observed by Solar Orbiter during perihelion as well as from Earth based observatories including SDO’s AIA and the Extended Owens Valley Solar Array (EOVSA). It displays well correlated fast time variation in the HXR and microwave wavelengths of emission with time dependent lags. The mechanism behind such observed puslations is not yet fully understood and is important for gaining an understanding of particle acceleration and energy release in solar flares. In this flare, the oscillatory behaviour grows in time and can be split into three phases with QPP periods ~7s, ~14s and ~35s. New capabilities from Solar Orbiter’s Spectrometer Telescope for Imaging X-rays (STIX) allows for the localisation of individual bursts on short timescales which enables us to determine the spatial morphology of the HXR emission and its evolution in time. The HXR source locations are compared with the microwave sources observed by EOVSA and the ribbon structure determined from AIA 1600Å and 1700Å. The QPP source locations are found to change significantly in time. Furthermore, the electron spectral index is anti-correlated with the observed HXR emission, obeying the soft-hard-soft relation. When combined, these observations point towards a mechanism for QPP generation which involves quasi-periodic energy release and injection of electrons into the flaring loop. However, several open questions remain about how these QPPs are generated.  

How to cite: Collier, H., Hayes, L., Battaglia, A., Harra, L., and Krucker, S.: SOL2022-03-30 X1.4 GOES Class Flare: Localising the source of quasi periodic pulsations in the Hard X-ray and microwave emissions with STIX onboard Solar Orbiter and EOVSA., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11801, https://doi.org/10.5194/egusphere-egu23-11801, 2023.

With the launch of Solar Orbiter (SolO) on Feb. 10th 2020, a new era of multi-spacecraft solar energetic particles (SEP) observations has started. The unique orbit of the mission allows the observation of SEP events close to the Sun (<0.28 au), which can occasionally be compared to corresponding observations made by other spacecraft at 1au. Such multi-spacecraft observations of the same event at different radial distances provide an excellent opportunity to study the radial evolution of SEP events.

In this study, we identify SEP events for which SolO and either Wind or STEREO-A had a small longitudinal separation (<15°) between their magnetic foot-points at the Sun. For all SEP events that satisfy our selection criteria we determine the onset times and rise times as well as peak fluxes and peak values of the first-order anisotropy for electrons in the energy range from ∼50−85 keV. We compare the event parameters observed at the different spacecraft regarding their radial changes. In our sample we find strong event-to-event variations in the radial dependency of all derived event parameters. For the majority of events, the peak flux and the maximum value of the first-order anisotropy decrease with increasing radial distance to the Sun, while the rise time increases with radial distance in the majority of events. The derived onset delays observed between two spacecraft were found to be too long to be explained by ideal Parker spirals in multiple events.

We present an overview of the most interesting observations and discuss the wide variability in the radial dependency of the event parameters analysed in this study.

How to cite: Kollhoff, A., Berger, L., Brüdern, M., Dresing, N., Eldrum, S., Fleth, S., Gómez-Herrero, R., Heber, B., Kühl, P., Pacheco, D., Rodríguez-García, L., Rodríguez-Pacheco, J., Wimmer-Schweingruber, R. F., and Xu, Z.: Multi-spacecraft observations of near-relativistic electron events at different radial distances, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12027, https://doi.org/10.5194/egusphere-egu23-12027, 2023.

The slow solar wind can be separated into at least two different components: a dense, variable wind produced by helmet streamers and a more tenuous and Alfvénic component emitted by coronal holes. Previous studies have shown that the slow Alfvénic wind is associated with enhanced alpha particle abundances, strong proton beams, and large alpha-to-proton temperature ratios: typical properties of the fast wind known to originate from inside large coronal holes. Recent combined in-situ and remote-observation campaigns by the Solar Orbiter mission exploiting the Proton and Alpha particle Sensor (SWA-PAS) can help us to study the relationship between the Alfvénic slow wind and coronal holes. We exploit these latest observations in conjunction with the newly-developed multi-species IRAP Solar Atmospheric Model (ISAM) model to study the coronal conditions that favour the production of an Alfvénic slow wind. ISAM simulates the coupled transport of both neutral and charged particles between the chromosphere and the corona, including a self-consistent treatment of collisional and ionisation processes, as well as detailed energy and heat flux conservation equations. In this study we discuss how the simulated alpha to proton ratios are modulated in response to different coronal heating rates and discuss these simulation results in light of recent Solar Orbiter measurements. The results presented here were funded by the European Research Council through the SLOW SOURCE project grant number DLV-819189.

How to cite: Thomas, S., Rouillard, A., Lavarra, M., Poirier, N., and Blelly, P.-L.: Investigating the Source of the Slow Solar Wind Using Solar Orbiter Observations and the IRAP Solar Atmospheric Model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12502, https://doi.org/10.5194/egusphere-egu23-12502, 2023.

Flare-associated particles from so-called impulsive events might be efficiently reaccelerated in gradual Solar Energetic Particle (SEP) events which are typically related to coronal mass ejections (CMEs). The existence and characteristics of such a flare-associated seed population might play a key role for understanding the high variability in particle intensity under comparable CME speeds and solar wind conditions. Understanding this variability will improve predictions of large gradual SEP events that cause a severe risk for satellite and even ground-based infrastructure. We analyze a sequence of impulsive and subsequent gradual events that occurred between 5 and 11 March 2022 and were measured in-situ with Solar Orbiter at a close distance of 0.5 AU to the Sun. We study in detail the behavior of suprathermal ions during the events and relate it to the ambient solar wind plasma properties and remote-sensing observations of the respective flares and CMEs observed from SOHO, SDO, and Solar Orbiter. We find in particular a strong local enhancement of suprathermal flare-associated ions that are trapped for several hours between two ICME structures and provide therefore a natural reservoir of seed particles that can be efficiently further accelerated in ambient compression regions or occurring shocks on their way out to 1 AU.

How to cite: Janitzek, N., Moraleda, M., Walsh, A., Mason, G., Gomez-Herrero, R., Kollhoff, A., Pacheco, D., Barcynski, K., Rodríguez-García, L., Musset, S., Hayes, L., Zouganelis, I., Ho, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Behavior of Flare-associated Suprathermal Ions at Coronal Mass Ejections observed with Solar Orbiter at 0.5 AU, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13249, https://doi.org/10.5194/egusphere-egu23-13249, 2023.

   Energy spectra of X-ray solar flares observed by the Spectrometer-Telescope for Imaging X-rays (STIX) onboard the Solar Orbiter consist of both thermal and non-thermal parts. The thermal part is present in all solar events. When the non-thermal part of the energy spectrum begins to dominate, we can expect detection in interplanetary space of high-energy electron beams that have escaped the coronal loops. When hard X-ray flares are detected solar type III radio bursts are registered frequently with their numerous modifications like drift pairs, U-type, and structured bursts. The e-CALLISTO simple worldwide radio antenna stations allow us to identify the existence of non-thermal components in the energy spectra of strong X-ray flares. At the same time, some X-ray flares are accompanied by ejections of energetic ions including heavy ions. The specific features in X-ray bursts responsible for events with simultaneous light and heavy particle stream generation are still unclear compared with those with electron emission only.

    We present preliminary results of observations gathered in December 2022 and cross-analysis of data on energetic light and heavy particle fluxes and X-ray flare parameters. The end of 2022 was distinguished by moderate to high solar activity, the presence of three periods with enhanced proton and heavy-ion fluxes at the beginning of the month, in the middle, and on 25-26 December. We demonstrate also the presence of narrow directed electron beams detected by the Electron Proton Telescope (EPT) of EPD for selected events mentioned above, and heavy ions detected by the Suprathermal Ion Spectrograph (SIS) of EPD.

How to cite: Dudnik, O., Mason, G., Ho, G., Allen, R., Wimmer-Schweingruber, R., Rodríguez-Pacheco, J., Espinosa Lara, F., Gómez Herrero, R., Mrozek, T., and Karlicky, M.: Heavy-ion-rich X-ray solar flares in December 2022 measured on Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13609, https://doi.org/10.5194/egusphere-egu23-13609, 2023.

During nearly three years of operation, STIX aboard Solar Orbiter observed thousands of flares.   Many of them were simultaneously observed by Solar X-Ray Monitor (XSM) on board Indian Chandrayaan-2 circling the Moon.  We present results of a multi-wavelength study for  one selected flare  of M GOES class as seen from 1.a.u. STIX data provided  the opportunity for a detailed analysis of hard X-ray emission in several energy bands including the light curves, reconstructed hard X-ray images and spectra. The differential emission measure diagnostics of the flaring plasma have been carried out based on interpretation of the XSM X-ray spectra. Using the differential evolution (DE) approach we have determined the “full” model of emitting source including the temperature, emission measure and elemental abundances as determined simultaneously throughout the flare.  We discuss patterns of elemental composition history for individual plasma temperature components.

How to cite: Kepa, A., Siarkowski, M., Awasthi, A. K., Sylwester, B., and Sylwester, J.: A multi-thermal analysis of M-class flare observed  in common by STIX and XSM, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13784, https://doi.org/10.5194/egusphere-egu23-13784, 2023.

Solar Hard X-Ray (HXR) emission is observed typically in the form of localized, rather compact sources. Majority of these sources are flare related, however there is growing evidence, observational and theoretical, that we can expect HXR emission from places not directly related to primary energy release regions. From this point of view, failed eruptions are phenomena which are very interesting. Failed eruptions are events which at an early phase develop like a typical eruption which evolves into CME. However, for unclear reasons these eruptions stop abruptly somewhere in the solar corona. Many mechanisms are suspected to be responsible for stopping an eruption i.e. kink instability leading to stable configuration of erupting flux tube, magnetic tension within erupting structure or interaction and reconnection with an overlying coronal magnetic field. The last one may lead to electron acceleration and production of high temperature regions emitting in the HXR. There are only a few observations, from past instruments, showing some evidence of HXR production in failed eruptions. Recently, the Solar Orbiter has been launched giving a completely new perspective for observation and analysis of coronal dynamic events. Apart from others, it carries onboard Extreme-Ultraviolet Imager (EUI) and Spectrometer/Telescope for Imaging X-rays (STIX) telescopes open an opportunity to understand the physics of failed eruptions. The new EUV and HXR observations are important for at least two reasons. First, SO can approach the Sun closer than 0.3 a.u. which increase spatial resolution and sensitivity of telescopes, giving ocasion for registering weak HXR sources which can not be observed with previous instruments. Second, SDO/AIA instrument operating on the Earth orbit can provide stereoscopic context for SO/EUI images which may help to investigate deeper the geometry of the eruption and causes of its braking. Here, we present a very well observed flare accompanied by a failed eruption. The event occurred when longitudinal separation of the Earth and SO was 17 degrees. From the Earth perspective the event was visible very close to the west limb of a solar disc. For SO it was a behind-the-limb event with occulted footpoints which gave us a very good view, especially in the HXR range, of emission coming from the solar corona. During a flare's impulsive phase, the eruption accelerated to the velocity of a few hundreds kilometers per second and after six minutes it stopped abruptly at the height of 100 000 km above the solar surface. The eruption reconnected with overlying coronal loops leading to occurrence of at least three regions observed by STIX. The lowest source seems to be a typical, flare related coronal source, possibly consisting of two spatially unresolved sources located close to the primary reconnection site. The other two sources are located higher in the corona where reconnection of the eruption with an overlying magnetic field was observed. These sources behave significantly differently than the lowest source. Namely, their evolution is more gradual and seems to be driven by direct heating not the evaporation of chromospheric plasma which is a case for the lowest source.

How to cite: Mrozek, T., Stęślicki, M., Kołomański, S., and Barczyński, K.: Triple coronal Hard X-Ray source observed by STIX during a failed eruption of a filament., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14396, https://doi.org/10.5194/egusphere-egu23-14396, 2023.

Solar Orbiter is an ESA-led mission of international collaboration with NASA to investigate how the Sun creates and controls the heliosphere, and why solar activity changes with time. One of its top-level science questions is how solar eruptions produce energetic particle radiation that fills the heliosphere. With its four viewing directions the High-Energy telescope (HET) provides critical information about the sources and transport of high-energy particles.

This study analyses relativistic electron measurements obtained by HET in the energy range from 200 keV to above 10 MeV. The purpose of this study is to analyse anisotropies of relativistic solar energetic electrons utilizing the different viewing directions of HET. Time periods with enhanced fluxes of relativistic electrons, have been identified. A list of these time periods including additional observations such as maximum energy and flux as well as the first order anistropy will be presented. This is the first time since the Helios mission that anisotropies of high energy electrons have been measured.

How to cite: Fleth, S., Kühl, P., Kollhoff, A., Wimmer-Schweingruber, R. F., Heber, B., Rodríguez-Pacheco, J., and Dresing, N.: Anisotropies of solar energetic electrons in the MeV range measured with SolO/EPD/HET, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14698, https://doi.org/10.5194/egusphere-egu23-14698, 2023.

Solar flares are efficient accelerators of energetic particles, mainly electrons, which transport energy from reconnection site to the chromosphere. Energetic electrons are thermalized in the chromosphere and produce hard X-ray emission (HXR) following the thick-target bremsstrahlung mechanism. The thick-target model predicts that altitude of the HXR sources in the footpoints of solar flare decreses with incresing energy. The relation was registered for the solar flares observed with Yohkoh/HXT and RHESSI. In our research, we investigated the energy-altitude relation in flare footpoints in a group of strong (>M1.0 GOES class) events recorded by the Spectrometer/Telescope for Imaging X-rays (STIX) onboard the Solar Orbiter. Here we present the results of analysis of the relation obtained from STIX data, e.g. temporal evolution and density distributions on selected examples. Thanks to unprecedented high temporal and spatial resolutions  of STIX data, we can trace changes of plasma dynamics in footpoints like never before.

How to cite: Mikuła, K. and Mrozek, T.: The energy-altitude relation in solar flare footpoints observed by STIX, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14916, https://doi.org/10.5194/egusphere-egu23-14916, 2023.

The electrons in the solar wind exhibit non-thermal velocity distribution functions. Observed non-thermal features of the electron distribution in the inner heliosphere include the field-aligned strahl, the suprathermal halo, the sunward deficit, and temperature anisotropy. These features are the result of a complex interplay between global expansion effects and local interactions between the particles and the electromagnetic fields. Global effects create, for example, the strahl via the mirror force in the decreasing magnetic field and the sunward deficit via reflections in the interplanetary electric field. Local wave-particle interactions such as instabilities change the shape of these features and thus the overall properties and moments of the electron distribution.

We discuss the science opportunities that the high-resolution data of Solar Orbiter's SWA/EAS sensor open up for unprecedented studies of the causes and effects of non-thermal electron distributions in the context of the expansion of the solar wind in the inner heliosphere. We focus, in particular, on the interplay between expansion effects and instabilities related to the electron strahl and the sunward deficit.

How to cite: Verscharen, D., Owen, C., Nicolaou, G., Coburn, J., Micera, A., and Innocenti, M. E.: Using non-thermal electron distributions to probe the inner heliosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15283, https://doi.org/10.5194/egusphere-egu23-15283, 2023.

Parker Solar Probe has detected abundant magnetic inversions and velocity spikes in the young solar wind, the origins of which are still highly debated. Numerous studies based on observational data and numerical simulations favor the causal correlation between interchange magnetic reconnection process and these velocity spikes. However, the specific process by which interchange magnetic reconnection leads to these structures is still inconclusive. Interchange reconnection should occur during the eruption of small bipoles in pre-existing open magnetic field regions such as coronal holes. This process is known to drive the formation of plumes and pseudo-streamer like structures and potentially mesoscale structures measured in the solar wind as well as velocity spikes. Using velocity measurements from Solar Orbiter we infer the magnetic origin of mesoscale structures and velocity spikes measured by Solar Orbiter, we find that the footpoints of the magnetic lines associated with these spikes are located at the boundary of a coronal hole observed by the Solar Dynamics Observatory (SDO), where the interchange magnetic reconnection is likely to occur. The imaging instruments aboard Solar Orbiter and SDO record one typical interchange magnetic reconnection event near the footpoints. With the high temporal/spatial resolution images obtained from multiple perspectives, we directly analyze the fluctuating motion of jet flow materials and explore the mechanism of fluctuation excitation during the interchange magnetic reconnection. We compare our observations with a 2.5D MHD simulation of interchange magnetic reconnection, we speculate that outward fluctuations may act as a kind of mediator between interchange magnetic reconnection and the formation process of velocity spikes/magnetic switchbacks.

How to cite: Hou, C., Rouillard, A., He, J., Gannouni, B., and Réville, V.: Possible Role of Fluctuation Excitation in the Formation of Alfvénic Fluctuations Originating from Interchange Magnetic Reconnection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15516, https://doi.org/10.5194/egusphere-egu23-15516, 2023.

With the launch of Solar Orbiter (SolO) together with STEREO A, and Wind it is again possible to study  multi-spacecraft Solar Energetic Particle (SEP) events within 1 AU. Over the timespan from July 2020 up to June 2022, we identify 44 events for which a significant increase of ∼100 keV electrons has been observed for at least two spacecraft. The maximum longitudinal separation of the two furthest spacecraft ranges from ∼17 to ∼217 degree. 

SEPs are expected to follow the Interplanetary Magnetic Field (IMF) which in zero-order approximation has the shape of Parker spirals. We investigate two different scenarios to identify the source of the widespread particle observation: (a) Particles are injected over a broad range of longitudes at the source surface without any perpendicular transport, hence by propagating along the IMF SEPs can be detected for distant observers. (b) Particles are injected over a narrow range of longitudes, but are distributed perpendicular to the nominal IMF by perpendicular diffusion. We discard events for which no unambiguously source location (e.g., flare) can be identified, or where an interplanetary coronal mass ejection is present. In order to investigate these scenarios a 2d  SEP transport model is utilized. The simulated data are compared to selected SEP observations. We developed a χ² minimization code in order to determine the most probable injection and transport parameters.

Here, we present our first modeling results for a selected number of multi-spacecraft SEP events involving SolO. Furthermore, we note that the multi-spacecraft event observation can be a result of a combination of case (a) and (b).

How to cite: Bruedern, M., Dresing, N., Heber, B., Kartavykh, Y., Kollhoff, A., Kühl, P., and Strauss, D. T.: Identifying the source of multi-spacecraft SEP events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15579, https://doi.org/10.5194/egusphere-egu23-15579, 2023.

Observations of plasma motions in the low corona are often limited to magnetic field lines originating in active regions, which are ideal for spatial domain enhancements across individual extreme ultraviolet (EUV) images to see loops, flares, and other bright activity contrasted against dim background features.

The quiet Sun is essentially all dim background features, which requires advanced image processing and ideal observation parameters to emphasize the temporal domain in order to visualize faint, fine-scale plasma flows. We utilize time-normalized optical flow (TNOF) on large sets of high cadence EUV data by reducing instrumental noise to a high degree and then emphasizing the minor brightness variations indicative of plasma motion. Maps of plasma flow paths are produced via optical flow tracking algorithms by the computer vision method of Lucas-Kanade and the underlying velocity field is estimated with line integral convolution.

To test the effectiveness of the TNOF approach, we have applied this method to an EUV case study of data from EUI 174 and AIA 171 on 29 March 2022. This date marked a near-perpendicular line of sight orientation between the two spacecraft, had similarly short observation intervals, and provided the opportunity to compare contrast enhanced plasma features off-limb with temporally enhanced on-disk plasma motion. 

In this case study, we generated movies and flow paths that show TNOF succeeds at qualitatively outlining plasma flow along magnetic field lines from both Solar Orbiter’s and SDO’s point of view which are in general agreement with potential field models. Additionally, detailed velocities of plasma motion within coronal loops, overall velocity trends, and a new quasi-magnetic flow trend within the quiet Sun are presented.

How to cite: Muro, G. and Morgan, H.: Time-normalized plasma flow mapping during the quadrature of SolO and SDO, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15710, https://doi.org/10.5194/egusphere-egu23-15710, 2023.

Magnetic reconnection is a fundamental process in astrophysical plasma, as it enables the dissipation of energy at kinetic scales. Detecting it in-situ is therefore key to further our understanding of energy conversion in space plasma. However, ion reconnection jets usually scale from seconds to minutes in-situ, and as such they can be quite tedious to find in the months or years of data provided by Wind, ACE, Helios, PSP and Solar Orbiter.

In this work, we use a new approach to identify automatically reconnection exhausts in-situ. The method strongly relies on the Walén relation and uses Bayesian inference as well as physical considerations to detect reconnection jets in-situ. Applying the detection algorithm to one month of Solar Orbiter data at 0.7 ~AU, we find an occurrence rate of 6.4~jets/day, which is significantly higher than in previous studies performed at 1~AU.  We repeat the analysis over the Solar Orbiter perihelion at 0.3 AU and show that the occurrence rate of magnetic reconnection tends to increase with radial distance.

We show that magnetic reconnection exhausts clearly cluster in the solar wind. We perform a statistical analysis, distinguishing between the exhausts associated with the heliospheric current sheet and turbulent reconnection. We find that the source and the degree of Alfvénicity of the solar wind might have an impact on magnetic reconnection occurrence.

How to cite: Fargette, N., Lavraud, B., Rouillard, A., Houdayer, P., Phan, T., Oieroset, M., Eastwood, J., Fedorov, A., Louarn, P., Owen, C., and Horbury, T.: Solar Orbiter reveals that reconnection jets cluster in the solar wind, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16072, https://doi.org/10.5194/egusphere-egu23-16072, 2023.

It is well known that flare-accelerated electrons can produce both hard X-ray (HXR) emission and Type-III radio bursts. The HXR emission is produced by the accelerated electrons propagating towards the chromosphere where they deposit their energy while Type-III radio bursts are produced by the accelerated electron beams traveling towards the outer solar atmosphere. Hence a temporal correlation between these two kinds of emission may imply a common origin of the accelerated electrons providing insight into the acceleration process, and allows us to connect electrons at the Sun to those in the heliosphere. On 2022-Nov-11 11:30 - 12:00 UT, the Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter observed a highly energetic flare event with an excellent time resolution of 0.5 s. Simultaneously there were observations of multiple coronal and interplanetary Type-III radio bursts from several instruments such as I-LOFAR, WIND/WAVES, NDA and ORFEES. I-LOFAR provides high-sensitivity imaging spectroscopy in the range of ~10-240 MHz with a time resolution of 1.31 ms and a frequency resolution of 195 kHz. We examine the temporal correlation between the X-ray and radio time series and discuss the relationship between the two and what it implies   about the origin of the electron populations producing these two kinds of radiation.

How to cite: Bhunia, S., Hayes, L., Maloney, S., and Gallagher, P.: Detailed look at the temporal correlation between hard X-ray flare and type III radio bursts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16350, https://doi.org/10.5194/egusphere-egu23-16350, 2023.

How to cite: Palmroth, M. and the Team: Magnetotail plasmoid eruption: Interplay of instabilities and reconnection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1094, https://doi.org/10.5194/egusphere-egu23-1094, 2023.

Turbulent magnetic reconnection was observed in the magnetotail and the magnetopause. In turbulent magnetic reconnection, the diffusion region is filled with a number of filamentary currents primarily carried by the electrons and some flux ropes. These dynamic filamentary currents constitute a kind of three-dimensional network in the diffusion region and lead the reconnection into turbulence. The electrons are trapped and sufficiently accelerated inside such a complicated current network.

According to the previous observations, magnetic reconnection generally displays a quasi-steady state in the solar wind, where the energy is dissipated via slow-mode shocks. It is elusive why the reconnection in the solar wind is quasi-steady. Here we present a direct observation of bursty and turbulent magnetic reconnection in the solar wind, with its associated exhausts bounded by a pair of slow-mode shocks. We infer that the plasma is more efficiently heated in the magnetic reconnection diffusion region than across the shocks and that the flow enhancement is much higher in the exhausts than in the area around the diffusion region. We detected 75 other, similar diffusion-region events in solar wind data between October 2017 and May 2019, suggesting that bursty reconnection in the solar wind is more common than previously thought and actively contributes to solar wind acceleration and heating.

How to cite: Wang, R., Li, X., Wang, S., Lu, Q., Lu, S., and Gonzalez, W.: Turbulent magnetic reconnection in the solar wind, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2060, https://doi.org/10.5194/egusphere-egu23-2060, 2023.

The heliosphere is a part of the Universe in which we can do in situ measurements of plasma dynamics under diverse conditions. The terrestrial magnetosphere is especially well accessible for studying universal plasma processes, in particular those associated with the conversion and flow of electromagnetic and plasma energy. To fully understand phenomena such as shocks, instabilities at plasma boundaries, and magnetic reconnection it is crucial to consider the coupling between physical processes at small and large scales. Planetary magnetospheric systems are not completely understood, because kinetic and global scales are rarely measured simultaneously. In most observations, the energy range and composition are not resolved for all important contributors.  The mentioned aspects are essential for an assessment of the magnetosphere-ionosphere-atmosphere-subsurface coupling and for the prediction of space weather. The influence of ionospheric charged particles on the magnetospheric dynamics will be used as an illustrative example. 

How to cite: Kronberg, E.: Open questions in heliophysics: terrestrial laboratory, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2179, https://doi.org/10.5194/egusphere-egu23-2179, 2023.

Earth’s radiation belts are a hazardous environment containing trapped charged particles. Radial diffusion is one of the major processes driving radiation belt physics, accounting for energisation, transport and loss of electrons in the outer belt. The outer radiation belt is highly variable in energy and location, resulting in behaviour which is difficult to model accurately.

Ensemble modelling is needed to characterise this variability. Ensembles can be constructed by varying physical parameters (capturing the uncertainty in our knowledge across many scales) and considering the spread of the final model outputs. However, it is unclear what proportion of the subsequent variability comes from physics versus the numerical methods used. We investigate the effect of varying initial conditions for typical radial diffusion coefficients.

We present two methods of establishing the timescale over which initial conditions affect the subsequent radial diffusion; time to monotonicity (the time taken for the particle distribution to reach a state where radial diffusion effects become uninteresting) and dimensional analysis. Both are needed to capture the processes we are interested in as well as the inherent timescales from diffusion. Our measures are often domain dependent, indicating that the choice of where we perform our radial diffusion simulations is significant.

How to cite: Bentley, S., Stout, J., Ratliff, D., Thomspon, R., and Watt, C.: Radial Diffusion Benchmarking: Initial Conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3258, https://doi.org/10.5194/egusphere-egu23-3258, 2023.

Comets hold the key to the understanding of our Solar System, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma, and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the Solar System, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. The Rosetta mission and previous fast flybys of comets have together made many new discoveries, but the most important breakthroughs in the understanding of cometary plasmas are yet to come. The Comet Interceptor mission will provide a sample of multi-point measurements at a comet, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the Solar System. We will review the present-day knowledge of cometary plasmas, discuss the many questions that remain unanswered, and outline a multi-spacecraft European Space Agency mission to accompany a comet that will answer these questions by combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems.

How to cite: Goetz, C. and the Cometary Plasma Science White Paper Team: Cometary Plasma Science - Open questions and implications for heliophysics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3517, https://doi.org/10.5194/egusphere-egu23-3517, 2023.

Stella is a proposed European contribution to NASA’s Interstellar Probe (ISP), a large-strategic mission candidate. ESA’s call for M-class mission proposals was the best and only currently available option for the European science community to contribute to the astronomically constrained ISP launch window in 2036 – 2037. Traveling with a speed of ~ 7.0 au/year ISP would reach 350 au during its nominal 50-year life-time. The proposed Stella contribution to ISP includes two core and two optional elements for the full complement:

• Core: Provision of European scientific instruments;

• Core: Provision of the European ISP communication system including the spacecraft’s 5-m high gain antenna;

• Full complement: ESA deep space communication facility: an extension of ESA’s DSA with a new antenna array;

• Full complement: Contribution to ISP operations to increase drastically the ISP and European payloads science return.

How to cite: Wimmer-Schweingruber, R. F., André, N., Barabash, S., Brandt, P. C., Horbury, T. S., Iess, L., Lavraud, B., McNutt, Jr., R. L., Provornikova, E. A., Quémerais, E., Wicks, R., Wieser, M., and Wurz, P.: STELLA—Potential European  contributions to a NASA-led interstellar probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4065, https://doi.org/10.5194/egusphere-egu23-4065, 2023.

Radial diffusion in planetary radiation belts is a dominant transport mechanism resulting in the energisation and loss processes of charged particles by ultra-low frequency (ULF) fluctuations in the Pc4-Pc5 range. The theoretical framework upon which radial diffusion coefficients have been analytically derived in the past 60 years belongs to various types of quasi-linear theories. In quasi-linear theories, the evolution equation for the distribution function experiencing radial diffusion is only valid on slow timescales longer than the characteristic period of the ULF waves and the azimuthal drift period of the particles, ranging from tens of minutes to a few hours for electrons with energies between tens of keV to several hundreds of keV. Therefore, radiation belts’ dynamical processes occurring on fast timescales comparable to ULF wave periods or azimuthal drift periods, such as fast magnetopause losses localised in magnetic local time (MLT), cannot self-consistently be quantified in terms of radial diffusion models. In this communication, we present a new theoretical framework based on drift kinetic (Hazeltine, 1973) to distinguish between the fast and slow response of energetic electrons to ULF waves. We conclude our talk with two examples to demonstrate the benefits of the drift kinetics approach: 1) fast electron losses due to MLT localised compression of the magnetopause, and 2) non-diffusive acceleration associated with symmetric ULF fluctuation.  

How to cite: Osmane, A.: A new theoretical framework to model radial transport of energetic particles by ULF waves in the Earth's magnetosphere., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5242, https://doi.org/10.5194/egusphere-egu23-5242, 2023.

The majority of the atmospheres of solar system bodies are composed of neutral gas, and hence their upper atmosphere are always partially ionized by the solar UV and collisions, allowing a complex nonlinear interaction with interplanetary plasma.  Thus, ion-neutral and electron-neutral interaction plays a key role in this transition regions (ionosphere for planets and moons). However, our current understanding of plasma-neutral gas interactions is very limited due to lack of observations with proper instrumentation and to the difficulty in making laboratory experiments (almost impossible to reproduce the ionosphere with low energy plasma).  Particularly the effect of small amount of neutral species in space above the exobase and the effects of electric charges on neutrals have been underestimated.  

To advance our knowledge of these basic but still poorly understood interactions between plasma and neutral gas at key regions of energy, momentum, and mass exchange between the space and the atmosphere, we evaluate what kind of measurement package is needed for different solar system objects in a cost-effective manner.  We particularly focus on understanding the re-distribution of externally provided energy to the composing species through this interaction.  

The presentation is based on a white paper submitted to ESA's Voyage 2050 (Experimental Astronomy, 2022), and related mission proposals to space agencies.  Here we skip the chemical aspect that is also mentioned in the white paper.

Reference: https://doi.org/10.1007/s10686-022-09846-9

How to cite: Yamauchi, M., De Keyser, J., Parks, G., Oyama, S., Wurz, P., Abe, T., Beth, A., Dunlop, M., Henri, P., Kucharek, H., Marghitu, O., Nicolaou, G., Shimoyama, M., Saur, J., Taguchi, S., Tsuda, T., and Tsurutani, B.: Plasma-neutral gas interactions in various space environments beyond simplified approximations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5715, https://doi.org/10.5194/egusphere-egu23-5715, 2023.

The lower thermosphere-ionosphere (LTI) is a key transition region between the Earth’s neutral atmosphere and plasma-dominated space. Interactions between ions and neutrals maximize within the LTI and in particular at altitudes from 100 to 200 km, which is the least visited region of the near-Earth environment due to enhanced atmospheric drag. The lack of in situ co-temporal and co-spatial measurements of all relevant parameters and their elusiveness to most remote-sensing methods means that the complex interactions between neutral and charged constituents in the LTI remain poorly characterized to this date. This lack of measurements, together with the ambiguity in the quantification of key processes in the 100 to 200 km altitude range, affect current modeling efforts to expand atmospheric models upward to include the LTI and limit current space weather prediction capabilities. In this talk, fundamental science themes in ionosphere-thermosphere physics and related societal and operational needs are outlined; past proposed implementation schemes to sample this transition region are reviewed; and recent efforts by ESA and NASA to highlight outstanding science questions in the LTI and the need for in situ measurements to address them are presented.

How to cite: Sarris, T. and the co-authors of the white paper for the decadal survey for solar and space physics 2024-2033: Plasma-Neutral Interactions in the Lower Thermosphere-Ionosphere: The need for in situ measurements to address outstanding questions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5939, https://doi.org/10.5194/egusphere-egu23-5939, 2023.

 The global structure of the Sun’s extended corona is governed by the physical processes which represent some of the biggest outstanding questions in heliophysics. These include the nature of coronal heating and solar wind acceleration. NASA’s Parker Solar Probe (PSP) offers unique new opportunities to probe this structure directly through its unprecedented orbit which takes it closer to the Sun than any prior spacecraft. As of Spring 2023, PSP has achieved perihelia of 13.3 Rs, but will continue to dive deeper to an eventual closest approach of 9.8Rs at the end of 2024. Already PSP is starting to offer tantalizing glimpses into the sub-alfvenic corona. The most recent orbits exhibit hints of an imminent global plasma regime change on multiple fronts: As well as unambiguous crossings of the Alfven critical surface, PSP sees significant solar wind deceleration, possible global magnetic field reorganization, and proton core temperatures hot enough to be comparable to isothermal solar wind models. In this talk, we will discuss how these exciting initial measurements may become decisive constraints in the latter orbits of the PSP mission. We trace the implications of making such direct measurements of the corona-solar wind transition to the science questions of coronal heating and solar wind acceleration.

How to cite: Badman, S., Rivera, Y., Bale, S., and Stevens, M.: Global coronal structure and possible new insights in the upcoming perihelia of Parker Solar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6626, https://doi.org/10.5194/egusphere-egu23-6626, 2023.

Exploration of the Moon provides opportunities to investigate the deep space environment upstream of the geospace and the terrestrial magnetosphere and associated space weather phenomena. Moreover, the Moon interaction with the solar wind adds novel, interdisciplinary aspects to fundamental space research: a complex coupling between the solar wind/magnetospheric plasma – energetic particles – exosphere – dust – solid-surface – mini-magnetosphere. As the Moon is the next step in space exploration, characterizing the environment provides vital support to this endeavor. We note that investigations in this area of science are invaluable in providing a characterization of the environment for the needs of human exploration. On the other hand,  the lunar environment is fragile against human activities. For example, the total mass of the lunar atmosphere is of the order of 10 tons. Therefore, the environment will change drastically once human activity starts on the lunar surface. It is significantly essential to characterize the environment before the fragile lunar atmosphere is “contaminated” by human activities at the surface.
With these aspects as a background, we formed an ESA topical team to formulate scientific questions in space plasma physics that can be uniquely investigated on or near the lunar surface. We also derived the required measurements, which can be addressed by lunar missions in the short and long term, including the EL3 (European Logistic Lunar Lander) mission. This presentation introduces the background scientific context and describes the derived scientific concepts. 

How to cite: Futaana, Y. and the ESA Topical Team : Physics Of Plasma-Surface-Exosphere-Dust Coupling At The Lunar Surface For Future Exploration Programmes: Physics of plasma–surface–exosphere–dust coupling at the lunar surface for future exploration programmes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6791, https://doi.org/10.5194/egusphere-egu23-6791, 2023.

Space plasmas are composed of charged particles that play a key role in electromagnetic dynamics. However, to date, there has been no direct measurement of the distribution of such charges in space. In this study, three schemes for measuring charge densities in space are presented. The first scheme is based on electric field measurements by multiple spacecraft. This method is applied to deduce the charge density distribution within Earth’s magnetopause boundary layer using Magnetospheric MultiScale constellation (MMS) 4-point measurements, and indicates the existence of a charge separation there. The second and third schemes proposed are both based on electric potential measurements from multiple electric probes. The second scheme, which requires 10 or more electric potential probes, can yield the net charge density to first-order accuracy, while the third scheme, which makes use of seven to eight specifically distributed probes, can give the net charge density with second-order accuracy. The feasibility, reliability, and accuracy of these three schemes are successfully verified for a charged-ball model. These charge density measurement schemes could potentially be applied in both space exploration and ground-based laboratory experiments.

How to cite: Shen, C.: Measuring the Net Charge Density of Space Plasmas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7030, https://doi.org/10.5194/egusphere-egu23-7030, 2023.

How does solar wind energy flow through the Earth’s magnetosphere, how is it converted and distributed? This are the questions we want to address. We need to understand how geomagnetic storms and substorms start and grow, not just as a matter of scientific curiosity, but to address a clear and pressing practical problem: space weather, which can influence the performance and reliability of our technological systems, in space and on the ground, and can endanger human life and health.

Much knowledge has already been acquired over the past decades, particularly by making use of multiple spacecraft measuring conditions in situ, but the infant stage of space weather forecasting demonstrates that we still have a vast amount of learning to do. A novel global approach is now being taken by a number of space imaging missions which are under development and the first tantalising results of their exploration will be available in the next decade. In a White Paper, submitted to ESA in response to the Voyage 2050 Call, we propose the next step in the quest for a complete understanding of how the Sun controls the Earth’s plasma environment: a tomographic imaging approach comprising two spacecraft in highly inclined polar orbits, enabling global imaging of magnetopause and cusps in soft X-rays, of auroral regions in FUV, of plasmasphere and ring current in EUV and ENA (Energetic Neutral Atoms), alongside in situ measurements. Such a mission, encompassing the variety of physical processes determining the conditions of geospace, will be crucial on the way to achieving scientific closure on the question of solar-terrestrial interactions.

The White Paper was published on 16 August 2021 (G. Branduardi-Raymont et al., Experimental Astronomy, https://doi.org/10.1007/s10686-021-09784-y) and full co-author details are at the end of the article.

How to cite: Branduardi-Raymont, G.: Exploring solar-terrestrial interactions via multiple imaging observers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7436, https://doi.org/10.5194/egusphere-egu23-7436, 2023.

Toward the inner Heliospheric system science exploration in the late 2020s, ISAS/JAXA is currently operating the Arase, BepiColombo/Mio, Hinode, and Akatsuki satellites, and Solar-C EUVST is scheduled for launch in the near future. These missions will be linked together with other satellite missions such as Solar-Orbiter, Solar Parker Probe, Cluster, THEMIS, MMS etc. to realize exploration of the inner Heliosphere with unprecedented scale.

In the early 2030s, Japanese Solar Terrestrial Physics group is considering the FACTORS formation-flight satellite mission in order to reveal the energy coupling mechanisms and mass transport between the space and Earth’s atmosphere. In the late 2030s, another formation-flight magnetospheric satellite mission the science target of which includes understanding the cross-scale / cross-region coupling is also under consideration hopefully on orbit at the same time with European future mission Plasma Observatory. These future missions will closely collaborate with NASA’s future GDC and Magnetospheric Constellation missions.

The future Heliospheric system science exploration will be conducted by multiple satellite missions further expanding their observation area while improving the quality of each individual satellite mission. Japanese Solar Terrestrial Physics group will conduct in-situ observation of space plasmas with MMX (Martian Moons Exploration) and MIM(Mars Ice Mapper) in the Martian system and with JUICE (Jupiter Icy Moons Explorer) in the Jovian system. Collaboration between Japanese Solar Physics and Solar Terrestrial Physics groups for considering the future out-of-ecliptic-plane mission is also about to start.

In order to realize the future Heliospheric system science exploration, significant technological development is mandatory. Current status of the technological development in Japan for enabling the future Heliospheric system science exploration will also be presented.

How to cite: Saito, Y., Miyoshi, Y., Seki, K., and Imada, S.: Future Heliospheric System Science Exploration in Japan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8410, https://doi.org/10.5194/egusphere-egu23-8410, 2023.

Coronal mass ejections (CMEs) contribute closed magnetic flux to the heliosphere while they are connected at both ends to the Sun and play a key role in adding magnetic flux to the heliosphere. Here, we discuss an outstanding question in heliophysics: how the type of magnetic reconnection that opens CME field lines in the inner heliosphere, i.e. interchange (IC) reconnection (below the Alfvén surface) and/or interplanetary (IP) reconnection (above the Alfvén surface), determines the length of time CMEs contribute to the heliospheric flux budget. Although IP reconnection does not alter the total amount of magnetic flux in the heliosphere, it matters in this context because it prevents the efficient opening of CME closed magnetic flux through IC reconnection, thereby prolonging the length of time that CMEs contribute closed magnetic flux to the heliosphere. We suggest that there is a varying timescale of contribution of individual CMEs to the heliospheric flux budget, with some CMEs contributing for considerably longer than others, depending on their interactions in IP space (i.e., depending on the fraction of the CME magnetic field lines opened up through IP reconnection vs. IC reconnection, or both). Such a distinction has not been taken into account in past studies that estimate the CME flux opening timescale. We outline key criteria to aid in distinguishing IC reconnection from IP reconnection based on in situ spacecraft data and highlight these through two example events. Studying the manner in which CMEs reconnect and open in the inner heliosphere has implications for a broad range of solar and heliospheric physics research areas and yields important insights not only into CMEs' role in the heliospheric flux budget but also the evolution of CME complexity, connectivity, and topology.

How to cite: Winslow, R., Scolini, C., Lugaz, N., Schwadron, N., and Galvin, A.: On the Contribution of Coronal Mass Ejections to the Heliospheric Magnetic Flux Budget on Different Time Scales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8879, https://doi.org/10.5194/egusphere-egu23-8879, 2023.

The Earth's Magnetospheric System is the complex and highly dynamic environment in near-Earth space where plasma gets actively energized and transport of large amounts of energy occurs, due to the interaction of the solar wind with the Earth's magnetic field. Understanding plasma energization and energy transport is an open challenge of space plasma physics, with important implications for space weather science as well as for the understanding of distant astrophysical plasmas. Plasma energization and energy transport are related to fundamental processes such as shocks, magnetic reconnection, turbulence and waves, plasma jets and instabilities, which are at the core of the current space plasma physics research. ESA/Cluster and NASA/MMS four-point constellations, as well as the large-scale multipoint mission NASA/THEMIS, have greatly improved over the last two decades our understanding of plasma processes at individual scales compared to earlier single-point measurements. Despite the large amount of available observations, we still do not fully understand the physical mechanisms which give rise to plasma energization and energy transport. The reason is that the fundamental physical processes governing plasma energization and energy transport operate across multiple scales ranging from the large fluid to the smaller kinetic scales. Here we present the Plasma Observatory (PO) multiscale mission concept which is tailored to study plasma energization and energy transport within the Earth's Magnetospheric System. PO baseline is comprised of one mothercraft (MSC) and six identical smallsat daughtercraft (DSC) in an HEO 8 RE X 18 RE orbit, covering all the key regions of the Magnetospheric System where strong energization and transport occur: the foreshock, bow shock, magnetosheath, magnetopause, magnetotail current sheet, and the transition region. MSC payload provides a complete characterization of electromagnetic fields and plasma particles in a single point with time resolution sufficient to resolve kinetic physics at sub-ion scales. The DSCs have identical payload which is much simpler than on the MSC, yet giving a full characterization of the plasma at the ion and fluid scales. Going beyond Cluster, THEMIS and MMS, PO will permit us to resolve for the first time the coupling between ion and fluid scales as well as the non-planarity and non-stationarity of plasma structures at those scales.  PO is one of the five ESA M7 candidates to be launched around 2037 and is currently undergoing a competitive Phase 0 at ESA for further downselection to Phase A at the end of 2023.

How to cite: Marcucci, M. F., Retinò, A., Dunlop, M., Forsyth, C., Khotyaintsev, Y., Le Contel, O., Mann, I., Nakamura, R., Palmroth, M., Plaschke, F., Soucek, J., Yamauchi, M., Vaivads, A., and Valentini, F. and the Plasma Observatory Team: Plasma Observatory ESA M7 candidate mission: unveiling plasma energization and energy transport through multiscale observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9043, https://doi.org/10.5194/egusphere-egu23-9043, 2023.

Heliophysics, the science of understanding the Sun and its interaction with the Earth and the solar system, has a large and active international community, with significant expertise and heritage in the European Space Agency and Europe. Several ESA directorates have activities directly connected with this topic, including ongoing and/ or planned missions and instrumentation, comprising a ESA Heliophysics observatory or more musically, a Heliophysics Orchestra. More specifically in ESA: The Directorate of Science with mission such as Ulysses, SOHO, Cluster, Solar Orbiter, SMILE etc, as well as hosting the Heliophysics archive; The Directorate of Earth Observation with Swarm and other Earth Explorer missions, as well as the ongoing ESA-NASA Lower Thermosphere-Ionosphere Science Working Group (EN-LoTIS-WG); The Directorate of Operations with the Vigil mission, the Distributed Space Weather Sensor System (D3S) and the Space Weather Service Network; The Directorate of Human and Robotic Exploration with many ISS and LOP-Gateway payloads and the Directorate of Technology, Engineering Quality with expertise in developing instrumentation and models for measuring and simulating environments throughout the heliosphere.

An ESA Heliophysics Working group has been appointed by several ESA Directors, under the direction of the ESA Director General, to work on optimizing synergies across directorates, and to act as a focus for discussion, inside ESA, of the scientific interests of the Heliophysics community, including the European ground-based community and data archiving activities. 

How to cite: Taylor, M., Jiggins, P., Luntama, J.-P., Orr, A., and Strømme, A.: The ESA Heliophysics Working Group: building cross-discipline bridges to better serve the European Heliophysics  community, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9223, https://doi.org/10.5194/egusphere-egu23-9223, 2023.

Heliophysics is the study of the Sun and its effects throughout the solar system. It covers an incredible range of scales, from plasma physics at the electron scale to the boundary that separates our solar system from interstellar space. It also includes a diverse array of sub disciplines and expertise, with measurements spanning in situ particles and fields from the ionosphere out to the Sun’s corona, to remote sensing of the Sun, heliosphere, and near-Earth environment at multiple wavelengths and in energetic neutral atom observations. Many of the biggest unanswered science questions that remain across Heliophysics center around the interconnectivity of the different physical systems that comprise the Heliosphere, and the role of mesoscale dynamics in modulating, regulating, and controlling that interconnected behavior. These are complex, yet ultimately fundamental questions of how the Sun-Heliosphere and Geospace interact, and answers are needed to more accurately predict and model space weather impacts on and around Earth, the moon, and Mars. To answer these long-standing questions on the Sun-Heliosphere and Geospace as system-of-systems, we believe that Heliophysics requires a coordinated, deliberate, worldwide scientific effort. We suggest that the worldwide Heliophysics discipline should embark on a grand program to study these system-of-systems holistically, with coordinated, multipoint measurements, with particular emphasis on resolving mesoscale dynamics, and a whole-of-science approach that includes ground-based measurements and advanced numerical modeling. Without such a unified, next generation ISTP-type program, these questions will remain largely unanswered. In this paper we lay out the case for such an approach, and discuss how the ITM community is using the upcoming NASA GDC mission as a cornerstone to develop the ITM Great Observatory, a grass-roots, holistic approach modeled after ISTP to study the ITM system.

How to cite: Kepko, E. and the COSPAR Task Group on Establishing an International Geospace Systems Program: ISTPNext and the ITM Great Observatory: The need for international coordination in Heliophysics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9239, https://doi.org/10.5194/egusphere-egu23-9239, 2023.

Our solar system has evolved through accretion of dust and gas as the Sun and its protective magnetic bubble – “the heliosphere” - have plowed through interstellar space on its journey through the galaxy. Over the course of its evolution, the solar system has encountered dramatically different interstellar properties resulting in a severely compressed heliosphere with periods of full exposures of interstellar gas, plasma, dust and galactic cosmic rays (GCRs) that all have helped shaped the system we live in today. Our current knowledge lacks the direct measurements necessary to understand how our star upholds its vast heliosphere and its potentially game-changing role in the evolution of our galactic home.

Voyager 1 and 2 are now in the Very Local Interstellar Medium (VLISM), where they are expected to operate until the mid-2030’s having uncovered many unexpected discoveries and mysteries. After its paradigm-shifting discoveries at Pluto and Arrokoth, New Horizons is currently the only spacecraft in the outer heliosphere and is following the same heliospheric longitude as Voyager 2, but in the ecliptic plane – a trajectory that intersects the IBEX ribbon. It is projected to operate across the heliospheric termination shock and possible the heliopause with new measurements that will shed light on many of the mysteries of our heliosphere. Now passing 55 au, New Horizons is uniquely positioned to investigate the evolution of the solar wind, energetic particles, GCRs, and, in particular interstellar Pick-Up Ions (PUIs) that Voyager was not equipped to measure, to help constrain the structure and dynamics of the heliosphere. Observations of GCRs offers an opportunity to understand how these scatter strongly in the wavy structure of the “ballerina skirt” of the solar magnetic field leading to the strong modulation as part of the overall heliospheric shielding.

As New Horizons continues to travel outward, dust measurements may reveal an interstellar component that will provide the strongest constraint to date on how interstellar dust grains interact with the heliosphere. Now beyond the infrared and UV haze of the circumsolar dust and hydrogen gas, the Alice UV camera holds promise to search for signatures of the hydrogen wall and perhaps even signatures of our neighboring interstellar clouds.

New Horizons continues to break new ground in understanding the formation of our solar system by revealing the properties of multiple distant Kuiper Belt Objects and provide critical constraints on the structure of the Sun’s enormous dust disk. Because of its distant position, New Horizons is also providing the unprecedented estimates of the cosmic background.

In this presentation we provide an overview of New Horizons’ heliophysics observations in the context of the exploration by Voyager, IBEX, and IMAP. We conclude by providing a status of the future Interstellar Probe mission concept that is now under consideration in the Solar and Space Physics Decadal Survey.

How to cite: Brandt, P., Stern, A., Spilker, L., Elliott, H., Hill, M., Kollmann, P., McNutt, R., Mostafavi, P., McComas, D., Gladstone, R., Horanyi, M., Poppe, A., Provornikova, E., Linsky, J., Redfield, S., Lauer, T., Singer, K., Spencer, J., Verbiscer, A., and Opher, M.: Our Heliosphere in the Very Local Interstellar Medium: Exploration by New Horizons, Voyager, IBEX, IMAP and a Future Interstellar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9872, https://doi.org/10.5194/egusphere-egu23-9872, 2023.

Nonthermal energetic pickup ions (PUIs), created in the heliosphere by charge exchange between solar wind ions and interstellar neutral atoms, play an essential role in understanding solar wind evolution in the outer heliosphere and the structure and dynamics of the global heliosphere. New Horizons spacecraft, launched in 2006, is now located at about 55 au from the Sun, exploring the outer heliosphere, and is the only spacecraft equipped with proper instruments to measure nonthermal energetic pickup ions (PUIs) in the outer heliosphere for the first time. Its observations showed that energetic PUIs dominate the internal pressure of the outer heliosphere, with PUI pressures larger than the thermal solar wind and magnetic pressures outside ~ 20 au. At these distances, PUIs contribute substantially to heating and slowing down the solar wind. Moreover, New Horizons observations showed that PUIs mediate shock waves in the outer heliosphere. Here, we give an overview of the energetic particles in the outer heliosphere and their effect on shocks. We present the in situ observations of the hydrogen and Helium PUIs made by New Horizons' SWAP and PEPSSI instruments. Finally, we present some of the most important open questions related to the outer heliosphere that future studies and space missions should address.

How to cite: Mostafavi, P., Hill, M., Kollmann, P., Brandt, P., McNutt, R., Stern, A., Shrestha, B., Bagenal, F., Singer, K., Verbiscer, A., and Spencer, J.: Energetic Particles in the Outer Heliosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10279, https://doi.org/10.5194/egusphere-egu23-10279, 2023.

In the 2020s we are entering a golden age of inner heliosphere science. International Mercury exploration mission BepiColombo was launched in 2018 and will arrive at Mercury in 2025. During the interplanetary cruise phase, BepiColombo will range from 1.2 AU to 0.3 AU, and will stay in the inner heliosphere for long time. BepiColombo started its science observations during the interplanetary cruise phase in 2020. The initial results showed its enough performance to observe solar wind electrons, IMF, and solar energetic particles (SEPs) even in the composite spacecraft configuration. Especially in 2021 two spacecraft of BepiColombo, Mercury Planetary Orbiter (MPO) and Mercury Magnetosphere Orbiter (Mio), successfully detected many SEP events. BepiColombo can contribute to leading and expanding the heliospheric system science. In addition to BepiColombo, NASA’s Parker Solar Probe and ESA’s Solar Orbiter are also exploring the inner heliosphere. Coordinated observations between these multi spacecraft have been planned and performed. In March 2021, we also coordinated a joint observation campaign of the solar corona and solar wind with BepiColombo, Akatsuki, and Hinode. These coordinated observations/analysis with multi spacecraft, ground-based observations, and numerical simulations can give us great opportunities to address outstanding questions in heliophysics. Here we Here we present the overview and updated status of BepiColombo and the coordinated science observations.

How to cite: Murakami, G. and Benkhoff, J.: Coordinated observations for inner heliospheric science: contribution by the BepiColombo mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11768, https://doi.org/10.5194/egusphere-egu23-11768, 2023.

A major part of the transport of the magnetic flux and energy in the midtail and the near-Earth tail region is accomplished by local fast plasma jets, called bursty bulk flows (BBF) or flow bursts.  The interaction between BBF and ambient field plays an important role in the complex chain of solar wind-magnetosphere-ionosphere coupling processes. Furthermore, near-Earth flow braking/bouncing processes and associated magnetic and pressure disturbances in the transition region of the magnetic field configuration from tail-like to dipolar field  lead to complex localized current sheet restructuring. Associated energetic particle injection further effects the inner magnetosphere bringing in the source population of the plasma waves that cause electron accelerations as well as seed populations of the radiation belts.

In this presentation we stress the importance of observations of BBF and dipolarization by covering extensive region, both near the equator and off-equator simultaneously, for understanding the energy transport processes by including both the field-aligned and perpendicular evolution of the flux tube.  By showing several examples of observations with fortuitous multi-spacecraft configuration, 3D nature of the interaction between BBF and ambient plasma will be discussed. 

How to cite: Nakamura, R., Miyoshi, Y., and Panov, E.: 3D evolution of localized plasma flow and its interaction with ambient field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11849, https://doi.org/10.5194/egusphere-egu23-11849, 2023.

Citizen science provides a way to analyze large and complex data sets, complementary to contemporary tools such as machine learning. Indeed, while trained algorithms excel in the task they are trained for, humans can spot outliers and make serendipitous discoveries. With recent and new instruments, we are able to observe the Sun and the heliosphere at high cadence and high resolution, providing large amounts of data, revealing complexity in the observed features, and leading to the discovery of new features on small scales. We will present how citizen science, while still under-utilized in solar and heliospheric physics, is particularly adapted to explore, and analyze solar data sets. The “Solar Jet Hunter”, a citizen science project launched one year ago to build a catalog of coronal jets, will be presented as an example, and other science cases for which citizen science is the most adequate tool will be highlighted. Finally, the opportunities raised by citizen science to create strong relationships between academia and society will be discussed.

How to cite: Musset, S., Glesener, L., Sankar, R., Fortson, L., Jol, P., Lasko, K., Zhang, Y., Panesar, N., Fleishman, G., Jeunon, M., Hurlburt, N., and Zheng, Y.: Citizen science and the exploration of solar data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12289, https://doi.org/10.5194/egusphere-egu23-12289, 2023.

The “Mars Magnetosphere ATmosphere Ionosphere and Space-weather SciencE (M-MATISSE)” mission is an ESA Medium class (M7) candidate currently in Phase 0 study by ESA. M-MATISSE’s main scientific goal is to unravel the complex and dynamic couplings of the Martian magnetosphere, ionosphere and thermosphere (MIT coupling) with relation to the Solar Wind (i.e. space weather) and the lower atmosphere. It will provide the first global characterisation of the dynamics of the Martian system at all altitudes, to understand how the atmosphere dissipates the incoming energy from the solar wind, including radiation, as well as how different surface processes are affected by Space Weather activity.

M-MATISSE consists of two orbiters with focused, tailored, high-heritage payloads to observe the plasma environment from the surface to space through coordinated simultaneous observations. It will utilize a unique 3-vantage point observational perspective, with the combination of in-situ measurements by both orbiters and remote observations of the lower atmosphere and ionosphere by radio crosstalk between them.

M-MATISSE is the product of a large organized and experienced international consortium. It has the unique capability to track solar perturbations from the Solar Wind down to the surface, being the first mission fully dedicated to understand planetary space weather at Mars. It will revolutionize our understanding and ability to forecast potential global hazard situations at Mars, an essential precursor to any future robotic & human exploration.

How to cite: Sanchez-Cano, B. and the the M-MATISSE team: The M-MATISSE mission: Mars Magnetosphere ATmosphere Ionosphere and Space weather SciencEAn ESA Medium class (M7) candidate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13687, https://doi.org/10.5194/egusphere-egu23-13687, 2023.

ESA F-Class missions offer a new opportunity to do space science with smaller, cheaper spacecraft. The mission format presents a tough challenge for plasma physics missions, can we make simple, small and cost-effective spacecraft for a topic that will make breakthrough discoveries? This presentation will discuss the past two proposals of the Debye mission, the lessons learned and the challenges ahead to make a similar mission feasible. Debye addresses a grand-challenge problem at the forefront of physics: to understand how energy is transported and transformed in plasmas. The smallest characteristic scales, at which electron dynamics determines the behaviour of energy, are the next frontier in space and astrophysical plasma research. Debye will be the first electron-astrophysics mission. Electron-kinetic processes operate at very small scales (< 10 km) but define the behaviour of the plasma at system-size scales. Debye will use the solar wind as a natural plasma laboratory to measure these electron-scale processes. Understanding the heating, acceleration, thermalisation, and heat flux of electrons is fundamental to our understanding of the dynamics and thermodynamics of plasmas throughout the Universe and thus to the entire field of astrophysics. Debye will answer the fundamental science question "How are electrons heated in astrophysical plasmas?" The mission will make the highest-resolution measurements of electrons ever made in space in terms of energy, angle, time, and space, coupled with two-point high-cadence field measurements to identify the plasma fluctuations responsible for electron energisation. This mission concept will provide ground-breaking and transformative physics results since the combination of rapid particle and field measurements over distances of less than 10 km is completely unprecedented. We believe Debye is a fast, feasible, and focussed mission, tailored to achieve these science objectives, but there are some technical challenges that are assessed to be problematic, how can we address data transmission, formation flying, the cost of multi-item payloads and multi-spacecraft missions?

How to cite: Wicks, R. and Verscharen, D.: Electron-astrophysics in the solar wind: plasma physics at F-Class, lessons learned and things to do., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13772, https://doi.org/10.5194/egusphere-egu23-13772, 2023.

The PSP observation of a long-lived sub-Alfvénic solar wind, along with its magnetic-dominant character, marks a milestone that a human spacecraft has entered the solar corona for the first time (Kasper et al. 2021 PRL). In fact, sub-Alfvénic solar wind streams have also been observed multiple times near the earth by WIND spacecraft. What are the difference and possible connections between the sub-Alfvénic streams very close to the sun and the sub-Alfvénic streams 1 au from the sun? What process generates and sustains the near-earth sub-Alfvénic streams as they propagate outwards? Why the yearly occurrence frequency of them strongly correlates with solar activity? We study several sub-Alfvénic streams, which can be categorized into two groups: sub-Alfvénic background solar wind and sub-Alfvénic ICMEs. In-situ observations, remote observations, and connecting tools are used in our study. We find the sub-Alfvénic background streams are magnetic enhancements embedded in rarefactions. Their origin can be the boundary of the expanding coronal holes and shrinking active regions. A sub-Alfvénic ICME is generally a low-density part of the whole ICME, whose solar origin tends to be elusive in the coronagraph but still geomagnetically effective because of the ICME magnetic field.

How to cite: Lin, R., He, J., and Hou, C.: Sub-Alfvénic solar wind streams near the earth: characteristics and their origin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14278, https://doi.org/10.5194/egusphere-egu23-14278, 2023.

Cool plasmas (≈ 10⁴ K) embedded in a larger, much hotter (>10⁶ K) medium are ubiquitous in different astrophysical systems such as solar & stellar coronae, the circumgalactic (CGM), interstellar (ISM) and intra-cluster (ICM) media. The role of these multiphase plasmas has been highlighted in mass-energy cycles at all such scales, from thermal non-equilibrium (TNE) cycles in the solar atmosphere to precipitation-regulated feedback cycles that drive star and galaxy formation. The properties of the cool plasmas across these multiple scales is strikingly similar, intimately linked to the yet unclear but fundamental mechanisms of coronal and ICM heating and instabilities of thermal or other nature. The solar corona constitutes a formidable and unique astrophysics laboratory where we can spatially and temporally resolve the physics of such multiphase plasma. The multi-faceted and measured response of the solar atmosphere to the heating is exemplified by TNE cycles that manifest through EUV intensity pulsations and through the generation of cool coronal rain and prominences whose mysterious properties are like that of multiphase filamentary structure in the ISM and ICM or to molecular loops in the Galactic centre. Coronal rain also occurs across a wide energetic scale extending to flares, whose features seem recurrent in active stars but remains poorly investigated due to lack of multi-temperature coverage at appropriate resolution. The formation and stability-loss of prominences is of major importance to space weather and their ‘slingshot’ counterparts provide unique diagnostic capabilities to the wind mass-loss rate. These exciting new cross-disciplinary possibilities are part of a Heliophysics Decadal Survey white paper and call for a high-resolution multi-wavelength imaging and spectroscopic solar instrument able to capture the multithermal, dynamic and pervasive nature of the multiphase plasma in the hot solar corona.

How to cite: Antolin, P. and Froment, C.: Cool Multiphase Plasma in Hot Environments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15055, https://doi.org/10.5194/egusphere-egu23-15055, 2023.

CSIRO, Australia's national science agency, operates a number of world-class radio astronomy observatories that are collectively known as the Australia Telescope National Facility (ATNF). The facility offers a powerful view of the southern hemisphere radio spectrum and supports world-leading research by Australian and international astronomers. Decades after the Culgoora Radioheliograph made fundamental discoveries about solar radio bursts, a new generation of radio telescopes in Australia are providing unique measurement capabilities to address outstanding questions in Heliophysics. Inyarrimanha Ilgari Bundara (“Sharing the Sky and Stars”), the CSIRO Murchison Radio-astronomy Observatory in Western Australia, is home to the Murchison Widefield Array (operated by a consortium led by Curtin University), the Australian Square Kilometre Array Pathfinder (ASKAP), and the future home of the Square Kilometre Array (SKA)-Low Telescope. Interplanetary scintillation (IPS) measurements by these radio telescope arrays will provide important observational constraints of the solar wind and interplanetary coronal mass ejections (ICMEs). This is enabled by simultaneous detections of a high density of scintillating sources over a wide field of view. Complementarily, Parkes Radio Telescope observations towards pulsars may provide density and magnetic field diagnostics of the corona and solar wind. In addition, radio observations toward exoplanet host stars give important constraints on the habitability of exoplanets. In this presentation, we will introduce the facilities, relevant radio astronomical diagnostics, early results, and plans for using the observations for data assimilation. 

How to cite: Cheung, M., Ekers, R., Morgan, J., Chhetri, R., Waszewski, A., Hobbs, G., Kaur, D., Zic, A., Bhat, R., and Jin, M.: Space Weather with Radio Telescopes in Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15289, https://doi.org/10.5194/egusphere-egu23-15289, 2023.

Recent Venus missions (Venus Express and Akatsuki) provided a large-scale view of Venus atmosphere and discovered new phenomena, such as high-altitude extension of the mountain wave to the cloud layer and a dawn-dusk asymmetry in the ionospheric motion.  The superrotation of the cloud layer is assumed to be driven by the thermal tide but its relation to any meridional convection or waves is still unknown.  The key to understand all these phenomena is to determine the multi-step re-distribution of the absorbed solar radiation to other forms of energy: (1) internal energy; including temperature, latent heat, and chemical energy (2) kinetic energy both in large scale flows/waves and in minor deviations of convection motions, (3) electric energy including ionization.

To understand how the motion of Venus atmosphere is driven by the energy originating from the absorption of solar radiation, we proposed Venus Dynamics Tracer (VdT), a mission for in-situ measurements, as a response to the ESA call for new M-class missions.  Specific targets were two major energy absorption regions: the cloud layer and the ionized upper atmosphere. The scientific goals were to investigate (a) the roles of the vertical and meridional circulation in maintaining major atmospheric dynamics near the cloud layer where visible light is absorbed and drives the vertical motions of the air, and to understand the (b) global dynamics of ions and neutrals in the upper atmosphere where EUV is absorbed both by neutrals and ions and where energy and momentum are transferred between them. 

For the first target, multiple-balloons are deployed for in situ observations with supporting camera/s on an orbiter giving global context. For the second target, the motions of ions and neutrals are directly measured.  This presentation discusses required measurements to answer the scientific goals.  

How to cite: Stenberg Wieser, G., Yamauchi, M., and Persson, M.: Venus Dynamics Tracer (VdT) - a mission dedicated for in-situ measurements of the Venus atmosphere., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16422, https://doi.org/10.5194/egusphere-egu23-16422, 2023.

The Voyager space probes provided us with a global perspective on galactic cosmic ray transport through the heliosphere at low to moderate heliographic latitudes, as well as their behavior at the boundary with the very local interstellar medium (VLISM). There remain, however, multiple interesting region the Voyagers have not visited, including high latitudes and the distant flanks of the heliopause where long-term trapping of charged particles is though to take place. We attempt to fill the gaps in our understanding of the distant heliosphere using computer simulations. The Space Plasma and Energetic Charged particle TRansport on Unstructured Meshes (SPECTRUM) code is a versatile software platform to perform tracing of particle trajectories using multiple physics models and internal or externally provided MHD background data. We apply the model to the problem of galactic cosmic ray transport in the outer heliosphere and the surrounding very local interstellar medium (VLISM) using the MHD background provided on a adaptive block mesh from the Space Weather Modeling Framework (SWMF). We compare the guiding center and nearly isotropic (Parker) physics models and elucidate the role of perpendicular diffusion in cosmic-ray penetration through the heliospheric boundary.

How to cite: Florinski, V., Alonso Guzman, J., Opher, M., and Ghanbari, K.: A new approach to modeling galactic cosmic rays in the heliosphere using arbitrary data driven MHD backgrounds, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16967, https://doi.org/10.5194/egusphere-egu23-16967, 2023.

Firefly is an innovative mission concept study for the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033 to fill long-standing knowledge gaps in Heliophysics. A constellation of spacecraft will provide both remote sensing and in situ observations of the Sun and heliosphere from a whole 4π-steradian field of view. The concept implements a holistic observational philosophy that extends from the Sun’s interior, to the photosphere, through the corona, and into the solar wind simultaneously with multiple spacecraft at multiple vantage points optimized for continual global coverage over much of a solar cycle. The mission constellation includes two spacecraft in the ecliptic and two flying as high as ~70º solar latitude. The ecliptic spacecraft will orbit the Sun at fixed angular distances of ±120º from the Earth. Firefly will provide new insights into the fundamental processes that shape the whole heliosphere. The overarching goals of the Firefly concept are to understand the global structure and dynamics of the Sun’s interior, the generation of solar magnetic fields, the origin of the solar cycle, the causes of solar activity, and the structure and dynamics of the corona as it creates the heliosphere. We will provide an overview of the Firefly mission science and architecture and how it will revolutionize our understanding of long-standing heliospheric phenomena such as the solar dynamo, solar cycle, magnetic fields, solar activity, space weather, the solar wind, and energetic particles

How to cite: Raouafi, N. E. and the The Firefly Constellation Team: The Firefly Constellation: The Need for a Wholistic View of the Sun and its Environment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17230, https://doi.org/10.5194/egusphere-egu23-17230, 2023.

The space environment simulation facilities are the key to any successful space experiments and missions. To characterize and validate the optical space instrument, Shenzhen university is started to design a large vacuum chamber with various integrated standard radiation sources, covering a wavelength range from UV to near-infrared. The large radiometry calibration facilities (LRCF) will be traced to standard scale factors such as those maintained by the World Radiation Center at the Physikalisch Meteorologisches Observatorium Davos, Switzerland. In this presentation, we will introduce the LRCF and the broadband radiometer developed for the moon-based earth observation system and how to use the LRCF to characterize the radiometer.

How to cite: Zhu, P., Liu, H., Song, M., Huang, S., and Li, Q.: The deep space environment simulation vacuum chamber and large radiometry calibration facilities at Shenzhen University, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4478, https://doi.org/10.5194/egusphere-egu23-4478, 2023.

Earth Radiation Budget (ERB) measurement is one of the main missions of Chinese second generation of polar orbiting meteorological satellites ---FengYun-3 (FY-3) series. There are two instruments, the Solar Irradiance Monitor(SIM) and the Earth Radiation Budget (ERB), on board FY-3 satellite to observe the earth incoming and reflected solar radiance and the emitted radiance.  The ERMs on FY-3/A/B/C observe the Earth atmosphere within a narrow scanning field of view (NFOV）and a wide non-scanning field of view (WFOV). For each field of view, the measurements are made from two broadband channels: a total waveband channel covering 0.2 – 50 μm and a Short Wave (SW) band covering 0.2 - 4.3 μm. Because the sudden degradation happened that the SW channel of NFOV has stopped working after 20 months for FY-3A and 8 months for FY-3B in orbit. The observation from ERM on FY-3C has been in good condition for 9 years  In this presentation the performance of ERMs calibration in orbit is evaluated with CERES from EOS/Aqua and GERB-3 from Meteosat. The ERM LW and SW unfiltered radiance produced with spectral correction based on atmospheric transfer modelling has a good consistence with the other data. The new ERM instrument(ERM-II), which has a broadband LW channel covering 5-50 μm besides the Total and SW channels with a NFOV scanning mode, will be launch in the coming 2023 and provide 8 years global ERB observation from next FY-3 morning satellite.

How to cite: Qiu, H. and Qi, J.: Earth Radiation Budget Measurements on Chinese FY-3 Series Polar Orbit Satellites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4590, https://doi.org/10.5194/egusphere-egu23-4590, 2023.

Global climate change has aroused widespread concerns in society regarding the sustainable development of human beings. The Earth’s radiation budget (ERB) at the Top-of-Atmosphere (TOA) includes incident solar radiation, Earth-reflected shortwave radiation, and outgoing longwave radiation. The accuracy of the existing spaceborne instruments still cannot meet the measurement requirement of the Earth’s TOA shortwave and longwave radiation. In recent years, several novel observing platforms and sensors have been proposed for ERB. Hitherto, most of those concepts for ERB are still in the phase of design and development, and studies have been mainly carried out based on simulations. Simulating the sensor-measured signals of the proposed novel platforms, sensors or constellations could help to optimize the sensor parameters, determine the number of satellites in the constellation, explore their potentials in characterizing the ERB. The anisotropic factor, depicting the anisotropy of Earth’s radiation, is essential in the simulation. However, developing angular distribution models involves complex procedures of data preparation, processing, and modeling. This study, targeting at simplifying the procedure of simulating the signals of ERB sensors, proposed an approach of estimating the longwave anisotropic factors directly from the Earth’s radiative fluxes. The approach was implemented with CERES data and the neural network algorithm. Models were developed for 10 scene types based on Earth’s surface types. Results showed that the longwave anisotropic factors were accurately estimated with the correlation coefficient (r) varying between 0.85 and 0.98 and MAPE within 1.20% for the test dataset. With the estimated anisotropic factors, the sensor-measured radiances were accurately retrieved with r=1.00 and MAPE=0.53%. Therefore, the proposed approach is promising in accurate and efficient simulations of novel ERB platforms and sensors like the Moon-based Earth Radiation.

How to cite: Liu, H., Zhu, P., Huang, S., and Li, Q.: Estimating the Anisotropic Factor of Angular Distribution Models from Radiative Fluxes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4921, https://doi.org/10.5194/egusphere-egu23-4921, 2023.

The  long-term millennial oscillations of the baseline  solar background magnetic field (SBMF) and the ephemeris of  the Sun-Earth distances are compared with the oscillations of solar irradiance at the terrestrial biomass (Hallstatt's cycle).    

Based  the Sun-Earth distances derived from the current JPL ephemeris based on solar inertial motion and gravitational effects on the Sun by four large planets: Jupiter, Saturn, Neptune and Uranus we  demonstrate the S-E distance is reduced by 0.005 au in the millennium M1 600-1600 and 0.011 au in millennium M2 1600-2600. We show that variations of the Sun-Earth distances  are accountable for the increase of the solar irradiance by about $20-25$ $Wm^{-2}$ since 1700 that will continue to last until 2500. he decrease of the S-E distance per century in the current millennium follows the  rate of the terrestrial temperature increase reported since MM. We evaluate that this difference of the Sun-Earth distances caused by SIM  leads to the different magnitudes of solar irradiance deposited in the Northern and Southern hemispheres  in M2 with thee Northern hemisphere to obtain more radiation compared to the Southern one. These estimations show that in the next 600 years the Sun will continue moving towards the Earth  that will result in a further increase of solar irradiance and the baseline terrestrial temperature  in 2500-2600. These variations are expected to be over-imposed by a reduction of solar activity during two grand solar minima (GSMs) with a reduce terrestrial temperatures by 1C  to occur  in 2020-2053 and 2370-2415. 

How to cite: Zharkova, V., Vasilieva, I., and Popova, E.: Solar total radiation input and terrestrial temperature in the two millennia of 600-2600, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5900, https://doi.org/10.5194/egusphere-egu23-5900, 2023.

Monitoring accurately the amount of the incoming solar radiation reaching the ground surface and the outgoing radiation at the top of the atmosphere (TOA) is crucial for quantifying the earth's energy budget as well as for understanding and modelling the climate system and its evolution. In the present investigation, we explore the use of the Geant4 Monte Carlo toolkit and a new reference spectrum SOLAR/SOLSPEC [1] to develop a new model to estimate the spectral distribution of Top of Atmosphere Outgoing Radiation (TOR). The system is implemented in Geant4, a toolkit [2] that simulates the passage of particles through matter. SOLAR-ISS is a high resolution solar spectrum with a mean absolute uncertainty of 1.26% at 1σ. The TOR is estimated for a clear atmosphere and at different air mass (AM). For quality analysis, the performance of this model is examined and evaluated by comparing Geant4 simulation results with those of the DISORT code, where the relative mean difference is less than 7.29% overall the spectral domain from 280 to 3000 nm for a well defined case. The characteristics, such as transmittance and reflectance, etc., of the present and previous results will be analysed and compared to evaluate the performance of Geant4. We can upgrade the current tools with more powerful, efficient, and accurate prototyping. Furthermore, We will consider the design of a graphical user interface for the creation of the simulation input file, this utility will serve as a guideline that helps the user to run a simulation.

How to cite: Boudjella, M. Y., Belbachir, A. H., Dib, S. A. A., and Meftah, M.: A new approach to determine the Top of Atmosphere earth Outgoing Radiation using the Geant4 toolkit, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7190, https://doi.org/10.5194/egusphere-egu23-7190, 2023.

The Earth Radiation Budget at the Top of the Atmosphere (ToA) governs the status of climate change on our planet. The ERB is the balance between the incoming Total Solar Irradiance (TSI) and total outgoing radiation at the ToA. If more energy is stored in the system the Earth Energy Imbalance is positive and the temperature in the system rises. The Compact Lightweight Absolute RAdiometer (CLARA) experiment onboard the Norwegian micro satellite NorSat-1 is an SI traceable radiometer with the primary science goal to measure TSI from space. Besides TSI, CLARA also measures the terrestrial Outgoing Longwave Radiation (OLR) at the ToA on the night side of Earth. We present the latest status of the data and degradation correction obtained with this SI-traceable radiometer and compare the CLARA TSI and OLR time series with other available observations and reanalysis data. The validation of these measurements is key to advance our capability to determine the Earth Energy Imbalance from space. 

How to cite: Haberreiter, M., Finsterle, W., Montillet, J.-P., Gyo, M., Pfiffner, D., Mostad, M., Spydevold, I., Beattie, A., Andersen, B., and Schmutz, W.: Total Solar Irradiance and Terrestrial Outgoing Longwave Radiation Measurements obtained with CLARA onboard NorSat-1, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7221, https://doi.org/10.5194/egusphere-egu23-7221, 2023.

The Project for On-Board Autonomy-3 (PROBA-3) is the fourth satellite technology development and demonstration precursor mission within ESA's GSTP (General Support Technology Program) series. The primary mission objective is to demonstrate the technologies required for formation flying of multiple spacecrafts. The PROBA-3 mission concept comprises two independent minisatellites in highly-elliptical Earth orbits in precise formation flying, close to one another with the ability to accurately control the attitude and separation of the two satellites. The mission launch is scheduled for end of 2023.

PROBA-3 mission consists of a coronograph spacecraft, hosting the coronograph APIICS, and the occulter spacecraft with the Digital Absolute RAdiometer (DARA).  The radiometer to record total solar irradiance is mounted on the front satellite pointing to the Sun. DARA is  developed and manufactured in Switzerland by the PMOD/WRC. We have done two pre-flight calibration campaigns: one at the World Radiation Center in Davos, Switzerland, and one at the Total Solar Irradiance (TSI) Radiometer Facility of the Laboratory for Atmospheric and Space Physics in Boulder Colorado, USA. We report on the results of the laboratory comparisons and discuss uncertainties of several instrument parameters, which are used to transform the raw measurements, which are voltage and current, into solar irradiance values. 

How to cite: Montillet, J., Schmutz, W., Finsterle, W., Kopp, G., Koller, S., Pfiffner, D., Gyo, M., Soder, R., Gander, M., Beeler, L., Langer, P., Spescha, M., Schlatter, P., Föller, J., Haberreiter, M., Heuerman, K., and Zukhov, A.: The DARA/PROBA-3 radiometer: results from the preflight calibration campaign, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9007, https://doi.org/10.5194/egusphere-egu23-9007, 2023.

The ACS-NIR spectrometer on board the Trace Gas Orbiter (TGO) is currently used to probe the atmosphere of Mars. It is, however, capable of measuring the near-infrared solar spectrum in the 0.7-1.7 µm domain with high spectral resolution when pointed at the Sun and its line of sight is above the atmosphere of Mars i.e. with its Solar Occultation mode. Specific observations were therefore made during 10 months in order to construct the solar spectrum in this spectral domain. The observations consist in recording all the diffraction orders of ACS-NIR by continuously varying the frequency of its AOTF (Acousto-Optic Tunable Filters, a component used to separate the orders). We will first present how we have treated each order of diffraction to improve the solar spectrum on the 0.7-1.7 µm band by considering for this purpose off-center images attached to certain AOTF frequencies. This method makes it possible to avoid contamination between the successive diffraction orders but also to increase the detection of the solar lines at the ends of each order where the intensity is low due to the Blaze function. We will then show the final version of the solar spectrum that we obtain. It will be compared to the reference spectrum, which is that of Toon. We will finish by showing and discuss some results revealing new solar lines appearing in certain diffraction orders of the ACS-NIR spectrometer and which are not present in the corresponding parts of the reference solar spectrum. 

How to cite: Irbah, A., Bertaux, J.-L., Montmessin, F., Trokhimovskiy, A., Korablev, O., and Fedorova, A.: High-resolution solar spectrum obtained from TGO orbiting Mars reveals new solar lines in the 0.7-1.7 µm range, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9484, https://doi.org/10.5194/egusphere-egu23-9484, 2023.

The GOES-R series spacecraft include a new operational measurement for GOES satellites, the Magnesium II (MgII) core-to-wing index.  This solar activity proxy has been measured at a daily cadence beginning in 1978.  It is widely used in solar spectral irradiance models such as the NRLSSI CDR (Coddington et al. 2016).  The C Chanel of the Extreme and Ultraviolet Spectrograph (EUVSC) on GOES 16 began making operational MgII index measurements at high cadence in early 2017.  There are currently three such instruments in orbit on GOES 16, 17, and 18 as part of the EXIS suite of solar irradiance instruments.  In the past, the MgII index was only measured a few times per day, but EXIS makes measurements at a 3-second cadence to monitor rapid changes in the Sun.

In this presentation, we will describe the available data product and how it compares with previous measurements.  On long timescales it can be used to extend the historical record, and on short timescales it reveals solar activity of interest to space weather practitioners.

How to cite: Snow, M., McClintock, W., Machol, J., Eparvier, F., and Woodraska, D.: GOES EUVS Magnesium II Index: The beginning of a new climate data record, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10082, https://doi.org/10.5194/egusphere-egu23-10082, 2023.

The EXIS (Extreme ultraviolet and X-ray Irradiance Sensors) detectors on the GOES-R spacecraft (GOES-16, GOES-17 & GOES-18) use quad-diode Sun Positioning Sensors (SPS) to maintain precision pointing. The 4 Hz quad-diode signal is high-precision and we attempt to use this signal as a high-cadence proxy for Total Solar Irradiance (TSI) and use the MgII index + NRLSS2 models to predict high-cadence spectra. The quad-diode signal must be calibrated for spacecraft velocity (a 1AU correction), instrument temperature, and diode degradation with usage. In the 2nd year of this 3-year project, we report the progress of these calibrations and our efforts toward defining our TSI proxy and high-cadence spectral data products.

How to cite: Penton, S., Snow, M., Beland, S., Don, W., and Odele, C.: GHOTI: GOES-R High-cadence Operational Total Irradiance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10126, https://doi.org/10.5194/egusphere-egu23-10126, 2023.

The total solar irradiance (TSI) is Earth’s primary source of energy, and accurate knowledge of its value and variability is crucial for understanding Earth’s climate and variability. In order to continue the existing 44 year data record of TSI measurements from space, NASA is developing the Total and Spectral Irradiance Sensors (TSIS) -2 mission. TSIS-2 consists of the Total Irradiance Monitor (TIM) and Spectral Irradiance Monitor (SIM) on a free flyer satellite, with an anticipated launch in the latter half of 2024. The TSIS-2/TIM is the latest iteration of the TIM instrument, prior versions of which flew onboard the SORCE, TCTE and TSIS-1 missions, and a direct rebuild of the TSIS-1 instrument. We present the pre-flight ground calibration of the TSIS-2/TIM instrument and its uncertainties. A key difference between the calibrations of the TSIS-1 and TSIS-2 instruments is the use of a novel low noise ambient temperature radiometer for TSIS-2 that significantly reduces the uncertainty in validating the component level calibrations through an end-to-end measurement. We compare component level (e.g. aperture area, detector reflectance, etc.) measurements and uncertainties for TSIS-2 with those from TSIS-1, and focus on areas where the uncertainty analysis differs from that applied to TIM instruments on prior missions and the implications of these differences.

How to cite: Thiemann, E., Heuerman, K., Villani-Davila, A., and Richard, E.: The TSIS-2 TIM Instrument Pre-Flight Calibration and Uncertainty, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10290, https://doi.org/10.5194/egusphere-egu23-10290, 2023.

Libera, NASA’s first Earth Venture Continuity Mission, is in preparation to provide seamless continuity to current Earth outgoing radiance measurements conducted and processed by the Clouds and Earth’s Radiant Energy System (CERES) project. Leveraging advanced detector technologies, Libera will measure the broadband total, longwave, and shortwave radiances akin to CERES and achieve radiometric uncertainty of approximately 0.2%. Beyond the crucial radiation budget continuity goal, Libera will carry a fourth radiometer in the shortwave near-infrared to advance our understanding of shortwave energy deposition in the climate system, such as related to the characterization of processes relevant for shortwave absorption, climate feedbacks, and Earth’s albedo variability with added insight into hemispheric albedo symmetry given the hemispheric differences in ocean, continent and cloud distributions. We use global model simulations and radiative transfer calculations as proxies for Libera’s future data record to demonstrate applications of the shortwave sub-band knowledge in climate science. Although Libera’s absolute accuracy is unprecedented, it is still insufficient to adequately close Earth’s energy budget. We will therefore discuss current and future avenues to indirectly and directly measure EEI from space. The latter is potentially feasible through sensing radiation pressure-induced accelerations acting on near-spherical spacecrafts, which under optimal conditions, are directly proportional to the net radiative flux experienced at the satellite’s location. This approach has been considered in the past, and the feasibility to achieve a measurement accuracy within 0.3 Wm^-2 is currently under investigation. 

How to cite: Hakuba, M. Z., Pilewskie, P., and Stephens, G. and the Libera Science Team: On the future of Earth radiation and energy imbalance measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10751, https://doi.org/10.5194/egusphere-egu23-10751, 2023.

Monitoring the Earth Radiation Budget (ERB) and in particular the Earth
Energy Imbalance (EEI), is of paramount importance for a predictive
understanding of global climate change.   We propose the new Earth
Climate Observatory (ECO) space mission concept for the monitoring of
the EEI.

The EEI is defined as the small difference between the two nearly equal
terms of the incoming solar radiation, and the outgoing terrestrial
radiation lost to space. Making a significant measurement of the EEI
from space is very challenging, and requires a differential measurement
with one single instrument of both the incoming solar radiation and the
outgoing terrestrial radiation. The instrument that allows such a
differential measurement is an improved wide field of view electrical
substitution cavity radiometer.

The wide field of view radiometer will observe the earth from limb to
limb. A single measurement footprint is a circle with a diameter around
6300 km. For the discrimination of cloudy and clear skies, a higher
spatial resolution is needed. This will be obtained from two wide field
of view cameras, a visible wide field of view camera for the
characterisation of the spatial distribution of the reflected solar
radiation, and a thermal infrared wide field of view camera for the
characterisation of the spatial distribution of the emitted thermal
radiation.

How to cite: Smeesters, L., Dewitte, S., and Mauritsen, T.: The Earth Climate Observatory (ECO) space mission concept for themonitoring of the Earth Energy Imbalance (EEI), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12178, https://doi.org/10.5194/egusphere-egu23-12178, 2023.

INSPIRE-SAT 7 is a French 2-Unit CubeSat primarily designed for Earth and Sun observations.  This mission is part of the International Satellite Program in Research and Education (INSPIRE). This satellite will be deployed in Low Earth Orbit (LEO) in 2023 as the first step of the so-called ‘Terra-F’ constellation that will provide spatio-temporal resolution for Earth Energy Imbalance (EEI) measurements.

This new scientific and technological pathfinder CubeSat mission (INSPIRE-SAT 7) is equipped with various channels on all sides. Among them: the Total Solar Irradiance Sensor (TSIS) payload, the Ultra-Violet Sensor (UVS) using a new generation of solar blind detectors designed to monitor the integrated Solar Spectral Irradiance (SSI) in the Hertzberg continuum, and the Earth Radiative Sensor (ERS) payload, designed to measure some Earth’s Radiative budget (ERB) components such as the outgoing short and long wave radiation at the top-of-the atmosphere for climate change studies.

The Belgian Radiometry Characterization Laboratory (B.RCLab) of the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) is the partner responsible for the pre-flight absolute calibration and radiometric characterization of INSPIRE-SAT7 TSIS and UVS payloads.

In this work we will first describe the INSPIRE-SAT7 concept, design, scientific and operational objectives. We will then present B.RCLab facilities along with its radiometric characterization benches, including the absolute calibration capabilities and its traceability. Finally, the main results of the INSPIRE-SAT7 pre-flight calibration campaign, which took place in November 2022, will be presented. These results allowed to calculate the sensors on-orbit calibration coefficients that are crucial to perform traceable absolute EEI measurements. A radiometric comprehensive uncertainty budget will be presented along the sensors’ calibration coefficients.

How to cite: Van Laeken, L., Bolsée, D., Pereira, N., Meftah, M., Sarkissian, A., Damé, L., Dufour, C., and team, T. I.-S.: INSPIRE-SAT7: Pre-Flight radiometric validation and calibration of a miniaturized Earth’s Radiative Budget satellite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12185, https://doi.org/10.5194/egusphere-egu23-12185, 2023.

TRUTHS (Traceable Radiometry Underpinning Terrestrial- and Helio-Studies) is an operational climate mission, aiming to enhance up to an order-of-magnitude our ability to estimate the Earth radiation budget through direct measurements of spectrally resolved solar reflected Earth radiances and Sun irradiances becoming a ‘gold standard’ reference in support of climate emergency research and operational applications. It aims to establish a “metrology laboratory in space” by creating a fiducial, SI-traceable reference data set to cross-calibrate other sensors and improve the quality of their data.

TRUTHS main objective is to establish a reference baseline measurement (benchmark) of the state of the planet, against which past and future observations can be compared, in order to:

• allow climate model improvements and forecast testing, and
• provide observational evidence of climate change, including mitigation strategies in the shortest time possible.

TRUTHS will primarily measure the incoming and outgoing energy from the climate system with an accuracy needed to detect climate trends in the shortest possible time.

The datasets needed to meet this objective have many additional applications, such as:

• SI traceable measurements of the incoming and reflected solar spectrum, to address direct science questions.
• Operational products for removing radiometric biases in other satellite instruments by cross-calibration with TRUTHS data, improving accuracy and enabling inter-operability including improvement of retrieval algorithms.
• Transferring radiometric reference values to existing Cal/Val infrastructure, e.g. RadCalNet, Pseudo-Invariant Calibration sites, In-situ ocean colour reference observations; selected surface reflectance test-sites (fluxnet ..), both nadir and multi-angular; to the Moon.

The mission comprises an “agile” satellite capable to point and image the Earth, the Moon and the Sun in a polar orbit hosting the Hyperspectral Imaging Spectrometer (HIS) capable to provide an accurate, continuously calibrated, dataset of spectrally resolved solar and lunar irradiance and Top of Atmosphere (ToA) Earth-reflected radiance in the near-UV/Visible/NIR/SWIR (320 nm to 2400 nm) waveband with a spectral sampling between 2 and 6 nm and a spatial sampling of 50 m. The payload utilises a novel SI traceable on-board calibration system, the Cryogenic Solar Absolute Radiometer (CSAR), as part of an innovative On-Board Calibration System (OBCS), allowing the HIS observations to achieve its unprecedented in-space accuracy, targeting an expanded radiometric uncertainty tied to international SI standards of 0.3% (k=2).

TRUTHS is implemented by the European Space Agency (ESA) as a UK led Earth Watch mission in collaboration with Switzerland, Czech Republic, Greece, Romania and Spain. The mission was conceived by the UK national metrology institute, NPL, in response to challenges highlighted by the worlds space agencies, through bodies such as CEOS, in relation to interoperability and accuracy. The mission is being developed by an industrial consortium led by Airbus Defence and Space UK.

The TRUTHS mission targets a launch in 2030 with a minimal life-time of 5 years, and design goal to reach 8 years, of in-orbit operations. It will become part of a future fleet of SI-Traceable Satellites (SITSATs) currently being developed by different space agencies, including CLARREO-Pathfinder (NASA) and CSRB (CMA), and together with FORUM (ESA) and IASI-NG (EUMETSAT) will provide spectrally resolved Earth radiance information from the UV to the Far-Infrared in the coming decade.

How to cite: Fehr, T., Fox, N., Marini, A., and Remedios, J.: Traceable Radiometry Underpinning Terrestrial- and Helio- Studies (TRUTHS) – A ‘gold standard’ imaging spectrometer in space to support climate emergency reseaerch, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12399, https://doi.org/10.5194/egusphere-egu23-12399, 2023.

Fengyun 3 series (FY-3) is the second generation polar orbiting meteorological satellite in China. There are 5 satellites have been launched since the first satellite FY-3A in 2008. The solar irradiance is one of important parameters to measure by FY-3 series. The instrument to measure the solar irradiance is called Solar Irradiance Monitor (SIM). The SIM was deployed on the orbit since FY-3A (morning orbit AM) in 2008 and FY-3B (afternoon orbit PM) in 2010. SIM was upgraded to SIM-II mounted on FY-3C (AM orbit) in 2013. The sensitivity, absolute accuracy and stability of the instrument has been improved with the more accurate control on the solar disk tracking system and instrument environment temperature maintaining system. The SIM-II together with the Solar Spectral Irradiation Monitor (SSIM) have been deployed on the orbit mounted on FY-3E (early-morning orbit EM) in 2021. This presentation overviews the FY program. The specification and performance of SIM, SIM-II and SSIM have been illustrated. The measured Total Solar Irradiance (TSI) product has been compared with the similar measurements on SOHO/VIRGO, SORCE, TSIS-1, etc. The future plan for the solar measurements in FY-3 series has been presented in the last part.

How to cite: Zhang, P., Qi, J., Ye, X., Huang, Y., and Zhu, P.: Fengyun Program and Solar Observation Activities, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12518, https://doi.org/10.5194/egusphere-egu23-12518, 2023.

Fengyun-3E is an early-morning orbit meteorological satellite which provided more opportunity to observe solar activities and was launched on July 5, 2021. The total solar irradiance is measured by Solar Irradiance Monitor-II (SIM-II) which has been improved on degradation monitor compared to earlier Fengyun satellite. The spectral solar irradiance is observed by the new payload Solar Spectral Irradiance Monitor (SSIM) which could provide continuous spectra from 165nm~2400nm. The SSIM instrument has three wavebands: UV band from 165 nm to 320 nm, VIS band from 285 nm to 700 nm, NIR band from 650 nm to 2400 nm, with spectral resolution as 1nm, 1nm and 8nm, respectively. In this work, we will present the design of solar observation, instruments on-orbit performance and preliminary results of FY-3E solar measurement.

How to cite: Qi, J., Zhang, P., Qiu, H., Sun, L., Ye, X., Fang, W., and Huang, Y.: The TSI and SSI measurement from Fengyun-3E Satellite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13188, https://doi.org/10.5194/egusphere-egu23-13188, 2023.

How to cite: Vasiuta, M., Tuppi, L., Penttilä, A., Muinonen, K., and Järvinen, H.: Validation of DSCOVR-based albedo estimate using a weather model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15415, https://doi.org/10.5194/egusphere-egu23-15415, 2023.

Solar irradiance is the main source of energy input to the planets of the Solar System. The solar rotation and the evolution of active regions on the surface of the Sun are two of the sources of solar irradiance variability. Nèmec et al. (2020) showed that the variability of solar irradiance is dominated by one of these two sources depending on the timescale of interest. The solar rotation dominates the variability for periods between 4-5 days and the synodic solar rotation period (27.3 days), while the evolution of active regions dominate for the remaining timescales.

Usually, the irradiance measurements at Earth are extrapolated to estimate the irradiance at other planets and study the effect of solar irradiance on other planets' atmospheres (Thiemann et al., 2017). In this "lighthouse model", the irradiance source regions on the surface of the Sun are assumed to simply rotate with a Carrington sidereal period of 25.38 days. This means that the solar rotation is the only cause of variability of the irradiance in this model, and the evolution of active regions is neglected.

In this work, we develop a model to calculate the irradiance at other planets by accounting for the evolution of magnetic features. Our method follows the Spectral And Total Irradiance REconstruction (SATIRE; Fligge et al. 2000; Krivova et al. 2003) approach and works by Nèmec et al. (2020) and Sowmya et al. (2021). First, the Surface Flux Transport Model (SFTM; Cameron et al. 2010) is used to obtain the time-dependent surface distribution of magnetic features (faculae and spots). Then, the solar irradiance is calculated as the sum of the contributions from the quiet Sun (i.e., regions with no magnetic activity), faculae, and spots. 

Our method allows calculating the solar irradiance directly at a given position within the ecliptic, regardless of the position of the Earth. We compare our irradiance calculations with those of the extrapolation method. We find that taking the evolution of active regions into account improves the estimation of solar irradiance significantly, especially when it comes to wavelengths in the visible and infrared ranges. Therefore, we suggest that our method provides more accurate estimates of solar irradiance to be used as input in studies of planetary atmospheres.

We would like to note that our method of irradiance calculation is currently only statistical. We use the SFTM as we do not have information of the areas of the far-side of the Sun, which are needed in order to get the correct rotational variability. To determine real daily values of irradiance, we need to combine our calculations with methods of helioseismology, which is still a work in progress.

How to cite: de Oliveira, I., Sowmya, K., Nèmec, N.-E., and Gizon, L.: Solar irradiance estimation for planetary studies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15701, https://doi.org/10.5194/egusphere-egu23-15701, 2023.

Knowledge of solar irradiance variability is critical to Earth's climate models and understanding the solar influence on Earth's climate. Direct measurements of the Total Solar Irradiance (TSI) have only been available since 1978 from instruments onboard multiple missions. Different calibrations of the individual instruments make estimates of the possible long-term trend in the TSI still uncertain. Knowledge of the Solar Spectral Irradiance (SSI) is even more undetermined. Here we use the carefully reduced observations from the Rome Precision Solar Photometric Telescope (Rome/PSPT) and semi-empirical irradiance models to reconstruct solar irradiance variations over the period 1996-2022. Results are discussed with respect to direct measurements and existing composite reconstructions.

How to cite: Ermolli, I. and Chatzistergos, T.: Reconstructing solar irradiance over the period 1996-2022, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16293, https://doi.org/10.5194/egusphere-egu23-16293, 2023.

The Solar Radiation and Climate Experiment measured Total Solar Irradiance (TSI) 
and Solar Spectral Irradiance (SSI) from 2003 to 2020. The Solar Irradiance Monitor (SIM) 
instrument measured SSI from 200nm to 2400 nm on a daily basis. The current SORCE-SIM
instrument degradation correction uses a measurement equation derived from
accessible telemetry, the known instrument refraction geometry, inter-detector comparisons,
and inter-spectrometer comparisons. While the current degradation model captures much of the
long-term trending, some of the parameters were adjusted without well-defined physical
interpretations.

The degradation model used for SORCE-SIM is not unique. We're reporting on work to Explore New
Instrument degradation Models and Algorithms (ENIGMA) to address issues with the current
model and with the derived corrected irradiances. The development of enhanced SORCE-SIM
measurement equations permits the evaluation, and potential inclusion, of degradation
mechanisms not captured in the present model.

We present an initial updated degradation model which improves our ability to construct a 
composite irradiance time series in combination with TSIS-SIM, whose measurements overlap 
with SORCE for 2 years and has well-defined uncertainties. Combining the two datasets, allowed
the construction of a consistent composite irradiance time series from 2003-2023. 

How to cite: Béland, S. and Penton, S.: Exploring New Instrument deGradation Models and Algorithms (ENIGMA), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16858, https://doi.org/10.5194/egusphere-egu23-16858, 2023.

The Fengyun 3E (FY3E) spacecraft was launched on the 4th of July 2021 at 23h 28min UTC according to CASC (China Aerospace Science and Technology Corp.) on a Long March 4C vehicle from JSLC (Jiuquan Space Launch Center) in China. The orbit is a sun-synchronous near-circular with an altitude of 800 km, and an inclination of 98.7 degrees. The nominal lifetime of the satellite is eight years. The JTSIM experiments belong to the solar activities monitoring package. The solar radiation is absorbed by the black-coated cavity and the induced different heat-flux between the primary and reference cavity is measured, and the electrically calibrated differential heat-flux is used to compute the solar irradiance. SIAR has three identical channels A, B, and C, and each channel has a different solar exposure time to study the instrument’s nonlinear drift due to degradation. DARA also has three cavity radiometers and electrical substitution radiometers (Channel A, Channel B, and Channel C). The difference is that they are aligned in a triangle. Compared to VIRGO/PMO6, DARA inverts the aperture geometry to eliminate stray light. DARA and SIAR absolute radiometers are not operating at the same time due to the different designs and measurement sequences. On August 18, 2021, both instruments successfully passed the first commission phase, and they started to observe the total solar irradiance since then.

How to cite: Ye, X., Zhu, P., Montillet, J.-P., Hu, X., Wang, J., Yang, D., Qi, J., Finsterle, W., Zhang, P., Fang, W., Koller, S., Pfiffner, D., Song, B., Luo, Z., Wang, K., Haberreiter, M., Wu, D., and Schmutz, W.: The first light from the joint total solar irradiance measurement experiment onboard the FY3-E meteorological satellite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17162, https://doi.org/10.5194/egusphere-egu23-17162, 2023.

Measurements of the plasma parameters of coronal mass ejections (CMEs), particularly the magnetic field and non-thermal electron population entrained in the CME plasma, are crucial to understand their propagation, evolution, and geo-effectiveness. Spectral modeling of gyrosynchrotron (GS) emission from CME plasma has been regarded as  one of the most promising methods to estimate spatially resolved CME plasma parameters remotely. The very low flux density of CME GS emission, however, makes this rather  challenging. This challenge has recently been overcome using the high dynamic range imaging capability of the Murchison Widefield Array (MWA). Although the detection of GS is now possible routinely, the large number of free parameters of the GS models and some degeneracies between the values of these parameters make it hard to estimate all of them from the observed spectrum alone. These degeneracies can be broken using polarimetric imaging. In this work, we demonstrate this using our newly developed capability of robust polarimetric imaging on the data from the MWA. Very interestingly, we find that spectro-polarimetric imaging not only breaks the degeneracies but also provides tighter constraints on a larger number of plasma parameters than possible with total intensity spectroscopic imaging alone. 

How to cite: Kansabanik, D., Mondal, S., and Oberoi, D.: Deciphering Faint Gyrosynchrotron Emission from Coronal Mass Ejection using Spectro-polarimetric Radio Imaging, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-485, https://doi.org/10.5194/egusphere-egu23-485, 2023.

We provide exact analytical solutions for the magnetic field produced by prescribed current distributions located inside a toroidal filament of finite thickness. In application to the MHD equilibrium of a twisted toroidal current loop in the solar corona, the Grad-Shafranov equation is decomposed into an analytic solution describing an equilibrium configuration against the pinch-effect from its own current and an approximate solution for an external strapping field to balance the hoop force.  Our solutions can be employed in numerical simulations of coronal mass ejections. When superimposed on the background solar coronal magnetic field, the excess magnetic energy of the twisted current loop configuration can be made unstable by applying flux cancellation to reduce the strapping field. Such loss of stability accompanied by the formation of an expanding flux rope is typical for the Titov-Dèmoulin eruptive event generator. The main new features of the proposed model are:

i)   The filament is filled with finite β plasma with finite mass and energy,
ii)  The model describes an equilibrium solution that will spontaneously erupt due to magnetic reconnection of the strapping magnetic field arcade, and
iii) There are analytic expressions connecting the model parameters to the asymptotic velocity and total mass of the resulting CME, providing a way to connect the simulated CME properties to multipoint coronograph observations.

How to cite: Sokolov, I., Gombosi, T., and Zhao, L.: A Titov-Dèmoulin Type CME Generator for Finite β Plasmas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2405, https://doi.org/10.5194/egusphere-egu23-2405, 2023.

Coronal Mass Ejections~(CMEs) are extremely dynamical large scale events in which plasma-not only the coronal plasma-is ejected into the interplanetary space. Their interplanetary counterparts measured in-situ are Interplanetary Coronal Mass Ejections (ICMEs), which is also an important part of space weather.

Even though the kinetic properties of the plasma might change because of dynamic effects occurring during the expansion of the CME, the heavy ion characteristics remain unchanged after it leaves the low corona. Charge states of heavy ions reflect important information about the coronal temperature profile due to the freeze-in effect, while elemental abundances indicate potential source regions of the plasma.

With the help of the Pulse Height Analysis (PHA) data from the Solar Wind Ion Composition Spectromet (SWICS) on board the Advanced Composition Explorer (ACE), combined with a newly developed multi-population model, we are able to conduct a high time resolution (12 minutes) case study on a complex ejecta detected by ACE in May 2005. This case lasted more than 80 hours and caused a strong geomagnetic response, with a Dst index at -247.

Multiple discontinuous periods with highly charged heavy ions are identified, elemental abundances also differ during those ”hot” periods. Heavy ion characteristics provide us an unique opportunity to see the boundaries of different parts of an ICME.

How to cite: Gu, C., Heidrich-Meisner, V., and Wimmer-Schweingruber, R. F.: Variations of high time resolution heavy ion characteristics in the complex May 2005 ICME, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2841, https://doi.org/10.5194/egusphere-egu23-2841, 2023.

Coronal mass ejections (CMEs) interact with large-scale solar wind structures and other CMEs during their propagation in the heliosphere and undergo erosion, deflection, and deformation. In this work, we aim to quantify the erosion of the CMEs in different solar wind backgrounds using 3D MHD simulations. The EUropean Heliosphere FORecasting Information Asset (EUHFORIA; Pomoell and Poedts, 2018) is employed to create a relaxed solar wind background and evolve a CME on top of it between 0.1 au and 2 au. The LFF spheromak model is used to model the CME. Initially, we assume a simple dipolar background wind mimicking a solar minimum condition. CMEs with different geometric and magnetic field parameters (geometrical size, chirality, polarity, and magnetic flux) are evolved, and the evolution of the CME mass and the magnetic flux contained in the magnetic cloud is tracked to quantify mass and flux erosion. We also quantify the deformation of the CME during its evolution by parameterizing the separatrix surface of the magnetic cloud. The same experiment is repeated in the presence of a stream interaction region (SIR) interacting with the CME. We characterise the deformation of the different sides of the CME (with and without the interaction with SIR). In addition, we explore the adaptive mesh refinement and stretched grid features of the upgraded EUHFORIA heliospheric wind model, i.e., the newly developed ICARUS model (Verbeke et al., 2022) to resolve the CME shock and magnetic cloud and find the conditions to improve the modelling of the sheath region. Although the analysis of CME erosion has been carried out in 2.5D (axisymmetric) in previous works (Hosteaux et al., 2021), we explore the differences in 3D, which is required to fully quantify the erosion and deformation, and investigate their effect on the CME arrival time and geo-effectiveness at Earth.

How to cite: Maharana, A., Vanwalleghem, Y., Baratashvili, T., and Poedts, S.: Quantifying the effect of CME erosion on geo-effectiveness using EUHFORIA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3444, https://doi.org/10.5194/egusphere-egu23-3444, 2023.

Coronal Mass Ejections (CMEs) are the main drivers of interplanetary shocks and space weather disturbances. Strong CMEs directed towards Earth can have a severe impact on our planet and their timely prediction can enable us to mitigate (part of) the damage they cause. One of the key parameters that determine the geo-effectiveness of a CME is its internal magnetic configuration.

The novel heliospheric wind and CME propagation model Icarus (Verbeke et al. 2022) which is implemented within the framework of MPI-AMRVAC (Xia et al., 2018) introduces new capabilities for better and faster space weather forecasts. Advanced numerical techniques, such as solution adaptive mesh refinement (AMR) and radial grid stretching are implemented. The different refinement and coarsening conditions and thresholds are controlled by the user. These techniques result in optimized computer memory usage and a significant execution speed-up, which is crucial for forecasting purposes. 

In this study we validate a new magnetized CME model in Icarus by simulating  interplanetary coronal mass ejections (ICMEs).  We chose particular CME events observed at different radial distances from the Sun by MESSENGER and ACE. We aim to model two CME events, to examine the capabilities of the model in different configurations. We identify the originating active region for the CME of interest, reconstruct its characteristic parameters and initiate the CME propagation inside Icarus with a spheromak CME model. We focus on estimating the accuracy of the arrival time, the shock strength and the magnetic field components of the CME model in Icarus. Using observations of different satellites we can track the propagation of the CMEs in the heliospheric domain and assess the accuracy of the model at different locations.

Different AMR criteria are used to achieve higher spatial resolutions at propagating shock fronts and in the interiors of the ICMEs. This way the complex structure of the magnetic field and the deformation and (plasma and magnetic flux) erosion can be simulated with higher accuracy due to the advantage of AMR. Higher resolution is especially important for the spheromak model, because the internal magnetic field configuration affects the CME evolution and its interaction with the magnetized heliospheric wind significantly. We assess the capabilities of AMR at different locations in Icarus. Finally, the obtained synthetic time-series of plasma quantities at different satellite locations are compared to the available observational data. As a result, Icarus allows us to model CMEs with higher accuracy, yet efficiently.

TB acknowledges support from the European Union’s Horizon 2020 research and innovation program under No 870405 (EUHFORIA 2.0) and the ESA project “Heliospheric modeling techniques” (Contact No. 4000133080/20/NL/CRS).

How to cite: Baratashvili, T., Grison, B., Schmieder, B., and Poedts, S.: Validation of the magnetized ICME model with a multi-spacecradt study in Icarus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3579, https://doi.org/10.5194/egusphere-egu23-3579, 2023.

Electrostatic wave instabilities induced by energetic electron beams are believed to be at the origin of radio emissions reported by the observations of interplanetary shocks and solar coronal sources. We revisit the electron beam-plasma configurations found susceptible to nonlinear radio (electromagnetic) emissions, but which led to contradictory outcomes both in the linear theory and especially in the numerical simulations. The results of a new dispersion and stability analysis are presented, in which the electron populations are modeled both with standard Maxwellian velocity distributions and with Kappa distributions revealed by in situ measurements. We thus describe not only the exact nature of these electrostatic fluctuations (e.g., electron beam modes, modified Langmuir waves, or electron acoustic waves), but also a series of characteristics that help to distinguish them in observations. The particle-in-cell simulations confirm the predictions of the linear theory, and show for the first time how the nonlinear radio emissions are modified due to the Kappa distributions of the electron populations.

How to cite: Lazar, M., Lopez, R. A., Shaaban, S. M., and Poedts, S.: The electrostatic electron beam-plasma instabilities and nonlinear radio emissions. Theory vs. PIC simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5303, https://doi.org/10.5194/egusphere-egu23-5303, 2023.

Coronal mass ejections (CMEs) are the largest type of eruption seen on our Sun and the primary cause of geomagnetic disturbances and storms when they arrive at the Earth. Most geomagnetic storms are created by the impact of single CME yet in a significant fraction of cases they are caused by the interaction of multiple CMEs or CMEs with other transient phenomena. In this paper we implement a spheromak CME description within our 3-D heliospheric MHD model and self-consistently model their interactions with the pre-existing solar wind and with one another. We assess their geo-effectiveness at 1 AU through quantification of the relevant solar wind variables and an empirical measures based upon solar wind-magnetosphere coupling functions. We show how the orientation and handedness of a given CME can have a significant impact on its geoeffectivness due to a prolonged conservation of toroidal flux caused by differential interplay with the Parker Spiral, and how a large range of possible CME-CME interactions can produce a diverse range of geophysical impacts at the Earth.

How to cite: Desai, R., Koehn, G., Davies, E., Forsyth, R., Eastwood, J., and Poedts, S.: Successive interacting coronal mass ejections: Preconditioning, magnetic reconnection and flux erosion: How to create a perfect storm?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5740, https://doi.org/10.5194/egusphere-egu23-5740, 2023.

Alfvénic fluctuations of various scales are ubiquitous in the solar wind, with their non-linear interactions and eventual cascade resulting in an important heating mechanism to accelerate the solar wind via turbulent heating. Such fluctuations are also present in other transient & coherent plasma structures such as Coronal Mass Ejections (CMEs), and exhibit varying properties as compared to the solar wind plasma. In this study we investigate the interactions between solar wind Alfvénic fluctuations and CMEs using MHD simulations. We use an ideal magnetohydrodynamic (MHD) model with an adiabatic equation of state. An Alfvén pump wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components, and a CME is injected by inserting a flux-rope modelled as a magnetic cloud into the quasi-steady solar wind.

We observe that upstream Alfvén waves experience a decrease in frequency and change in the wave vector direction due to the non-spherical topology of the CME shock front. The CME sheath inhibits the transmission of low frequency fluctuations due to the presence of non-radial flows in this region. The frequency of the solar wind fluctuations also affect the steepening of MHD fast waves causing the CME shock propagation speed to vary with the solar wind fluctuation frequencies.

How to cite: Sishtla, C., Pomoell, J., Kilpua, E., Good, S., and Vainio, R.: Modelling the Interaction of Alfvénic fluctuations with Coronal Mass Ejections in the low solar corona, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6807, https://doi.org/10.5194/egusphere-egu23-6807, 2023.

The problem of forecasting southward pointing magnetic fields in coronal mass ejections (CMEs) is closely tied to our ability to measure their magnetic field configuration between the Sun and 1 AU. I will review some of the ideas that have been developed to tackle this problem, from using solar proxies, heliospheric images, Faraday rotation and measuring the in situ magnetic field near the Sun Earth-line. Another way to make progress is to use the L1 data as boundary conditions for fast ensemble simulations, focusing on the flux rope parts inside CMEs. However, for any type of modeling and forecasting we need to better understand the global magnetic structure and shape of CME flux ropes from multi-spacecraft observations, now delivered by spacecraft such as Parker Solar Probe, Solar Orbiter, BepiColombo, STEREO-Ahead and Wind, ACE or DSCOVR. In the future, the PUNCH mission will allow for the first time to extract 3D information from heliospheric images, forming another trailblazer towards developing models for ESA's Vigil mission, and setting the stage for possible interplanetary fleets of small spacecraft.

How to cite: Möstl, C., Amerstorfer, U., Rüdisser, H. T., Weiss, A. J., Amerstorfer, T., Bauer, M., Davies, E. E., Bailey, R. L., and Reiss, M. A.: Forecasting southward pointing magnetic fields in solar coronal mass ejections, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7061, https://doi.org/10.5194/egusphere-egu23-7061, 2023.

We present the latest results in our ongoing work to construct a generalized analytical flux rope model. Our previously published writhed flux rope model is extended to include non-circular cross-sections to better mimic the magnetic field measurements that are seen in situ and imaging observations. We implement our new model within the scope of a fast forward simulation model that propagates a flux rope away from the Sun into the heliosphere and can generate synthetic magnetic field measurements at arbitrary positions. This flux rope is continuously deformed along its axis due to interaction with the ambient solar wind which is provided by other models. We use our model and the forward simulation in an attempt to reconstruct the global picture of a particular multi-point ICME event.

How to cite: Weiss, A. J., Nieves-Chinchilla, T., Reiss, M., and Moestl, C.: Modeling ICME flux ropes as bent and distorted tubes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7135, https://doi.org/10.5194/egusphere-egu23-7135, 2023.

Decades of observations have revealed that Coronal Mass Ejections (CMEs) come in a variety of forms. Some have a classic 3-part structure, whilst others can be fan shaped or jet-like. Some of these differences can be put down to projection effects, but differences in magnetic structure also play a key role. Observational and simulation studies are now highlighting that the path by which a CME flux rope traverses the solar corona, and in particular the magnetic structures it interacts with on the way, shape the ultimate characteristics of the CME further out in the heliosphere. Therefore, understanding the nature of CME flux rope interaction with the ambient corona is a key part of predicting their evolution through the heliosphere and ultimately their geoeffectiveness at Earth. In this talk I’ll discuss from a modelling perspective some recent efforts to understand this interaction process and what it tells us about CMEs on a range of scales.

How to cite: Wyper, P.: What impact does the pathway through the solar corona make on CMEs?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7312, https://doi.org/10.5194/egusphere-egu23-7312, 2023.

Propagation of interplanetary (IP) shocks, particularly those driven by coronal mass ejections (CMEs), is still an outstanding question in heliophysics and space weather forecasting. Here we address effects of the ambient solar wind on the propagation of two CME-driven shocks from Sun to Earth. The two CME-driven shock events (CME03: April 3, 2010 and CME12: July 12, 2012) have the following properties: (1) driven by a halo CME (i.e., source location is near Sun-Earth line), (2) a southern hemispheric CME source location, (3) similar propagation speed (e.g., took ~2 days reach the Earth), (4) occurred in the non-quiet solar period, and (4) leading to a severe geomagnetic storm. What is interesting is that the initial (near the Sun) propagation speed, as measured by coronagraph images, of CME03 was slower (~300 km/s) than CME12, but it took about same time for both events to reach the Earth. According to in-situ solar wind observations from Wind, the CME03-driven shock was associated with a faster solar wind upstream of the shock than the CME12. This is also demonstrated in our global MHD simulations. This study emphasizes the importance of the background solar wind in the propagation of CME-driven shocks. Not only the initial propagation speed near the Sun but also the ambient solar wind speed is the key to timing the arrival of CME events. The present study also demonstrated that global MHD simulations with realistic solar wind inputs is able to precisely predict the arrival of CME events.

How to cite: Wu, C.-C., Liou, K., wood, B., and Hutting, L.: Effects of background solar wind on the propagation of coronal mass ejection driven shock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7390, https://doi.org/10.5194/egusphere-egu23-7390, 2023.

Twist is an intrinsic property of magnetic flux ropes that aids in understanding their evolution and eruption. It can be difficult to compute, resulting in the common use of approximations that do not consider the geometry of the flux ropes. However, while these approximations are often relatively simple to compute, their results require careful evaluation to ensure they are correctly understood. Consequently, the magnetic field analysis tools (MAFIAT) Python package has been developed to compute the geometrically-based twist of coronal flux ropes. Here we describe MAFIAT’s initial features, its Jupyter notebook-based operation, its scientific relevance, and our plans for its future development.

How to cite: Price, D., Pomoell, J., and Kilpua, E.: MAFIAT: Magnetic Field Analysis Tools, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7413, https://doi.org/10.5194/egusphere-egu23-7413, 2023.

Our knowledge of the physical processes carrying information across Coronal Mass Ejections (CMEs), thereby controlling the way CME structures respond to external disturbances  in interplanetary space, is still incomplete. One prominent question is whether CMEs are “coherent” structures, i.e. potentially capable of responding in a uniform manner to external forces, and across what (macroscopic) spatial scales does such coherence exist. A necessary condition for different regions within a given CME to exhibit a coherent behavior is that they must be causally connected to the perturbation source. Past studies suggested interplanetary CMEs may behave as coherent structures only locally, and indicated that the spatial scale of coherence may be hampered by interactions with large-scale structures in the solar wind. Additionally, observational studies often assumed the correlation in the magnetic field profiles at different spacecraft locations as a proxy for coherence, but the physical link between correlation and coherence is still to be established. Characterizing the physical mechanisms mediating CME structural changes in different solar wind conditions at a fundamental level is therefore imperative to better understand their evolution and impact on space-borne and ground-based anthropic activities. 

In this study, we investigate the role of Alfvénic fluctuations (AFs) as mediators of coherence within interplanetary CMEs, and the physical relationship between correlation and coherence using multi-point observations near 1 au. In order to determine if and to what extent AFs alter CMEs at different spatial scales, we compare CME signatures at multiple spacecraft in terms of presence/absence of AFs, AF properties (if present), and correlation of magnetic signatures.  We contextualize the results in terms of the CME interaction history and the causal connection of different spacecraft observations. This study reveals how AFs affect the correlation of CME magnetic signatures across different spatial scales, and helps reconcile correlation scales within CMEs with their coherent behavior. 

How to cite: Scolini, C., Lugaz, N., Winslow, R., and Farrugia, C.: Multi-point Investigation of CME Alfvénicity and Coherence near 1 au, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7508, https://doi.org/10.5194/egusphere-egu23-7508, 2023.

Data-driven coronal models are attracting increasing attention for their ability to accurately capture the pre-eruption magnetic field configuration of active regions. However, the degree to which the current modelling techniques are able to provide information on the loss of stability and initial dynamics of the eruptions remains unclear. An interesting avenue for probing this is by employing time-dependent modelling such that the dynamic data-driving is switched-off at a given time. In this study, we investigate what we can learn from this relaxation procedure about the eruption itself and the instability that ultimately triggers it for at least two different active regions. To this effect, we use the time-dependent data-driven magnetofrictional model (TMFM) and perform multiple runs with varying relaxation times (i.e., time instances when the driving is switched off). Furthermore, we use two different physical models to simulate the coronal evolution after this point in time: the standard magnetofrictional method and a zero-beta MHD (magnetohydrodynamics) approach. In case of an eruption being triggered, the detailed evolution is characterised by tracking the associated magnetic flux rope which is extracted from the simulation data with a semi-automatic extraction algorithm. This flux rope detection and tracking procedure makes use of the twist number T_w, as well as the morphological gradient. For a further improvement of the extraction procedure, various mathematical morphology algorithms are performed to accurately extract the flux rope field lines. The properties of the extracted flux ropes are compared against their observational low-coronal manifestation in SDO/AIA data. 

How to cite: Wagner, A., Kilpua, E. K. J., Price, D. J., Pomoell, J., Poedts, S., Bourgeois, S., Kumari, A., Daei, F., and Sarkar, R.: Investigating Flux Rope Eruptivity via Time-dependent Data-driven Modelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8506, https://doi.org/10.5194/egusphere-egu23-8506, 2023.

Successful modeling of Coronal Mass Ejections (CMEs) is an important step towards accurately forecasting their space weather impact. Therefore, it is crucial to improve the various models, techniques and tools to reconstruct CMEs while validating simulations with observations of the solar corona and the inner heliosphere at various heliospheric distances with multi-viewpoint observations.

The Space Weather Modeling Framework (SWMF) includes MHD modeling of the solar wind and CMEs from the Sun to the Earth and beyond. The Alfven Wave Solar atmosphere Model (AWSoM) is a 3D extended-MHD solar corona model within SWMF that reproduces the solar wind background into which CMEs can propagate. The Eruptive Event Generator (EEG) module within SWMF is used to obtain flux-rope parameters to model realistic CMEs within AWSoM using different flux-rope configurations.

In this work supported by the NSF SWQU and LRAC programs, we use an ensemble of solar wind backgrounds to obtain the best solar wind plasma environments into which CMEs can be launched. We vary the flux-rope parameters within a fixed range and obtain an ensemble of CME simulations to match the model reconstructed results with remote coronagraph observations near the Sun (LASCO C2/C3 and STEREO COR1/COR2) as well as with in-situ observations of solar wind plasma at 1 au. The ensemble modeling is a step forward towards improving the accuracy of the tools that provide flux-rope parameter estimates as well as the uncertainty quantification of CME modeling.

How to cite: Sachdeva, N., Toth, G., Manchester, W., van der Holst, B., Jivani, A., and Chen, H.: Ensemble modeling of CMEs to reconstruct remote and in-situ observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8641, https://doi.org/10.5194/egusphere-egu23-8641, 2023.

Coronal holes (CH) are large, long-lived structures commonly observed in the solar corona as regions of reduced emission in EUV and X-ray wavelengths. They feature a characteristic open magnetic field configuration along which ionized electrons and atoms are accelerated into the interplanetary space. The resulting outflowing plasma is called high seed solar wind stream (HSS; see Cranmer 2009 and references therein). These HSSs are the major cause of minor to moderate geomagnetic activity at Earth (see Richardson 2018 and references therein).

To be able to predict the arrival and impact of those disturbances accurately, their origin and evolution need to be studied in detail. And to do so, it is imperative that CHs are accurately and reliably extracted, thus leading to the development of the Collection of Analysis Tools for Coronal Holes (CATCH). By using the intensity gradient across the CH boundary, it is possible to robustly extract CHs whose properties can then be analyzed. We find that the area of long-living CHs generally evolves by growing to a maximum before decaying. However, the associated magnetic field does not evolve equally. Depending on the CH, we find a correlation, an anti-correlation or even no correlation over the course of its lifetime. Therefore, we believe that the evolution of a CHs magnetic field is primarily driven by the large-scale connectivity changes in the Sun's global magnetic field. Further, we find that the plasma properties within CHs show a significant center to boundary gradient, which may justify the distance-to-boundary parameter used in some solar wind modeling.

To study the evolution of CHs in detail, a 360° view of the Sun is necessary; however, the magnetic far-side of the Sun still eludes. The few snapshots with Solar Orbiter provide only a fragmented picture of the magnetic field on the solar far-side. We found that by using EUV observations of the transition region (specifically using Stereo) it is possible to estimate the magnetic field density of CHs on the solar far side. In addition, we are currently investigating the incorporation of helioseismic observations into synoptic magnetograms to generate a maps that show the magnetic field of the whole Sun at a given time.

How to cite: Heinemann, S. G.: On the evolutionary aspects of solar coronal holes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8687, https://doi.org/10.5194/egusphere-egu23-8687, 2023.

It is widely known that the fast solar wind originates mainly from coronal holes (CHs) in the solar corona. Associations between the CH characteristics and the properties of the fast solar wind in situ have been studied throughout the years from different authors leading to diverse degrees of correlation (Nolte et al. 1976; Vršnak et al. 2007; Karachik et al. 2011; Rotter et al. 2012a; Hofmeister et al. 2018; Heinemann et al. 2020). In this work, we introduce and quantify the geometrical complexity of CHs, a parameter that has been neglected so far in similar studies. For a particular CH sample, we explore how complexity affects the peak speed of the fast solar wind at Earth and its association with other CH properties. We further compare observations of fast solar wind at Earth with forecasts from EUHFORIA. We evaluate our results, and present the efforts and restrictions we encounter towards improving our prediction capabilities by exploiting recent PSP observations.

How to cite: Samara, E., Magdalenic, J., Rodriguez, L., Poedts, S., Georgoulis, M. K., Pinto, R. F., Arge, C. N., Heinemann, S. G., and Hofmeister, S. J.: The fast component of the solar wind: origins, correlations and modeling with EUHFORIA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9486, https://doi.org/10.5194/egusphere-egu23-9486, 2023.

Interplanetary magnetic clouds with flux rope structures are an essential ingredient of space weather models. The main aim is to reconstruct their magnetic field topology and plasma properties and track their evolution in space and time. This has led to the implementation of a variety of flux rope configurations in magnetohydrodynamic models, with spheromak, modified spheromak, and more general toroidal flux ropes being commonly used.  

The spheromak implementation in EUHFORIA (EUropean Heliospheric FORecasting Information Asset) brought to light different manifestations in the simulation domain of a phenomenon called the spheromak tilting (instability). The latter is caused by a torque that is exerted on the spheromak when its magnetic moment forms an angle with the ambient field. The torque forces the spheromak to rotate until it reaches a state of reduced magnetic potential energy. This is a simplified description of the fact that the Lorentz force exerted by the ambient magnetic field on the toroidal currents in the spheromak has in general a rotational component, resulting in a net-torque. As not only spheromaks but also other types of flux ropes carry toroidal currents, these should experience a torque as well. To what extent it affects their evolution is a matter of a game of forces. Being thus able to track the evolution (the position, orientation, etc.) of flux ropes is crucial. 

We have developed a tool to perform such a tracking for the spheromak implementation in EUHFORIA. The tool uses magnetic field and plasma threshold criteria to locate the spheromak and estimate its magnetic moment. It was originally developed and applied to spheromaks inserted in synthetic uniform ambient plasma and unipolar ambient fields that are realistic only locally along the spheromak trajectories. Since its initial development, the tool has been further improved and made capable of dealing with more realistic ambient field scenarios, containing current sheets and high-speed streams. 

How to cite: Asvestari, E., Rindlisbacher, T., Pomoell, J., Kilpua, E., and Sarkar, R.: Tracking the evolution of spheromak flux ropes in ambient interplanetary magnetic field and plasma environments., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9898, https://doi.org/10.5194/egusphere-egu23-9898, 2023.

Observations of the solar wind at the close to the Sun distances by the Parker Solar Probe (PSP) show most of the time very strongly variable solar wind plasma characteristics. Inspecting the PSP observations during first ten perihelion, together with this large variability, we have also found a significant number of intervals of enhanced solar wind velocity appearing simultaneously with the decrease of the solar wind density, which indicates that this solar wind is originating from the coronal holes. However, out of thirty such intervals only few of them show velocity above 500 km/s. Majority of the identified wind flows have velocity of only about 400 km/s indicating that this solar wind will not be clearly distinguished as a flow when observed at 1 au distances. Employing the magnetic connectivity tool (developed by ESA’s MADAWG group) to associate the solar wind observed by the PSP with their source regions on the Sun, we identified the sources of that enhanced solar wind observed by the PSP to be the small coronal holes.

In this study we present the characteristics of a solar wind flows originating from such small coronal holes at close to the Sun distances and compare them with the characteristics of the fast solar wind originating from the large coronal holes. We also discuss on the possible reasons why we do not find more intervals of the fast solar wind in the PSP observations and compare the characteristics of solar wind observed at close to the Sun distances and at 1 au.

How to cite: Magdalenic, J., Valliappan, S. P., and Rodriguez, L.: Solar wind originating from the small coronal holes , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9944, https://doi.org/10.5194/egusphere-egu23-9944, 2023.

The Mercury Orbiter Radio-science Experiment (MORE), onboard the ESA-JAXA mission BepiColombo, is dedicated to the study of Mercury’s interior structure and rotational state, and to fundamental physics tests. The MORE radiotracking system relies on a multi-frequency radio link: the onboard Deep Space Transponder receives an uplink in X-band and retransmits it back coherently in X- and Ka-band, the Ka-band transponder allows to establish a two-way link in Ka-band.

During the cruise phase, BepiColombo experienced four superior solar conjunctions. These periods, spanning for 15 days centered about the minimum impact parameter of the radio path between the spacecraft and the Earth, are exploited for tests of relativistic delay and Doppler shift. Thanks to the multi-frequency link the signal due to the solar corona plasma can be isolated through precise calibrations, exploiting the dispersive nature of the plasma^1,2. This allows MORE to remove the plasma noise from the Doppler and range data in order to perform the fundamental physics test, but also to characterize the inner solar corona.

In this work we focus on the analysis of the data from the first (10^th-24^th March 2021) and second (29^th January - 12^th February 2022) solar conjunction experiments to characterize the properties of the solar wind.

For each radiotracking pass the power spectral density of Doppler measurements is compared with the expected power spectral index of a Kolmogorov turbulence (f^-2/3)³.

Solar corona plasma data are also used to localize the plasma structures of the solar corona along the line of sight by means of cross-correlations between uplink and downlink time series of the plasma content obtained from Doppler data. This allows us to analyze in more detail large solar phenomena, such as coronal mass ejections.

Exploiting the collected open-loop recordings at high frequency (4 kHz), the solar wind velocity can be estimated assuming a theoretical model for the intensity spectrum⁴. The intensity timeseries are used to fit theoretical spectrum parameters (amplitude, velocity, axial ratio, inner scale of turbulence and power law index), characterizing the solar wind in the vicinity of the Sun.   

Finally, the range data set allows us to retrieve the total electron content along the radio path. This absolute measurement is used to adjust models of the solar wind density beyond four solar radii.

¹ Bertotti et al, “Doppler tracking of spacecraft with multi-frequency links”,Astronomy and Astrophysics 269, 608-616, 1993

² Bertotti et al, “A test of general relativity using radio links with the Cassini spacecraft”, Nature 425, 374-376, 2003

³ R. Woo and J.W. Armstrong, “Spacecraft Radio Scattering Observations of the Power Spectrum of Electron Density Fluctuations in the Solar Wind”, Journal of Geophysical Research 84, no. Al2, 1979

⁴ S. L. Scott, W. A. Coles and G. Bourgois, “Solar wind observations near the sun using interplanetary scintillation”, Astronomy and Astrophysics 123, 207-215, 1983

How to cite: Doria, I., Cappuccio, P., and Iess, L.: Probing the solar corona with Doppler and range measurements of the spacecraft BepiColombo, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12917, https://doi.org/10.5194/egusphere-egu23-12917, 2023.

One of the major challenges in space weather forecasting is to reliably predict the magnetic structure of interplanetary coronal mass ejections (ICMEs) in the near-Earth space. In the framework of global MHD modelling, several efforts have been made to model the CME magnetic field from Sun to Earth. However, it remains challenging to deduce a flux-rope solution that can reliably model the magnetic structure of a CME. Spheromaks are one of the models that are widely used to characterize the internal magnetic structure of a CME. However, recent studies show that spheromaks are prone to experience a large rotation when injected in the heliospheric domain which may affect the prediction efficacy of CME magnetic field at 1 AU. Moreover, the fully inserted spheromaks do not have any legs attached to the Sun. In addition, due to the inherent topology of the spheromak, the in-situ signature may exhibit a double flux-rope-like profile not reproduced by standard locally cylindrical flux rope models. Aiming to study the dynamics of CMEs exhibiting different magnetic topologies, we implement a new flux-rope model in “European heliospheric forecasting information asset” (EUHFORIA). Our flux-rope model includes an initially force free toroidal flux-rope that is embedded in the low-coronal magnetic field. The dynamics of the flux rope in the low and middle corona is solved by a non-uniform advection constrained by the observed kinematics of the event. This results in a global non-toroidal loop-like magnetic structure that locally manifests as a cylindrical structure. At heliospheric distances, the evolution is modeled as a MHD process using EUHFORIA. We track the evolution of the flux-rope up to 1 AU and assess the model results with the observed in situ profile of the associated CME.  This work is an important step forward in developing a realistic CME model that can be used for reliable space weather forecasting.

How to cite: Sarkar, R., Pomoell, J., Kilpua, E., and Asvestari, E.: Implementing a toroidal flux rope model in EUHFORIA and assessing its performance in predicting CME magnetic-field at 1 AU, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13296, https://doi.org/10.5194/egusphere-egu23-13296, 2023.

Alfvén waves play an important role in the stability, heating, and transport of magnetized plasmas. They are found to be ubiquitous in the solar wind, mainly propagating outward from the Sun, especially in high-speed streams emanating from coronal holes. When high-speed streams impinge on the Earth’s magnetosphere, the impact of Alfvénic fluctuations can cause magnetic reconnection between the intermittent southward IMF and the Geomagnetic field, leading to energy injection from solar wind into the Earth’s magnetosphere. In this work, we tested a rotation procedure from the
Heliocentric Earth Ecliptic (HEE) to the Mean-Field Aligned (MFA) reference frame, identified by means of the Empirical Mode Decomposition (EMD), of both solar wind velocity and interplanetary magnetic field at 1 AU. Our aim is to check the reliability of the method and its limitations in identifying Alfvénic fluctuations through the spectral analysis of time series in the MFA reference frame. With this procedure, we studied the fluctuations in the main-field-aligned direction and those in the orthogonal plane to the main field. To highlight the peculiarities of each case of study and be able to better identify Alfvén waves when applying this procedure to real data, we reproduced the magnetic and velocity fields of a typical corotating high-speed stream. We tested the procedure in several cases, by adding the presence of Alfvén waves and noise. We performed the spectral analysis of the MFA component of both magnetic and velocity fields to define the power related to the two main directions: the one aligned to the ambient magnetic field and the one orthogonal to it. The efficiency of the procedure and the result’s reliability are supported by Monte Carlo tests. The method is as well applied to a real case represented by a selected corotating solar wind stream. The results are also compared with those obtained by using the Elsässer variables to analyze the Alfvénicity of fluctuations via the cross-helicity, which is related to the degree of correlation between the solar wind velocity and the magnetic field fluctuations.

How to cite: Carnevale, G., Regi, M., Francia, P., and Lepidi, S.: On the validation of the rotation procedure from HEE to MFA reference frame in presence of Alfvén waves in the interplanetary medium, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15636, https://doi.org/10.5194/egusphere-egu23-15636, 2023.

Coronal Mass Ejections (CMEs) carry large amounts of magnetized plasma into the heliosphere at very high speeds. Their interplanetary counterparts, or Interplanetary CMEs (ICMEs), create adverse space weather conditions around planets. These interplanetary structures have the potential to cause hazardous space weather and impact space- and ground-based technologies on Earth. At CESSI we have developed a 3D magnetohydrodynamic STORM Interaction (CESSI-STORMI) module to simulate the interactions between ICMEs and planets with and without a global magnetosphere. In this talk, I shall discuss our data-driven simulations to assess ICME impact on the Earth’s magnetosphere and  present a methodology to estimate their geo-effectiveness. We validate this module with observations and find a good match with the observed values of the Dst index for past events. In addition, we also present a qualitative study of the global magnetosphere under the influence of ICMEs. Our work allows us to estimate the severity of geomagnetic storms based on early, data-driven inputs of ICME flux rope profiles gleaned from near-Sun or in-situ observations. Thus our work has the potential to significantly extend the time window for predicting the severity of geomagnetic storms - which remains a grand challenge in heliophysics.

How to cite: Roy, S. and Nandy, D.: A magnetohydrodynamic modelling approach to simulate CME-forced planetary magnetospheres and predict geomagnetic impacts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16801, https://doi.org/10.5194/egusphere-egu23-16801, 2023.

How to cite: linan, L., Regnault, F., Perri, B., Brchnelova, M., Kuzma, B., Lani, A., and Poedts, S.: Modelling the propagation of flux ropes in the coronal model COCONUT, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17122, https://doi.org/10.5194/egusphere-egu23-17122, 2023.

The event of October 28 2021 was very geoeffective with particles accelerated to high energies resulting in ground level enhancements (GLEs). It is important to understand the scenario leading to such energetic particle acceleration which can be done by studying the origin of this event from the Sun to the Earth through the heliosphere.  The acceleration of particles was justified by two acceleration processes, one due to the flare during the impulsive phase, and the second by the coronal mass ejection (CME), which prolonged the low level proton emission (Zhang, Gan et al 2022, Klein et al 2022).

The first step of our study  was to understand the relationship between the  flare, the EUV wave and the CME  using the SDO, STEREO- A/COR1 and SOHO/LASCO observations (Devi et al 2022).  The second step was to model the CME (Guo et al 2023).

We found that a fast-mode EUV wave front propagates ahead  the CME front. The eruption was modeled by a flux rope using the Regularized  Biot-Savart Laws in a data-driven background obtained with HMI magnetograms. The CME was well recovered with its three components and the shock fitted with the observations.  We plan to study the evolution of  this flux rope in the solar wind by using  EUHFORIA.

How to cite: Schmieder, B., Guo, J. H., Devi, P., Chandra, R., Guo, Y., Chen, P. F., and Poedts, S.: Data-driven simulation of the coronal mass ejection of October 28 2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2002, https://doi.org/10.5194/egusphere-egu23-2002, 2023.

Resolving thermodynamic transport in three-dimensional models of stratified coronal loops is a long-standing challenge that limits progress in solving the coronal heating problem.
Since three-dimensional thermal conduction in MHD has been computationally too expensive to resolve the steep temperature gradients in the transition region, two simpler approaches have been adopted: one-dimensional, field-aligned models following the thermal response to imposed forms of heating, and three-dimensional MHD models that produce the forms of Ohmic and viscous heating self-consistently but cannot consider the consequent thermodynamic response.
Now, using a novel numerical technique, TRAC, we can resolve energetic transport in the transition region in fully three-dimensional MHD models.
In a model of a multi-stranded coronal loop in a curved arcade, we investigate the heating produced in an 'avalanche'-like process.
In such, a chain reaction of reconnection-induced local events occurs, with each event disturbing wider plasma and triggering other processes, such as shocks, jets, and turbulence, that generate heating, which we analyse with particular attention to the spatio-temporal distribution of nanoflares.
At the same time, we treat the thermodynamic response of the plasma self-consistently, and study the evolving temperature profiles.
Avalanches successfully propagate in curved arcades and appear capable of maintaining a hot corona with realistic temperatures and densities in heated loops.
One novelty of interest lies in `campfire'-like events, with simultaneous reconnection events at disjoint sites along coronal strands, akin to recent results from Solar Orbiter.

How to cite: Reid, J., Johnston, C. D., Threlfall, J., and Hood, A. W.: Self-consistent modelling of nanoflares: generation of heating and thermodynamic response in 3D MHD, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3475, https://doi.org/10.5194/egusphere-egu23-3475, 2023.

Magnetic flux ropes are bundles of twisted magnetic field lines produced by the internal flowing electric currents, which are regarded as one of the basic and pivot structures in solar and space physics. Statistics showed that about 90% of the erupting filaments are supported by flux ropes, implying that the majority of solar eruptions are driven by flux ropes. Moreover, the post-eruption flux ropes in interplanetary space, called interplanetary magnetic clouds, are the major drivers of geomagnetic storms. As such, a numerical model that is capable of capturing the whole process of the flux rope from its birth to its death or eruption is certainly crucial for predicting adverse space weather events. Recently, we develop a data-driven model combined with the observed vector magnetic field and velocity field, which reproduces the formation and confined eruption of an observed flux rope. We find that the photospheric shearing and converging plasma flows play a critical role in the flux rope formation, and the magnetic configuration is analogous to the “tether-cutting”  reconnection illustration. Regarding the confined eruption, we find that the deformation of the flux rope during the eruption causes an increase in downward tension force, which suppresses the ascendence of the flux rope. This finding might shed light on why many large-angle rotation events are always confined and torus unstable.

How to cite: Guo, J., Ni, Y., Guo, Y., Xia, C., Chen, P., Poedts, S., and Schmieder, B.: Data-driven simulation of a magnetic flux rope in the heliosphere: from birth to death, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4394, https://doi.org/10.5194/egusphere-egu23-4394, 2023.

Spectroscopic observations of the solar atmosphere reveal regions of the solar corona that are enriched in the abundance of heavy element with low-first ionisation potential (examples of low ‘FIP’ i.e. with <10 eV are Fe, Mg) relative to photospheric abundances. This enhancement in the abundance of low-FIP elements by a factor of three or four, called the ‘FIP effect’, is still not well understood. Moreover enriched abundances of low-FIP elements are also observed in the slow solar wind, which could give us more insights on its origins. An inverse-FIP effect corresponding to a decreased abundance of low-FIP elements has been measured in the atmosphere of M-type stars.

Turbulent mixing of the chromosphere combined with the ponderomotive force caused by Alfvén waves propagating in these atmosphere could give a mechanism that might explain the FIP effect. Diffusive theories including the thermal force exerted on the ions due to a collision frequency gradient has also a role to play on minor ion extraction from the chromosphere.  Our goal is to study and compare these effects using  ISAM, a new 1D 16 moments multi-fluid model taking into account collisional effects of the different heavy ions. In this work we use profiles from 3 different solar wind types simulated using ISAM in which we propagate Alfvén waves with a Shell Model of Alfvén-wave turbulence. We then compare the FIP bias obtained from these 3 types of wind.

This work has been funded by the ERC SLOWS SOURCE − DLV − 819189

How to cite: Lomazzi, P., Réville, V., Rouillard, A., and Petit, P.: Studying ionic composition in open field regions using a 16 moments multi-species fluid model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7415, https://doi.org/10.5194/egusphere-egu23-7415, 2023.

Three-dimensional (3-d) magnetohydrodynamics (MHD) modeling is a key method for studying the interplanetary solar wind. In this article, In this paper, we introduce a new 3-d MHD solar wind model driven by the self-consistent boundary condition obtained from multiple observations and Artificial Neural Network (ANN) machine learning technique. At the inner boundary, the magnetic field is derived using the magnetogram and potential field source surface extrapolation; the electron density is derived from the polarized brightness (pB) observations, the velocity can be deduced by an ANN using both the magnetogram and pB observations, and the temperature is derived from the magnetic field and electron density by a self-consistent method. Then, the 3-d interplanetary solar wind from CR2057 to CR2062 are modeled by the new model with the self-consistent boundary conditions. The modeling results present various observational characteristics at different latitudes, and are in good agreement with both the OMNI and Ulysses observations.

How to cite: Shen, F., Yang, Y., and Feng, X.: 3D MHD Modeling of Interplanetary Solar Wind Using Self-Consistent Boundary Condition Obtained from Multiple Observations and Machine Learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10143, https://doi.org/10.5194/egusphere-egu23-10143, 2023.

We perform a data-constrained simulation with the zero-β assumption to study the mechanisms of strong rotation and failed eruption of a filament in active region 11474 on 2012 May 5 observed by Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The initial magnetic field is provided by nonlinear force-free field extrapolation, which is reconstructed by the regularized Biot-Savart laws and magnetofrictional method. Our simulation reproduces most observational features very well, e.g., the filament large-angle rotation of about 130°, the confined eruption and the flare ribbons, allowing us to analyze the underlying physical processes behind observations. We discover two flux ropes in the sigmoid system, an upper flux rope (MFR1) and a lower flux rope (MFR2), which correspond to the filament and hot channel in observations, respectively. Both flux ropes undergo confined eruptions. MFR2 grows by tether-cutting reconnection during the eruption. The rotation of MFR1 is related to the shear-field component along the axis. Moreover, we find that the magnetic tension force is the cause of the confined eruption of MFR1. We also suggest that the mutual interaction between MFR1 and MFR2 contributes to the large-angle rotation and the eruption failure. In addition, we calculate the temporal evolution of the twist and writhe of MFR1, which may be a hint of probably existing reversal rotation.

How to cite: Zhang, X., Guo, J., Guo, Y., Ding, M., and Keppens, R.: Rotation and Confined Eruption of a Double Flux-Rope System, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10557, https://doi.org/10.5194/egusphere-egu23-10557, 2023.

According to the standard scenario of plasma emission, the escaping radiations are generated from the nonlinear development of the kinetic bump-on-tail instability, by a single beam of energetic electrons interacting with an overdense plasma. The primarily-excited beam-Langmuir mode and its further scattering over ion-related disturbances are suggested to be critical to the radiation process. Yet, non-beam distributions of energetic electrons, such as the ring (or ring-beam), DGH, loss-cone, horseshoe-like, etc., also exist broadly in space and astrophysical plasmas. They may drive wave modes distinct from those in the beam-plasma system. The corresponding radiation process could be distinct from that described by the standard scenario. To clarify this, we conducted particle-in-cell simulations to investigate the nonlinear response of an overdense plasma disturbed by energetic electrons of velocity distributions (VDs) changing from beam-like to ring-like. Efficient excitations of both the fundamental (F) and harmonic (H) plasma emissions are found for all the VDs investigated here, yet the kinetic instability, the wave modes excited, and the F/H radiation process are different. Details of these differences will be overviewed in this report.

How to cite: Chen, Y.: Coherent Radiation in Overdense Plasmas Interacting with Energetic Electrons of Different Velocity Distributions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17301, https://doi.org/10.5194/egusphere-egu23-17301, 2023.

A collisionless shock is a self-organized system, the main task of which is fast and stable transfer of the conserved quantities, that is, mass, momentum, and energy, from one side, upstream, to the other side, downstream, while adding entropy. ”Fast” means that the transfer occurs at the scales
much smaller than the MHD scales. ”Stable” means that there are not disruptions of substantial changes on average, except those which are caused
by variations of ambient conditions. In this approach the developing shock structure is the one which ensures this transfer. This means, that if the
transfer stability is not possible without an overshoot, an overshoot has to be formed. If it is not possible without rippling, rippling will develop. Since
ions are the main carriers of these conserved quantities, it is ions which are responsible for developing the structure and it is ions which have to
most strongly affected by it. In particular, we show that overshoot plays an important role regulating ion reflection so that the shock becomes stable.

How to cite: Gedalin, M.: Collisionless shock as a self-organized system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17375, https://doi.org/10.5194/egusphere-egu23-17375, 2023.

Solar radio zebras detected as fine structures of Type IV radio bursts help to diagnose the coronal plasma at kinetic micro-scales. One of the models of the radio zebras is the electron-cyclotron maser instability based on a double plasma resonance at gyro-harmonics of the electron cyclotron frequency when ω_pe > ω_ce. Though the gyro-harmonic numbers estimated for zebra observations are very high, in some cases exceeding 100, it is still uncertain how the instability can grow and generate zebra stripes for them. To investigate the instability evolution, we studied its growth and saturation by utilizing analytical calculations and particle-in-cell simulations. We found that the growth rates and saturation energies as functions of the cyclotron-to-plasma frequency ratio form a profile that peaks approximately at the integer harmonics of the cyclotron frequency. Nonetheless, the peaks shift to lower frequencies with increasing the plasma loss-cone temperature, and they broaden and decrease with increasing the gyro-harmonic number. These results suggest that emissions for very high gyro-harmonic numbers should not be formed. Hence, to explain the detected high gyro-harmonic numbers of one hundred, we also investigated the growth rates as a function of the loss-cone angle and found that distributions with very  high loss-cone angles can interpret the observations. We proposed that such large loss-cone angles can be generated in magnetic loops with small magnetic field gradients or below an X-point of the magnetic reconnection. 

How to cite: Benáček, J. and Karlický, M.: Electron-cyclotron emission model of solar radio zebras with high gyro-harmonic numbers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17380, https://doi.org/10.5194/egusphere-egu23-17380, 2023.

We present the implementation of a coupling between EUropean Heliospheric FORcasting Information Asset (EUHFORIA) and improved Particle Acceleration and Transport in the Heliosphere (iPATH) models. In this work, we simulate the widespread solar energetic particle (SEP) event of 2020 November 29 and compare the simulated time-intensity profiles with measurements at Parker Solar Probe (PSP), the Solar Terrestrial Relations Observatory (STEREO)-A, SOlar and Heliospheric Observatory (SOHO), and Solar Orbiter (SolO). We examined the temporal evolution of shock parameters and particle fluxes during this event and we find that adopting a realistic solar wind background can significantly impact the expansion of the shock and, consequently, the shock parameters. Time-intensity profiles with an energetic storm particle event at PSP are well reproduced from the simulations. In addition, the simulated and observed time-intensity profiles of protons show a similar two-phase enhancement at STA. These results illustrate that modeling a shock using a realistic solar wind is crucial in determining the characteristics of SEP events. The decay phase of the modeled time-intensity profiles at Earth is in good agreement with the observations, indicating the importance of perpendicular diffusion in widespread SEP events. Taking into account the possible large curved magnetic field line connecting to SolO, the modeled time-intensity profiles show a good agreement with the observation. We suggest that the broadly distorted magnetic field lines, which are due to a stream interaction region, may be a key factor in understanding the observed SEPs at SolO.

How to cite: Ding, Z., Wijsen, N., Li, G., and Poedts, S.: Modeling the 2020 November 29 solar energetic particle event using EUHFORIA and iPATH models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7, https://doi.org/10.5194/egusphere-egu23-7, 2023.

Solar Energetic electron (SEE) events are the most common solar particle acceleration phenomenon detected in situ in the interplanetary medium and the energy spectrum of SEE events carries crucial information on the acceleration and/or transport processes of SEEs. In our research, we investigate the peak flux energy spectrum of 458 SEE events with a clear velocity dispersion detected at energies from ≤ 4.2 keV to ≥ 108 keV by Wind/3DP from 1994 December through 2019 December, utilizing a pan-spectrum fitting method. According to the fitted spectral parameters, these 458 events are self-consistently classified into five spectral shapes: 304 DDPL events, 32 UDPL events, 23 SPL events, 44 ER events and 55 LP events. The DDPL events can be further divided in to two types: 231 E_B≥20 keV DDPL events and 73 E_B<20 keV DDPL events, since the distribution of break energy E_B exhibits a primary peak around 60 keV and a secondary peak around 7 keV, separated by a dip at ~20 keV. The E_B≥20 keV (E_B<20 keV) DDPL events exhibit a power-law spectral index of 2.0^+0.2_-0.2(2.1^+0.3_-0.3) (values shown in a form of A^+B_-C means the median value with the first and the third quartiles) at energies below E_B=5.6^+2.3_-2.4 keV (60⁺²³_-12 keV) and index of 3.3^+0.5_-0.3 (3.9^+0.6_-0.7) at energies above.The UDPL events have a spectral index of 3.0^+0.3_-0.3 at energies below E_B=5.1^+4.2_-1.8 keV and index of 2.2^+0.2_-0.3 at energies above. The SPL events shows a spectral index of 2.8^+0.5_-0.2. The ER events exhibit a spectral index 1.9^+0.3_-0.3 at energies below E_c=30⁺¹⁹_-10 keV. The six spectrum types also behave differently in the relationship between spectral parameters and in solar cycle variations. Furthermore, propagation effects in the IPM from the Sun to 1 AU appear to have no obvious influence on the spectral shape of most SEE events. These results suggest that the formation of SEE events can involve complex processes/sources.

How to cite: Wang, W., Wang, L., Liu, Z., Krucker, S., and Wimmer-Schweingruber, R. F.: Energy Spectrum of Solar Energetic Electron Events Over 25 Years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1741, https://doi.org/10.5194/egusphere-egu23-1741, 2023.

We perform a statistical study of the relations between the properties of solar energetic electron (SEE) events measured by the MESSENGER mission from 2010 to 2015 and the parameters of the respective parent solar activity phenomena to identify the potential correlations between them. During the time of analysis MESSENGER heliocentric distance varied between 0.31 and 0.47 au.

The main conclusion of the study is as follows. For this particular sample of events, with a majority of SEE events being widespread in heliolongitude and displaying relativistic electron intensity enhancements, a shock-related acceleration mechanism might be relevant in the acceleration of near-relativistic electrons. This conclusion is mainly based on three results. (1) The high and significant correlation found between the SEE peak intensities and the shock speed. (2) The ∼4 orders of magnitude in the SEE peak intensities for the same CME-driven shock speed that might be related to the presence of supra-thermal seed population that made local shock acceleration more efficient. (3) The asymmetry to the east of the range of connection angles (CAs) for which the SEE events present higher peak intensities and higher correlations with the solar activity, which might be related to the evolution of the magnetic field connection to the shock front. We note that the CA is defined as the angular distance between the footpoint of the magnetic field connecting to the spacecraft and the longitude of the source region.

How to cite: Rodríguez-García, L., Balmaceda, L., Gómez-Herrero, R., Kouloumvakos, A., Dresing, N., Lario, D., Zouganelis, Y., Fedeli, A., Espinosa Lara, F., Cernuda, I., Ho, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Solar activity relations in energetic electron events measured by the MESSENGER mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2518, https://doi.org/10.5194/egusphere-egu23-2518, 2023.

Most of the energetic particles observed in the heliosphere are accelerated from a few keV up to MeV by shock fronts which are associated with the transit of coronal mass ejections (CMEs). The study of energetic storm particle events (ESP) can be very helpful for the investigation of the acceleration processes of particles at the shocks. We considered two ESP events occurring 6-7 September, 2017. The data used to study kinetic energy spectra are proton flux enhancements provided by WIND and ACE spacecraft that are both at the Lagrangian point L1, close to 1 AU along the Sun-Earth direction. The energy ranges are from 70 keV to 70 MeV and from 40 keV to 4.8 MeV, respectively. In order to broaden the range of the analyzed energies, we combine these data with the proton fluxes from SoHO spacecraft, also located at L1, which detects particles with energies from 1.3 MeV to 130 MeV. We used the Weibull functional form, the double power law and the Ellison-Ramaty form to fit the observed spectra. The implications of the obtained results for particle acceleration are discussed, taking also into account the properties of the shocks and of the magnetic turbulence in their surroundings.

“This research has been carried out in the framework of the CAESAR project, supported by the Italian Space Agency and the National Institute of Astrophysics through the ASI-INAF n. 2020-35-HH.0 agreement for the development of the ASPIS prototype of scientific data centre for Space Weather.”

How to cite: Chiappetta, F., Laurenza, M., Lepreti, F., Benella, S., and Consolini, G.: Analysis of the Energetic Storm Particle events of 6-7 September 2017, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4398, https://doi.org/10.5194/egusphere-egu23-4398, 2023.

Radiation is one of the most important risks to deep space exploration programs such as manned missions to the Moon and Mars. In preparation for such programs, it requires a thorough understanding of interplanetary space weather conditions and a timely forecast of their potential effects as a baseline for the development of mitigation strategies. 

Radiation damage in space comes mainly from two sources, Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs). In particular, intense SEP events could result in very high doses in a short time period that may exceed the threshold to induce deterministic radiation effects and to result in severe damages to humans and equipment leading to the failure of the entire mission. SEP events with radiation hazards, despite of being rather infrequent and sporadic, are however very difficult to forecast and remain as a major challenge for space weather studies in preparation for future deep space and Mars missions.

Specifically speaking, the SEP radiation reaching an astronaut on a Mars may be completely different from of that detected at (or predicted for) Earth’s vicinity, including the SEP onset time, spectra evolution, radiation intensity etc. This is due to (1) the different location of Mars and connectivity to the acceleration source which allow it to have difference access to the SEP population, and (2) the different planetary environment which modifies the energy and composition of the particles due to the interactions of primary particles with the atmosphere/regolith and the generation of secondaries. The synergistic analysis and modeling of these two processes are particularly important to understand and eventually forecast SEPs and their radiation effects on Mars in preparation for mitigating their potential hazardous effects.  We also emphasize the utmost importance of utilizing multi-spacecraft particle measurements at Mars and also other heliospheric locations to better understand such extreme events and their radiation effects for future deep space explorers.

How to cite: Guo, J.: The Impact of Solar Energetic Particles at Mars’ radiation environment: A synergistic approach combining measurements and Modeling efforts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5292, https://doi.org/10.5194/egusphere-egu23-5292, 2023.

¹⁰Be is a cosmogenic isotope continuously produced in the Earth’s atmosphere by galactic cosmic rays (GCRs) and sporadically by solar energetic particles (SEPs). The long-living isotope, as measured in polar ice cores, typically with an annual resolution, serves as a proxy for long-term cosmic-ray variability, whose signal can, however, be distorted by atmospheric transport and deposition that need to be properly modelled. Atmospheric transport of ¹⁰Be depends on production, atmospheric circulation, and local orography. For an accurate physical description of the isotope's transport and deposition, we use the chemical climate model (CCM) SOCOL-AER2-BE. In combination with the production model CRAC, our model was verified using real measurements of beryllium in ice cores for Antarctic and Greenland locations. The model results agree with the measurements at the absolute level, implying that the production, decay, and lateral deposition are correctly reproduced. However, the exact time variability is not always well reproduced, particularly for the Greenland shore sites implying significant regional effects. Potentially, extreme SPEs that are orders of magnitude stronger than those observed during the recent decades can be recorded in cosmogenic isotope data, and a proper model is needed to study them. Here we present a model of the production and transport of ¹⁰Be for a major solar energetic particle event (GLE 69) and analyze the geographical pattern of the beryllium concentration.

How to cite: Golubenko, K., Rozanov, E., Kovaltsov, G., Baroni, M., and Usoskin, I.: Modelling of atmospheric transport of SEP-induced cosmogenic 10Be  using CCM SOCOL-AER2-BE, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7171, https://doi.org/10.5194/egusphere-egu23-7171, 2023.

During major solar energetic particle events, radiation dose rates in Earth's atmosphere at aviation altitudes can increase by orders of magnitude relative to dose rates during quiet times in events known as Ground-Level Enhancements (GLEs). In the case of events of a scale such that they occur once every few decades, radiation dose rates could become high enough that they pose a threat to aircraft crew and electronics. It is not currently possible to predict when such an event will occur, and existing software systems are only capable of nowcasting the current atmospheric radiation dose rates using real-time data sources. However, while it is not possible to forecast when a major event will occur, it may be possible to generate forecasts for radiation dose rates once an event has been registered to have begun. The ability to provide forecasts for dose rates once a GLE has started would be vital for airlines and for pilots in any future where aircraft might be rerouted to avoid regions of high radiation, as pilots need to be able to know not just their current radiation dose rates but radiation dose rates at possible locations where their plane might be in say half an hour's time. We report on the development of a software system to do this. This 'in-progress' radiation dose rate forecasting system will be developed by integrating the FOrecasting Relativistic particles during GLE Events (FORGE) system being developed at the University of Central Lancashire with an anisotropic extension to the Models for Atmospheric Ionising Radiation Effects+ (MAIRE+) system being developed at the University of Surrey. We report on the development of both of these systems and their integration.

How to cite: Davis, C., Waterfall, C., Lei, F., Dalla, S., Ryden, K., Clewer, B., and Dyer, C.: Development of an In-Progress Forecasting Model to Forecast Radiation Dose Rates Once a Ground-Level Enchancement has Begun, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7905, https://doi.org/10.5194/egusphere-egu23-7905, 2023.

How to cite: Mowbray, K. and Neukirch, T.: Particle Energisation in a 3D Collapsing Magnetic Trap Model With a Braking Jet , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8936, https://doi.org/10.5194/egusphere-egu23-8936, 2023.

A joint analysis approach is used to study flare signatures both in the low and higher corona. STIX, AIA and LOFAR data provide an extensive picture about different aspects of flare characteristics. Recent data by the STIX instrument complement the picture of accelerated electrons, which propagate along magnetic field lines towards the Sun. These observations are linked to the LOFAR data, which contain information about the elctrons propagating away from the Sun through the corona above the active region. Although, the active region and its thermal evolution (Differential Emission Measure (DEM) reconstruction of AIA data), flare accelerated electrons and their radio traces (LOFAR, STIX) are in principal all associated with the energy release during the flare process, they are often studied seperatly. Hence, the investigation of possible relations is part of this project. Solar magnetic fields as a binding element between low and high corona, accelerated electrons and heated flare loops are included in the analysis via a Potential Field Source Surface (PFSS) model.

How to cite: Bröse, M. and Vocks, C.: Flare-accelerated electrons and their traces in the solar corona observed by space- and ground-based instruments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9582, https://doi.org/10.5194/egusphere-egu23-9582, 2023.

The first three years of Solar Orbiter operations have enabled robust sampling of the intensity and composition of suprathermal particles within the inner heliosphere. This includes a multitude of observations of suprathermal ions associated with Corotating Interaction Regions (CIRs), with corresponding observations at 1 au with measurements from the Ultra-Low-Energy Isotope Spectrometer (ULEIS) on the Advanced Composition Explorer (ACE) mission and the Suprathermal Ion Telescope (SIT) on the Solar-Terrestrial Relations Observatory-Ahead (STEREO-A) spacecraft. Comparing observations between these spacecraft allows for a statistical view of the radial variations of CIR-associated suprathermal particles by composition in the inner heliosphere, allowing for greater insight into energetic particle transport within the inner heliosphere. This study expands on early results from Solar Orbiter and ACE to now encompass the first three years of Solar Orbiter operations, as well as include STEREO-A measurements. Comparisons to historical studies of CIR-associated energetic protons are also expanded in the survey of CIR-associated suprathermal particles from Solar Orbiter, ACE, and STEREO-A.

How to cite: Allen, R., Ho, G., Mason, G., Kouloumvakos, A., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Radial Variation of Suprathermal Particles Associated with Corotating Interaction Regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10509, https://doi.org/10.5194/egusphere-egu23-10509, 2023.

The energy spectrum of solar energetic electron (SEE) events carries crucial information on the origin/acceleration of energetic electrons at the Sun. Using  the Wind 3DP electron measurements at ~1 to 200 keV during 1995-2019, we select 11 good SEE events with a bump-like break in the peak flux vs. energy spectrum, different from the typical SEE events with a double-power-law spectrum. For the selected 11 events, the background-subtracted electron peak flux versus energy spectrum fits well to two functions: the sum of a single-power-law and a Gaussian function (spectral function #1) and the product of a single-power-law and the natural exponential form of a Gaussian function (spectral function #2). For the spectral function #1 (#2), on average, the fitted spectral index is 2.6±0.4 (2.7±0.6), significantly larger than the low-energy power-law index of typical SEE events, while the fitted center energy of spectral bump is 24±7 keV (75±38 keV) and the ratio of bump width and center is 2.0±0.7 (3.4±2.8). Among these 11 events, respectively, ~78%, ~89%, ~90%, 100% and ~55% are associated with GOES SXR flares, RHESSI HXR flares, west-limb CMEs, type III radio bursts and type II  radio bursts. Thus, these bump events have a stronger association with flares, coronal mass ejections (CMEs) and type II radio bursts, compared to the typical SEE events. In addition, we find a positive correlation between the center energy of bump and the CME speed. Therefore, we come up with an acceleration picture of these bump SEE events: the power-law portion is probably accelerated by flares with the acceleration efficiency larger at lower energies, while the bump portion is likely accelerated in CME-related processes with the acceleration efficiency increasing with the CME speed.

How to cite: Li, W., Wang, L., and Wang, W.: Solar Energetic Electron Events with a Spectral Bump, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11362, https://doi.org/10.5194/egusphere-egu23-11362, 2023.

Compositional NOx changes caused by energetic electron precipitation (EEP) at a specific altitude are called the EEP direct effect. Changes co-dependent on vertical transport are referred to as the EEP indirect effect. The relative importance of EEP’s direct and indirect effect on NO and its subsequent impact on ozone and dynamic changes remain unresolved. The challenges are partly due to inadequate particle measurement and the relative scarcity of NO observations over the polar MLT region. Moreover, lower production rates in the mesosphere make it challenging to determine EEP’s direct impact on NO since small in-situ enhancements cannot be easily distinguished from the descending NO-rich air masses in the winter hemisphere. In this study, the uncertainty of the EEP observations is bypassed by exclusively identifying events applying NO-observations from the SOFIE instrument on board the AIM satellite. SOFIE daily averaged data from 2007 to 2014 is used to create a climatology based on the mean of the lower half of the data (lower 50 percentile mean). A direct EEP-produced NO-event at 90 km (“90km-event”) is identified when the NO density surpasses the climatology by 100%. If the NO density exceeds 25% above the climatology at 80, 70, 60, and 50 km, the event qualifies as a “50km-event”. By contrasting the 90km and 50km events, the characteristics of the solar wind and geomagnetic indices, as well as observed electron fluxes from POES, are studied. The goal is to unravel when EEP can produce NO directly in the upper stratosphere. The result will contribute to developing a parameterization of EEP from the radiation belt that includes both the direct and indirect impact of EEP to decipher the total EEP effect on the ozone and atmospheric dynamics.

How to cite: Salice, J., Nesse, H., Partamies, N., Kilpua, E., Kavanagh, A., Babu, E., and Smith-Johnsen, C.: When are energetic electrons producing NO directly in the upper stratosphere?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12330, https://doi.org/10.5194/egusphere-egu23-12330, 2023.

A novel ionisation detector, previously deployed on meteorological radiosonde flights, has demonstrated responsivity to X-rays and gamma radiation, and additionally, is thought to be sensitive to ionising radiation from cosmic rays. The PiN detector, composed of a 1x1x0.8 cm³ CsI(Tl) microscintillator coupled to a PiN photodiode, was deployed on the NRP Sagres sailing vessel on a cruise in the Atlantic between Portugal and the Azores in 2021. The instrument can determine both the count rate and energy of incoming ionising radiation particles.

The instrument was operational during the voyage in November 2021 when a coronal mass ejection event induced a sudden decrease in the observed cosmic ray intensity, known as a Forbush decrease. We present data recorded by the ionisation detector during this period, to characterise the instrument’s ability to detect cosmic ray events, and we compare the performance with neutron monitoring stations Oulu in Finland, and Dourbes in Belgium. As the PiN detector provides spectral and count rate data, it is possible to group events by their energy, and investigate the count rates of specific energy regimes. This approach is useful as many sources – including high and low energy ionising radiation from cosmic rays – contribute to the background energy spectrum. As a result, more meaningful comparisons and relationships can be established with the neutron monitoring stations.

How to cite: Tabbett, J., Aplin, K., and Barbosa, S.: Witnessing a Forbush Decrease with a Microscintillator Ionisation Detector over the Atlantic Ocean, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13801, https://doi.org/10.5194/egusphere-egu23-13801, 2023.

The main goal of the radiation monitor RADEM flying onboard the ESA JUICE mission is to provide continuous information on particle fluxes and their energy spectra. The monitor measures electrons up to 40 MeV and protons up to 250 MeV. Such a range of energies detected by RADEM enables covering the most hazardous regimes in terms of radiation damage. Spectroscopic information on particle energies is provided using eight quasi-logarithmic energy bins. RADEM has also a dedicated heavy-ion detector designed to measure a variety of heavy ion species with their LET between 0.1 and 10 MeV/cm/mg^-1. Moreover, the monitor contains an additional detector sensitive to the direction of incoming radiation. It expands the instrument's angular coverage up to 35% of the sky. Apart from its spectroscopic and angular distribution functions, RADEM will continuously provide values of the radiation dose deposited by each particle species. Its telemetry data will be stored in the data center for the JUICE mission operated by the European Space Astronomy Centre. After preprocessing the higher-level data will become available to the JUICE scientific team. RADEM will be switched on shortly after the JUICE launch planned for April 2023 and after a short commissioning phase will start its nominal operation. Apart from regular and short tuning and calibration periods, it will remain operating for the rest of the mission i.e. almost 10 years. While its primary purpose is to monitor the mission levels for safety concerns of the spacecraft and its scientific payload, its measurements open a unique opportunity for conducting real-time, continuous observations during its full cruise to Jupiter. RADEM will study all aspects of the radiation phenomena characteristic to the Earth and Solar System. Correlations with other instruments will allow for advanced observations of particle event propagation and a better understanding of processes related to the dynamics of particle environments including their links with solar activity and magnetic fields across the solar system. In particular, during its first two years of the cruise to Jupiter, RADEM will precisely map the radiation environment between Venus and Mars, providing uninterrupted time-resolved spectroscopy and dosimetry data from Solar Energetic Particles and Cosmic Rays.

How to cite: Hajdas, W., Goncalves, P., Pinto, M., Galli, A., and Witasse, O.: Monitoring of Solar Energetic Particles and Cosmic Rays with the RADEM instrument onboard the ESA JUICE mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14711, https://doi.org/10.5194/egusphere-egu23-14711, 2023.

Shock waves propagating in the interplanetary space are efficient sources of energetic particles. In situ spacecraft observations, especially particle fluxes which can be used to obtain energy spectra, provide very useful data for the investigation of the acceleration mechanisms occurring at shocks. In this work we analyse the kinetic energy spectra of several proton flux enhancements associated with energetic storm particle (ESP) events observed by various spacecraft. ESP events occurring both in association with and in absence of Solar Energetic Particles (SEPs) are considered. Moreover, ESP events associated both with quasi-perpendicular and quasi parallel shocks are investigated.  Different functional forms (i.e. Weibull function, double power law, and Ellison-Ramaty) are used to fit the observed spectra and the obtained results are discussed in relation to the shock properties and to the magnetic turbulence and intermittency in the upstream and downstream regions. More specifically, the properties of magnetic turbulence and intermittency are analysed by calculating power spectral densities and structure functions of the fluctuations of the magnetic field components and the implications for particle acceleration are examined.

This research has been carried out in the framework of the CAESAR project, supported by the Italian Space Agency and the National Institute of Astrophysics through the ASI-INAF n. 2020-35-HH.0 agreement for the development of the ASPIS prototype of scientific data centre for Space Weather.

How to cite: Lepreti, F., Chiappetta, F., Laurenza, M., Benella, S., and Consolini, G.: Proton energy spectra of energetic storm particle events and their relation with magnetic turbulence and intermittency nearby interplanetary shocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15517, https://doi.org/10.5194/egusphere-egu23-15517, 2023.

The large-scale magnetic structure of interplanetary coronal mass ejections (ICMEs) has been shown to cause temporary decreases in the galactic cosmic ray (GCR) flux measured in situ by spacecraft, known as Forbush decreases (Fds). In some ICMEs, the magnetic ejecta exhibits a magnetic flux rope structure; the strong magnetic field strength and closed field line geometry of such ICME magnetic flux ropes has been proposed to act as a shield to GCR transport. However, as ICMEs propagate, they undergo many processes including interactions and magnetic reconnection with the interplanetary magnetic field (IMF) in large-scale solar wind structures and other solar transients. In this study, we investigate how ICME interaction and reconnection during propagation affects Fd size, shape, and duration. We hypothesize that the alteration of the ICME magnetic topology due to reconnection (specifically the opening of the closed magnetic field configuration in the ICME flux rope) will have a strong effect on the ICME’s ability to modulate GCRs. To test this hypothesis, we compare the Fds of ICMEs that likely underwent reconnection during propagation with ones that likely did not.

To this end, we identify ICMEs that exhibited open magnetic field line topologies (i.e., ones that likely underwent reconnection) and we compare their effects on GCRs with those of ICMEs that exhibited closed topologies (both ends connected to the Sun). We use magnetic field, solar wind plasma, and suprathermal electron pitch angle distribution data at ACE and Wind to select the ICMEs. Furthermore, we use data by the SOPO and McMurdo neutron monitors at Earth to investigate how the magnetic structure of the ICME ejecta modulates the GCRs by comparing the resulting Fds for the selected ICMEs. The results of our study yield new insights into how the modulation of GCRs is affected by ICME evolution and interaction during propagation and whether reconnection of the ICME flux rope weakens its modulation of GCRs.

How to cite: Davies, E., Scolini, C., Winslow, R., and Jordan, A.: The effect of magnetic reconnection on ICME-related GCR modulation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15621, https://doi.org/10.5194/egusphere-egu23-15621, 2023.

The region separating the inner and outer radiation belt, typically devoid of energetic electrons, is termed the slot region. The outer edge of the slot region marks the equatorward edge of the energetic electron precipitation (EEP) originating from the outer radiation belt. Its varying location is strongly linked to the plasmasphere and geomagnetic activity. As such, geomagnetic indices are used to estimate the equatorward extent of the EEP region. There are, however, numerous reports where the energetic electrons cross these boundaries and fill the slot region, during which energetic electrons that can precipitate into the atmosphere long after the geomagnetic activity subsides. This is a missing source of energy input in current EEP estimates based on geomagnetic indices.

This study explores the occurrence rate, reformation, local time dependence, and energy deposition of slot region filling events. Medium energy electron measurements from the NOAA/POES over a full solar cycle from 2004 to 2014 are applied. We combine observations from the MEPED 0° and 90° detectors together with theory of pitch angle diffusion by wave-particle interaction to estimate the precipitating fluxes. To explore the energy dependent characteristics, each of the MEPED energy channels, > 43, >114, and >292 keV are evaluated independently. Finally, we investigate the potential EEP impact on the NO density utilizing seven years of Envisat MIPAS NO observations from 2005 to 2011.

How to cite: Nesse, H., Babu, E. M., Salice, J., and Funke, B.: Energetic Electron Precipitation during Slot Region Filling Events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16136, https://doi.org/10.5194/egusphere-egu23-16136, 2023.

Future expeditions into interplanetary space, and in particular to the Moon and Mars, will expose astronauts to very high levels of cosmic radiation, which are known due to years of research and instruments that have been sent to space. It is, however, a limitation in understanding the risks of this radiation for the human body due to difficulties in simulating the complex space environment on Earth or complex human phantom and the inability to extrapolate human clinical outcomes based on animal models or simulation results. 
As human spaceflight continues on its path to success, we need to develop appropriate and effective mitigation strategies for future missions to improve our understanding of the space radiation risk by identifying the constraints of radiation research on the Earth and finding possible solutions based on the existing technologies to be closer to the reality as much as possible and better understand human physiology in space.  
As part of this paper, we have identified several factors that hinder our understanding of radiation risks for human crews and have identified ways to cope with these restrictions for a better understanding and preparation for human spaceflights in the future.

How to cite: Khaksarighiri, S., Wimmer-Schweingruber, R., Guo, J., Zeitlin, C., Berger, T., and Matthiä, D.: Risks of space radiation exposure to exploration astronauts: limitations in predictions based on the ground experiments and possible solutions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16177, https://doi.org/10.5194/egusphere-egu23-16177, 2023.

The interaction between interplanetary (IP) shocks and solar wind has been studied for the understanding of energy dissipation mechanisms and the properties of turbulence (e.g., cross helicity, residual energy, proton temperature anisotropy, magnetic compressibility, etc.) within collisionless plasmas. Compared to the study of the interaction with fast shocks, less attention has been directed to the interaction with other types of IP shocks including slow mode shocks (i.e., fast forward, fast reverse, slow forward and slow reverse). We analyze IP shocks observed by the Wind spacecraft from 1995 to 2021. Spectral indices in the ion inertial and kinetic ranges for the upstream and downstream magnetic field fluctuations are estimated by continuous wavelet transform. The changes of the plasma turbulence properties and the distributions of characteristic proton length scales are presented. We preliminarily found that spectral indices in both inertial and kinetic ranges and the distributions of characteristic proton length scales are statistically conserved across the investigated shocks. Mechanisms associated with the energy dissipation can be seen unaffected by shock. Other turbulence properties—cross helicity, residual energy and proton temperature anisotropy—evolve without a significant modification as well.

How to cite: Park, B., Pitňa, A., Šafránková, J., Němeček, Z., Krupařová, O., and Krupař, V.: The change of properties of solar wind turbulence across different types of interplanetary shocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3207, https://doi.org/10.5194/egusphere-egu23-3207, 2023.

The contribution presents the first comprehensive statistical study of the evolution of both compressive and non-compressive magnetic field fluctuations in the inner heliosphere. Based on Parker Solar Probe and Solar Orbiter data in various distances from the Sun, we address the general trends and compare them with Wind observations near 1 AU. We analyze solar wind power spectra of magnetic field fluctuations in the inertial and kinetic ranges of frequencies. We found a systematic steepening of the spectrum in the inertial range with the spectral index of around –3/2 at closest approach to the Sun toward –5/3 at larger distances (above 0.4 AU), the spectrum of the magnetic field component perpendicular to the background field being steeper at all distances. In the kinetic range, spectral indices increase from –4.5 at closest PSP approach to –3 at ≈0.4 AU and this value remains constant toward 1 AU. We show that the radial profiles of spectral slopes, fluctuation amplitudes, spectral breaks and their mutual relation rapidly change near 0.4 AU.

How to cite: Safrankova, J., Němeček, Z., Němec, F., Verscharen, D., Přech, L., Horbury, T. S., and Bale, S. D.: Evolution of magnetic field fluctuations and their spectral properties within the heliosphere: Statistical approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3214, https://doi.org/10.5194/egusphere-egu23-3214, 2023.

Ion-acoustic waves are often observed in the solar wind along the Solar Orbiter’s orbit. These electrostatic waves are generated via ion-ion or current-driven instabilities below the local proton plasma frequency. Due to the Doppler shift, they are typically observed in the frequency range between the local electron and proton plasma frequency in the spacecraft frame. Ion-acoustic waves often accompany large-scale solar wind structures and play a role in the energy dissipation in the propagating solar wind. Time Domain Sampler (TDS) receiver, a part of the Radio and Plasma Waves (RPW) instrument, is sampling wave emissions at frequencies below 200 kHz almost continuously from the beginning of the mission. Almost three years of observations allow us to perform a detailed study of ion-acoustic waves in the solar wind under variable plasma conditions. The emission tends to be observed when proton density and temperature are highly perturbed. A detailed analysis of the proton velocity distribution and wave generation using solar wind data from a Proton and Alpha particle Sensor (PAS) of the Solar Wind Analyzer (SWA) is shown.

How to cite: Pisa, D., Soucek, J., Santolik, O., Formanek, T., Maksimovic, M., Chust, T., Khotyaintsev, Y., Kretzschmar, M., Owen, C., Louarn, P., and Fedorov, A.: A detailed analysis of ion-acoustic waves observed in the solar wind by the Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6538, https://doi.org/10.5194/egusphere-egu23-6538, 2023.