Content:

PS – Planetary & Solar System Sciences

PS1.1 – Open Session on Exoplanetary Research

EGU2020-7520 | Displays | PS1.1

Machine-learning inference of the interior structure of low-mass exoplanets

Philipp Baumeister, Sebastiano Padovan, Nicola Tosi, Grégoire Montavon, Nadine Nettelmann, Jasmine MacKenzie, and Mareike Godolt

We explore the application of machine-learning, based on mixture density neural networks (MDNs), to the interior characterization of low-mass exoplanets up to 25 Earth masses constrained by mass, radius, and fluid Love number k2. MDNs are a special subset of neural networks, able to predict the parameters of a Gaussian mixture distribution instead of single output values, which enables them to learn and approximate probability distributions. With a dataset of 900,000 synthetic planets, consisting of an iron-rich core, a silicate mantle, a high-pressure ice shell, and a gaseous H/He envelope, we train an MDN using planetary mass and radius as inputs to the network. We show that the MDN is able to infer the distribution of possible thicknesses of each planetary layer from mass and radius of the planet. This approach obviates the time-consuming task of calculating such distributions with a dedicated set of forward models for each individual planet.

The fluid Love number k2 bears constraints on the mass distribution in the planets' interior and will be measured for an increasing number of exoplanets in the future. Adding k2 as an input to the MDN significantly decreases the degeneracy of possible interior structures.

How to cite: Baumeister, P., Padovan, S., Tosi, N., Montavon, G., Nettelmann, N., MacKenzie, J., and Godolt, M.: Machine-learning inference of the interior structure of low-mass exoplanets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7520, https://doi.org/10.5194/egusphere-egu2020-7520, 2020.

EGU2020-2471 | Displays | PS1.1

Climate bistability of rocky exoplanets

Antonello Provenzale, Giuseppe Murante, Giovanni Vladilo, Laura Silva, Erica Bisesi, Elisa Palazzi, and Jost von Hardenberg

Until about 600 million years ago, our planet experienced temporary snowball conditions, with continental and sea ices covering a large fraction of its surface. This points to a potential bistability of Earth’s climate, that can have at least two different (statistical) equilibrium states for the same external forcing (i.e., solar radiation). Here we explore the probability of finding bistable climates in rocky exoplanets, and consider the properties of planetary climates obtained by varying the semi-major orbital axis (thus, received stellar radiation), eccentricity and obliquity, and atmospheric pressure. To this goal, we use the Earth-like planet surface temperature model (ESTM), an extension of 1D Energy Balance Models developed to provide a numerically efficient climate estimator for parameter sensitivity studies and long climatic simulations. After verifying that the ESTM is able to reproduce Earth climate bistability, we identify the range of parameter space where climate bistability is detected. An intriguing result of the present work is that the planetary conditions that support climate bistability are remarkably similar to those required for the sustainance of complex, multicellular life on the planetary surface. The exploration of potential climate bistability proceeds with the case of a Earth-like planet partially covered by vegetation that generates a positive vegetation-albedo feedback, in the spirit of the Charney conceptual model. In this case, it is shown that the presence of this vegetation feedback can induce relevant changes in climate dynamics and alter the range of habitable conditions for the planet.

How to cite: Provenzale, A., Murante, G., Vladilo, G., Silva, L., Bisesi, E., Palazzi, E., and von Hardenberg, J.: Climate bistability of rocky exoplanets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2471, https://doi.org/10.5194/egusphere-egu2020-2471, 2020.

EGU2020-12792 | Displays | PS1.1

Stellar Proton Events and Exoplanetary Habitability

Dimitra Atri

Superflares of energies up to 1038 ergs have been studied from Kepler and Gaia observations, and estimates of their energy and frequency on different types of stars is improving rapidly. Flares with energies up to 1035 ergs occur about once every 2000-3000 years on slow rotating stars like the Sun, but the occurrence rate is ∼ 100 times higher for younger, faster rotating stars of the same class. More than a dozen potentially habitable planets, like Proxima Centauri b and TRAPPIST-1 e, are in close-in configurations and their proximity to the host star makes them highly sensitive to stellar activity. Episodic events such as flares have the potential to cause severe damage to close-in planets, adversely impacting their habitability. Stellar Energetic Particles (SEPs) emanating from Stellar Proton Events (SPEs) cause atmospheric damage (erosion and photochemical changes), and produce secondary particles, which in turn results in enhanced radiation dosage on planetary surfaces. Taking particle spectra from 70 major solar events (observed between 1956 and 2012) as proxy, we use the GEANT4 Monte Carlo model to simulate SPE interactions with exoplanetary atmospheres. We have demonstrated that radiation dose varies significantly with charged particle spectra and an event of a given fluence can have a drastically different effect depending on the spectrum. Our results show that radiation dose can vary by about five orders of magnitude for a given fluence. In terms of shielding, we found that atmospheric depth is a major factor in determining radiation dose on the planetary surface. Radiation dose is reduced by three orders of magnitude corresponding to an increase in the atmospheric depth by an order of magnitude. We found that the planetary magnetic field is an important but a less significant factor compared to atmospheric depth. The dose is reduced by a factor of about thirty corresponding to an increase in the magnetospheric strength by an order of magnitude.

How to cite: Atri, D.: Stellar Proton Events and Exoplanetary Habitability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12792, https://doi.org/10.5194/egusphere-egu2020-12792, 2020.

In the last two decades, the field of exoplanets has witnessed a tremendous creative surge. Research in exoplanets now encompasses a wide range of fields ranging from astrophysics to heliophysics and climate science. One of the primary objectives of studying exoplanets is to determine the criteria for habitability, and whether certain exoplanets meet these requirements. The classical definition of the Habitable Zone (HZ) is the region around a star where liquid water can exist on the planetary surface given sufficient atmospheric pressure. However, this definition largely ignores the impact of the stellar wind and stellar magnetic activity on the erosion of an exoplanet's atmosphere. Amongst the many factors that determine habitability, understanding the mechanisms of atmospheric loss is of paramount importance.

We will discuss the impact of exoplanetary space weather on the long-term climate evolution and habitability, which offers fresh insights concerning the habitability of exoplanets, especially those orbiting M-dwarfs, such as Proxima b and the TRAPPIST-1 planets. We will focus on a wide range of atmospheric compositions, ranging from exo-Venus candidates to Earth twins, as many factors remain unresolved at this stage. Future missions such as the James Webb Space Telescope (JWST) will play a crucial role in constraining the atmospheres of those exoplanets. For each of these cases, we will demonstrate the importance of the exoplanetary space weather on atmospheric ion loss and habitability.

How to cite: Dong, C.: Atmospheric escape from rocky M-dwarf planets orbiting within the habitable zone, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13528, https://doi.org/10.5194/egusphere-egu2020-13528, 2020.

EGU2020-16746 | Displays | PS1.1

Modeling the Atmospheric Contribution to the Interior Characterization of sub-Neptunes and its Effect on Habitability

Jasmine MacKenzie, Philipp Baumeister, Mareike Godolt, Nicola Tosi, Daria Kubyshkina, and Luca Fossati

As the number of confirmed exoplanets has increased, so too has the diversity in their physical parameters, namely their mass and radius. A common practice is to place these planets on a Mass-Radius diagram with various calculated density curves corresponding to some bulk composition. However, these lines don’t necessarily correspond to the structure of the planet found using interior models, particularly for low mass planets with masses less than 20 M and 4 R, which we call “sub-Neptunes.” Planets in this range can have highly degenerate solutions with no solar system analog, from so-called “ocean worlds” to small dense cores with extended primary composition atmospheres. We have created a model that is able to cover the range of solutions possible for sub-Neptunes, with various levels of complexity for both the interior and atmosphere. This includes both an isothermal and semi-grey atmosphere, along with a high-pressure solar composition envelope when atmospheric pressures exceed approximately 1000 bar. We then apply this model to known sub-Neptunes located in the extended habitable zone of their star using a hydrogen-helium dominated atmosphere. An atmospheric escape model is used to investigate the longevity of the atmosphere and its effect on the overall habitability of the planet.

How to cite: MacKenzie, J., Baumeister, P., Godolt, M., Tosi, N., Kubyshkina, D., and Fossati, L.: Modeling the Atmospheric Contribution to the Interior Characterization of sub-Neptunes and its Effect on Habitability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16746, https://doi.org/10.5194/egusphere-egu2020-16746, 2020.

PS1.2 – Space environments of unmagnetized or weakly magnetized solar system bodies and the effects of space weather on these systems

EGU2020-1508 | Displays | PS1.2

Observations of the Formation of Periodic Plasma Shocks from Fast Mode Waves

Lican Shan, Aimin Du, Bruce Tsurutani, Yasong Ge, Quanming Lu, Christian Mazelle, Can Huang, Karl-Heinz Glassmeier, and Pierre Henri

Collisionless plasma shocks (CPSs), forming when supersonic plasma streams encounter a magnetized obstacle, are invoked to explain the acceleration of ubiquitously energetic cosmic rays. It has long been theorized from magnetohydrodynamics, but not directly observed that the CPSs develop from the growth of small-amplitude, low-frequency plasma waves which excited by reflected ion beams from the obstacle. We present in situ observations of an entire formation sequence of the periodic plasma shocks by the MAVEN spacecraft’s magnetic field and particle instruments. The magnetometer first detected small-amplitude circularly polarized magnetosonic waves that further steepened and eventually evolved into periodic shocks. Moreover, differing from the traditional understanding, characterizations of the fast mode waves show that the free energy of the wave/shock generation is provided by newborn protons, and the increasing sunward proton fluxes provided persistent energy for wave steepening. The unusual evidence presents itself from the combination of two circumstances: radial-aligned (Sun-Mars) magnetic fields and Martian atmospheric atom (hydrogen) photoionization and solar wind pickup. These observations lead to the conclusion that newborn ions play a crucial role in the formation process of some CPSs in the astrophysical and space plasma.

How to cite: Shan, L., Du, A., Tsurutani, B., Ge, Y., Lu, Q., Mazelle, C., Huang, C., Glassmeier, K.-H., and Henri, P.: Observations of the Formation of Periodic Plasma Shocks from Fast Mode Waves, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1508, https://doi.org/10.5194/egusphere-egu2020-1508, 2020.

EGU2020-6871 | Displays | PS1.2

The Spacecraft Potential’s Influence on the FOV of Rosetta-ICA at Low Ion Energies

Sofia Bergman, Gabriella Stenberg Wieser, Martin Wieser, Fredrik Johansson, and Anders Eriksson

Low-energy ions play important roles in many processes in the environments around various bodies in the solar system. At comets, they are, for example, important for the understanding of the interaction of the cometary particles with the solar wind, including the formation of the diamagnetic cavity.

Unfortunately, spacecraft charging makes low-energy ions difficult to measure using in-situ techniques. The charged spacecraft surface will attract or repel the ions prior to detection, affecting both their trajectories and energy. The affected trajectories will change the effective FOV of the instrument. A negatively charged spacecraft will focus incoming positive ions, enlarging and distorting the FOV.

We model the low-energy FOV distortion of the Ion Composition Analyzer (ICA) on board Rosetta. ICA is an ion spectrometer measuring positive ions with an energy range of a few eV to 40 keV. Rosetta was commonly charged to a negative potential throughout the mission, and consequently the positive ions were accelerated towards the spacecraft before detection. This distorted the low-energy part of the data. We use the Spacecraft Plasma Interaction Software (SPIS) to simulate the environment around the spacecraft and backtrace particles from the instrument. We then compare the travel direction of the ions at detection and infinity, and draw conclusions about the resulting FOV distortion. We investigate the distortion for different spacecraft potentials and Debye lengths of the surrounding plasma.

The results show that the effective FOV of ICA is severely distorted at low energies, but the distortion varies between different viewing directions of the instrument. It is furthermore sensitive to changes in the Debye length and we observe a small non-linearity in the relation between FOV distortion, ion energy and spacecraft potential. Generally, the FOV is not significantly affected when the energy of the ions is above twice the spacecraft potential.

How to cite: Bergman, S., Stenberg Wieser, G., Wieser, M., Johansson, F., and Eriksson, A.: The Spacecraft Potential’s Influence on the FOV of Rosetta-ICA at Low Ion Energies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6871, https://doi.org/10.5194/egusphere-egu2020-6871, 2020.

EGU2020-8318 | Displays | PS1.2

Observations of low energy ions around the diamagnetic cavity at comet 67P

Gabriella Stenberg Wieser, Martin Wieser, Sofia Bergman, Elias Odelstad, Fredrik Johansson, and Hans Nilsson

We investigate the variations in low energy cometary ions around comet 67P. Detailed measurements of these ions were made possible by implementing a new instrumental mode of the ion mass spectrometer on the Rosetta spacecraft. The nominal time resolution was increased from 192 s to 4 s at the expense of the energy range and the field-of-view.

In this study we focus on ion observations made outside of, but in the vicinity of, the diamagnetic cavity. The ion dynamics here is clearly linked to variations of the magnetic field strength and properties of the electron velocity distribution, manifested by the spacecraft potential. Preliminary results show that the ion flux correlates with the changes of the spacecraft potential. The maximum ion flux is, however, observed about 20 seconds after a sudden decrease of the potential (corresponding to an increase in electron density if electron temperature is constant). We also find evidence of small ion temperature increases both when the spacecraft potential changes fast and at the time of maximum ion flux.

How to cite: Stenberg Wieser, G., Wieser, M., Bergman, S., Odelstad, E., Johansson, F., and Nilsson, H.: Observations of low energy ions around the diamagnetic cavity at comet 67P, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8318, https://doi.org/10.5194/egusphere-egu2020-8318, 2020.

EGU2020-10596 | Displays | PS1.2

Influence of foreshock electrons impact ionization on the amplitude of pickup protons generated waves at Mars

Christian Mazelle, Karim Meziane, Norberto Romanelli, David L. Mitchell, Suranga Ruhunisiri, Hadi Madanian, Ali Rahmati, Steven J. Schwartz, Jared R. Espley, Jasper S. Halekas, and Emmanuel Penou

Using MAVEN observations, we report variations of the amplitude of electromagnetic waves observed at the local proton cyclotron frequency upstream from the bow shock on short (plasma) time/length-scales: 1) a sharp sudden increase of the amplitude when crossing the electron foreshock boundary and 2) a decrease of this amplitude clearly correlated with the increasing distance from the shock along the magnetic field inside the foreshock without any simple relation to the planetary radial distance. These waves are excited by unstable ring-beam velocity distributions of newborn protons produced by ionization of exospheric hydrogen atoms. The amplitude of these waves is generally expected to depend only on different drivers including the observed large seasonality of the hydrogen exosphere, the EUV solar flux, the solar wind density and velocity or the IMF cone angle at different levels of importance. No noticeable wave amplitude change is expected when crossing the electron foreshock boundary and inside the pure electron foreshock. Surprisingly, we found that that these waves also display the two same aforementioned properties as the foreshock electrons fluxes at Mars though the wave origin is related to the ions only. We investigate the possibility that the extra free energy necessary to increase the wave amplitude could be due to supplementary ionization of hydrogen atoms by electron impact ionization inside the foreshock. Therefore, the electron foreshock also plays a role in the production of pickup protons which contribute to the planetary escape from high altitude.

How to cite: Mazelle, C., Meziane, K., Romanelli, N., Mitchell, D. L., Ruhunisiri, S., Madanian, H., Rahmati, A., Schwartz, S. J., Espley, J. R., Halekas, J. S., and Penou, E.: Influence of foreshock electrons impact ionization on the amplitude of pickup protons generated waves at Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10596, https://doi.org/10.5194/egusphere-egu2020-10596, 2020.

EGU2020-12241 | Displays | PS1.2

MAVEN Observations of Large-amplitude, Quasi-periodic Sawtooth-like Magnetic Field Oscillations Associated with Kelvin-Helmholtz Instability

Gangkai Poh, Jared Espley, Norberto Romanelli, Jacob Gruesbeck, and Gina DiBraccio

In this study, we present a preliminary analysis of large-amplitude sawtooth-like magnetic field oscillations observed by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft at Mars. Initial survey of these quasi-periodic magnetic field oscillations (with periods of ~3 – 4 minutes) shows distinct sawtooth-like magnetic field signatures with steep increase in BY of ~20 – 30 nT, followed by a gentle, but turbulent, return to background magnetic field values. The extrema in the BY component generally coincide with an extrema of opposite polarity in the BX component. Quasi-periodic magnetic field signatures can also be observed in the z-component of the magnetic field vector. Ion and electrons measurements shows corresponding increase in ions and electrons with energies greater than 30eV and 10 eV, respectively, during observations of these sawtooth-like oscillations, indicating some mixing of plasma. We interpret these observations as Kelvin-Helmholtz (KH) waves in the non-linear stages because the plasma and fields signatures are consistent with non-linear KH waves observed at Earth and other planetary environments. KH waves are developed as a result of flow shear-driven KH instability occurring between the boundary separating two moving fluids. In the non-linear stage of the KH instability, rolled-up KH vortex can developed along the boundary, allowing the mixing of plasma between the two plasma regions. Occurrence of KH waves had been observed at Venus’ ionopause and the induced magnetopause, contributing to loss of planetary ions in the form of plasma clouds. Earlier simulations and observational studies have also explored the possibility of non-linear KH instability occurring at Mars. We will discuss the conditions required for the development of KH instability, its growth rate and implications on mass loss at Mars. Comparison with simulations will also be conducted and discussed.

How to cite: Poh, G., Espley, J., Romanelli, N., Gruesbeck, J., and DiBraccio, G.: MAVEN Observations of Large-amplitude, Quasi-periodic Sawtooth-like Magnetic Field Oscillations Associated with Kelvin-Helmholtz Instability , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12241, https://doi.org/10.5194/egusphere-egu2020-12241, 2020.

EGU2020-12363 | Displays | PS1.2

Hemispheric Asymmetry in the Mars Summer Ionosphere at Various Solar Forcing Conditions

Marcin Pilinski, Laila Andersson, and Ed Thiemann

The MAVEN satellite has now made two Martian-years of ionosphere-thermosphere (I-T) observations enabling limited studies of seasonal changes in the upper atmosphere. Before examining the ionospheric dynamics associated with space weather, we wish to understand the climatological conditions of the system.  For example, previous studies have revealed the morning electron temperature overshoot as well as a close dependence between electron temperatures and neutral densities in the equatorial regions. In this presentation, we will examine differences in the northern and southern dayside ionosphere during the summer season of each hemisphere. The differences between these two cases will be contrasted with the seasonal dependence at the equator. Differences between the equatorial and polar regions are expected due to (A) differences in neutral scale heights, (B) differences in the solar zenith angle, and (C) the equilibration of I-T coupling due to differences in solar illumination.

In this work, we present a statistical analysis of MAVEN measurements comparing the north and south summer I-T. We find that when controlling for neutral pressure and latitude, the north and south plasma densities and temperatures are nearly identical below the demagnetization altitude (higher neutral pressures). Above the demagnetization altitude (lower neutral pressures), the southern hemisphere electron densities are higher than those in the northern hemisphere by ~100%. A significantly lower electron temperature is also observed in the south at these lower pressures. Given that the difference in solar EUV (and corresponding neutral heating) is ~20% between the two summer seasons, we postulate that the significantly lower plasma densities (above the demagnetization altitude) in the northern summer are due in part to an increase in ionospheric loss. This loss may be associated with the acceleration of ionospheric particles by the draped magnetic fields at an altitude where ions are not demagnetized. Furthermore, the loss may be diminished in the southern hemisphere where crustal magnetic fields increase the standoff distance to the solar wind magnetic field.

How to cite: Pilinski, M., Andersson, L., and Thiemann, E.: Hemispheric Asymmetry in the Mars Summer Ionosphere at Various Solar Forcing Conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12363, https://doi.org/10.5194/egusphere-egu2020-12363, 2020.

EGU2020-16452 | Displays | PS1.2

Mars’ ionopause: A game of pressures

Beatriz Sanchez-Cano, Clara Narvaez, Mark Lester, Michael Mendillo, Majd Mayyasi, and Mats Holmstrom

The ionopause is a tangential discontinuity in the ionospheric thermal plasma density profile that marks the upper boundary of the ionosphere for unmagnetized planets. This interface is formed by a balance of pressures, as the ionopause is the region where the total pressure of the ionosphere (ionospheric thermal pressure plus magnetic pressure) balances the solar wind ram pressure. Since only Venus and Mars have no global “dipole” magnetic fields, ionopauses are unique to those planets. For Venus, the ionopause formation is well characterized because the thermal pressure of the ionosphere is usually larger than the solar wind dynamic pressure. For Mars, however, the maximum thermal pressure of the ionosphere is usually insufficient to balance the total pressure in the overlying magnetic pileup boundary. Therefore, the Martian ionopause is not always formed, and when it does, it is located at a large range of altitudes, varies rapidly and is highly structured. In this study, we characterise the Martian ionopause formation from the point of view of the thermal, magnetic and dynamic pressure balance. The objective of this paper is to assess under which circumstances the Martian ionopause is formed, both over and far from crustal magnetic fields. We focus on three MAVEN deep dip campaigns that occurred on the dayside of Mars, and we utilize several multi-plasma and magnetic field in-situ observations from the MAVEN mission, as well as solar wind plasma observations from the Mars Express mission.

How to cite: Sanchez-Cano, B., Narvaez, C., Lester, M., Mendillo, M., Mayyasi, M., and Holmstrom, M.: Mars’ ionopause: A game of pressures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16452, https://doi.org/10.5194/egusphere-egu2020-16452, 2020.

EGU2020-6354 | Displays | PS1.2

ESCAPADE: coordinated multipoint measurements of Mars' near-space plasma environment

Robert Lillis, Shannon Curry, Christopher Russell, Janet Luhmann, Aroh Barjatya, Davin Larson, Ronan Modolo, Roberto Livi, Phyllis Whittlesey, Yuki Harada, Christopher Fowler, Shaosui Xu, David Brain, Paul Withers, and Edward Thiemann

Multi-spacecraft missions after 2000 (Cluster II, THEMIS, Van Allen Probes, and MMS) have revolutionized our understanding of the causes, patterns and variability of a wide array of plasma phenomena in the terrestrial magnetospheric environment. ESCAPADE is a twin-spacecraft Mars mission concept that will similarly revolutionize our understanding of how solar wind momentum and energy flows throughout Mars’ magnetosphere to drive ion and sputtering escape, two processes which have helped shape Mars’ climate evolution over solar system history. 

ESCAPADE will measure magnetic field strength and topology, ion plasma distributions (separated into light and heavy masses), as well as suprathermal electron flows and thermal electron and ion densities, from elliptical, 200 km x 7000 km orbits. ESCAPADE are small spacecraft (<90 kg), traveling to Mars via solar electric propulsion as a rideshare with the Psyche metal-asteroid mission in August 2022, matching Mars’ heliocentric orbit until capture and spiral-down to science orbits. ESCAPADE’s strategically-designed 1-year, 2-part scientific campaign of temporally and spatially-separated multipoint measurements in different parts of Mars’ diverse plasma environment, will allow the cause-and-effect of solar wind control of ion and sputtering escape to be unraveled for the first time. Figure 1 shows ESCAPADE’s orbits within a hybrid simulation of the solar wind interaction with Mars, where the color scale represents ion velocity, blue lines are magnetic field, while white lines are sample proton trajectories and spacecraft orbits.

ESCAPADE has been selected for Phase A and B study by NASA as one of three finalists in the SIMPLEX-II program.  We will report on science goals, engineering and mission design challenges, and provide a status update.

How to cite: Lillis, R., Curry, S., Russell, C., Luhmann, J., Barjatya, A., Larson, D., Modolo, R., Livi, R., Whittlesey, P., Harada, Y., Fowler, C., Xu, S., Brain, D., Withers, P., and Thiemann, E.: ESCAPADE: coordinated multipoint measurements of Mars' near-space plasma environment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6354, https://doi.org/10.5194/egusphere-egu2020-6354, 2020.

We study the solar wind interaction with Venus in a 3-dimensional global hybrid model where ions are treated as particles and electrons are a charge-neutralizing fluid. We concentrate on large-scale ultra-low frequency (ULF) waves in the ion foreshock and how they affect the energization and escape of planetary ions. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is smaller than about 45 degrees. The magnetic connection with the bow shock allows backstreaming of the solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter the bow shock and transmit in the downstream region. We analyze the coupling of the ULF waves with the planetary ion acceleration and compare Venus and Mars in a global hybrid simulation.

How to cite: Jarvinen, R., Kallio, E., and Pulkkinen, T.: Modulation of the solar wind driven ion escape from unmagnetized planets by ultra-low-frequency foreshock waves in a global hybrid simulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6891, https://doi.org/10.5194/egusphere-egu2020-6891, 2020.

EGU2020-7497 | Displays | PS1.2

Statistical occurrence of mirror mode waves at Mars

Cyril Simon Wedlund, Martin Volwerk, Christian Mazelle, Christian Möstl, Diana Rojas-Castillo, Jared Espley, and Jasper Halekas

Ultra low-frequency wave activity such as mirror mode (MM) waves, arising from an ion temperature anisotropy in the plasma, has been ubiquitously detected in the magnetosheaths of Venus and Mars. The MM instability is usually triggered behind a quasi-perpendicular bow shock in a high plasma β. We present here a statistical survey of these waves at Mars using magnetometer and ion data from the NASA/MAVEN mission between 2014 and 2019 (solar cycle 24, receding activity). First, quasi-perpendicular bow shock crossings are identified in the data using simple bow shock models (Edberg et al. 2008, Gruesbeck et al. 2018, Hall et al. 2019). MM waves are then automatically detected for these conditions, first from magnetometer measurements only (in the manner of Volwerk et al., 2016), and second using both magnetometer and ion moments to refine the analysis. Maps of MM wave occurrence for solar cycle 24 are presented and preliminary comparisons with similar and different solar activity conditions with MGS and Mars Express data are discussed.

How to cite: Simon Wedlund, C., Volwerk, M., Mazelle, C., Möstl, C., Rojas-Castillo, D., Espley, J., and Halekas, J.: Statistical occurrence of mirror mode waves at Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7497, https://doi.org/10.5194/egusphere-egu2020-7497, 2020.

EGU2020-7864 | Displays | PS1.2

Crustal magnetic fields at Mars and ion escape

Eduard Dubinin, Markus Fraenz, Marin Pätzold, Joachim Woch, Kai Fan, Yong Wei, Jim McFadden, Olga Tsareva, and Lev Zelenyi

Does an intrinsic field inhibits or enhances ion escape from planetary ionospheres is still an unsolved issue. Mars does not possess a global intrinsic magnetic field but instead has the strong crustal magnetic fields localized mainly in the southern hemisphere. The crustal magnetic field significantly influences the interaction of the solar wind with Mars adding features typical for planets with a global intrinsic magnetic field. Therefore it is interesting to compare ion losses from the ionosphere regions with and without strong crustal fields. Recently such studies were performed and have shown a protective effect of the crustal field on escape of the energized (E > 30 eV) oxygen ions (e.g. Fan et al., Geophysical Review Letters, 2019). However, the main bulk of escaping ions at Mars have energy lower than 30 eV. We will present the results of influence of the crustal magnetic field at Mars on the total losses of O+ and O2+ ions. The global picture of ion escape occurs more complex. Effects of larger ionospheric areas above the crustal field sources exposed by solar wind compensate a shielding effect at lower altitudes. As a result, the ion losses from the southern ionosphere of Mars might be even higher than losses from the northern “unmagnetized” ionosphere.

How to cite: Dubinin, E., Fraenz, M., Pätzold, M., Woch, J., Fan, K., Wei, Y., McFadden, J., Tsareva, O., and Zelenyi, L.: Crustal magnetic fields at Mars and ion escape, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7864, https://doi.org/10.5194/egusphere-egu2020-7864, 2020.

EGU2020-9757 | Displays | PS1.2

Effects of the solar wind dynamic pressure on the accelerated cometary ions in the magnetosphere of comet 67P

Aniko Timar, Zoltan Nemeth, Karoly Szego, Melinda Dósa, and Balazs Nagy

Rosetta observed medium-energy ions around comet 67P/Churyumov-Gerasimenko while orbiting deep inside the coma. These ions are thought to be accelerated towards the anti-sunward direction by some acceleration mechanism in the outer regions of the cometary magnetosphere. They usually reach energies up to 100-1000 eV and undergo deceleration in the dense neutral coma surrounding the nucleus. These ions usually appear in the ion dynamic spectrum as a new population rising from the low energy background, their energy peaking around 1000 eV and then decreasing until the population disappears again. We investigated the properties of these ions, as well as the relationship between the solar wind pressure and the energy of the medium-energy ions to discover the cause of the observed time variation. We show that there is a correlation between the solar wind dynamic pressure around the comet and the energy of the accelerated ions.

How to cite: Timar, A., Nemeth, Z., Szego, K., Dósa, M., and Nagy, B.: Effects of the solar wind dynamic pressure on the accelerated cometary ions in the magnetosphere of comet 67P, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9757, https://doi.org/10.5194/egusphere-egu2020-9757, 2020.

EGU2020-10492 | Displays | PS1.2

Localized heating of the Martian topside ionosphere through the combined effects of magnetic pumping by large scale magnetosonic waves and pitch angle diffusion by whistler waves

Christopher Fowler, Oleksiy Agapitov, Shaosui Xu, David Mitchell, Laila Andersson, Anton Artemyev, Jared Espley, Robert Ergun, and Christian Mazelle

We present Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of periodic (~ 25 s) large scale (100s km) magnetosonic waves propagating into the Martian dayside upper ionosphere. These waves adiabatically modulate the superthermal electron distribution function, and the induced electron temperature anisotropies drive the generation of observed electromagnetic whistler waves. The localized (in altitude) minimum in the ratio fpe / fce provides conditions favorable for the local enhancement of efficient wave-particle interactions, so that the induced whistlers act back on the superthermal electron population to isotropize the plasma through pitch angle scattering. These wave-particle interactions break the adiabaticity of the large scale magnetosonic wave compressions, leading to local heating of the superthermal electrons during compressive wave `troughs'. Further evidence of this heating is observed as the subsequent phase shift between the observed perpendicular-to-parallel superthermal electron temperatures and compressive wave fronts. Such a heating mechanism may be important at other unmagnetized bodies such as Venus and comets.

How to cite: Fowler, C., Agapitov, O., Xu, S., Mitchell, D., Andersson, L., Artemyev, A., Espley, J., Ergun, R., and Mazelle, C.: Localized heating of the Martian topside ionosphere through the combined effects of magnetic pumping by large scale magnetosonic waves and pitch angle diffusion by whistler waves, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10492, https://doi.org/10.5194/egusphere-egu2020-10492, 2020.

We report the preliminary results of a hybrid simulation to differentiate and quantify the energy gain due to different electric field terms in the acceleration of planetary ions escaping from an induced magnetosphere. 

The planetary ions gain energy from the electric field formed in the induced magnetosphere. The electric field is not directly measurable and thus has to be expressed by the generalized Ohm's law with measurable quantities:

E = -Ve×B - ∇Pe/(qene) + j×B/(qene)

Where Ve is the velocity of the electrons that freeze the magnetic field B, Pe is the thermal pressure tensor, and j is the Hall current. The three terms on the right-hand side describe the three different mechanisms of ion acceleration: the motional term, the pressure gradient term, and the Hall term. All these terms contribute to the energization of escaping ions, while they dominate in different positions in an induced magnetosphere, and play different roles in the dynamics of an escaping ion.

We will quantify the energy gain due to each electric field term of escaping ions depending on the birthplaces of the ions. Our tool is AMITIS, a GPU-based 3-D hybrid code (ions as particles and electrons as a fluid) to model the plasma interaction with a planet (Fatemi et al., 2017). For a test, we simulated the solar wind interaction with Mars at nominal space environment conditions until a quasi-steady state. We calculated different electric field terms and compared them with the MAVEN measurements. The simulation results show good agreement with measurements in both magnitude and spatial distribution.

 

We further launched test particles from different positions in the ionosphere and tracked the energy gain/loss due to different electric field terms along their escaping trajectories. The energization history of an ion depends on its trajectory, which further partly depends on the birthplace of the ion. Ions produced outside of the IMB are accelerated or “picked up” totally by the motional electric field. Ions produced in the induced magnetosphere in the dayside may be accelerated by the thermal pressure gradient of the ionosphere, while those produced in the nightside are driven more by the Hall electric field.

How to cite: Wang, X.-D. and Fatemi, S.: Acceleration of Planetary Ions by Different Electric Field Terms in an Induced Magnetosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11419, https://doi.org/10.5194/egusphere-egu2020-11419, 2020.

EGU2020-13746 | Displays | PS1.2

The dependence of deep-nightside Martian ionosphere TEC on crustal magnetic field

Junfeng Qin, Hong Zou, Yuguang Ye, Jinsong Wang, and Erling Nielsen

It has been clear that the main cause of Martian deep-nightside ionosphere is electron precipitation, which is dominated by Martian crustal magnetic field. In this research, the dependence of deep-nightside Martian ionosphere TEC (Total Electron Content) on crustal magnetic field was studied based on Martian ionospheric TEC data from MEX/MARSIS and 400km crustal magnetic field data from MGS. It is found that the strength and inclination of crustal magnetic field have great effects on Martian deep-nightside ionospheric TEC. This kind of effects are worth to be compared with the effects of crustal magnetic field on electron precipitation studied in previous researches (such as Lillis and Brain, 2013, Nightside electron precipitation at Mars: Geographic variability and dependence on solar wind conditions) to find out more about the formation of Martian deep-nightside ionosphere. It is also found that, in a Martian crustal magnetic field cusp region, the observed deep-nightside ionospheric TECs in the center of the cusp are lower than those in the edge of the cusp, a phenomenon not noticed before. It indicates that there may be more precipitated electrons moving along the closed crustal magnetic lines than moving along open crustal magnetic lines, and these precipitated electrons in closed magnetic lines can be related to the energy processes in the nightside of Mars, such as magnetic reconnections.

How to cite: Qin, J., Zou, H., Ye, Y., Wang, J., and Nielsen, E.: The dependence of deep-nightside Martian ionosphere TEC on crustal magnetic field, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13746, https://doi.org/10.5194/egusphere-egu2020-13746, 2020.

EGU2020-13754 | Displays | PS1.2

Degenerate induced magnetospheres

Stas Barabash, Andrii Voshchepynets, Mats Holmström, Futaana Yoshifumi, and Robin Ramstad

Induced magnetospheres of non-magnetized atmospheric bodies like Mars and Venus are formed by magnetic fields of ionospheric currents induced by the convective electric field E = - V x B/c of the solar wind. The induced magnetic fields create a magnetic barrier which forms a void of the solar wind plasma, an induced magnetosphere. But what happens when the interplanetary magnetic field is mostly radial and the convective field E ≈ 0? Do a magnetic barrier and solar wind void form? If yes, how such a degenerate induced magnetosphere work? The question is directly related to the problem of the atmospheric escape due to the interaction with the solar and stellar winds. The radial interplanetary magnetic field in the inner solar system is typical for the ancient Sun conditions and exoplanets on near-star orbits. Also, the radial interplanetary field may provide stronger coupling of the near-planet environment with the solar/stellar winds and thus effectively channels the solar/stellar wind energy to the ionospheric ions. We review the current works on the subject, show examples of degenerate induced magnetospheres of Mars and Venus from Mars Express, Venus Express, and MAVEN measurements and hybrid simulations, discuss physics of degenerate induced magnetospheres, and impact of such configurations on the escape processes.

How to cite: Barabash, S., Voshchepynets, A., Holmström, M., Yoshifumi, F., and Ramstad, R.: Degenerate induced magnetospheres, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13754, https://doi.org/10.5194/egusphere-egu2020-13754, 2020.

EGU2020-16717 | Displays | PS1.2

A Statistical Analysis of Radar Blackout Events at Mars

Mark Lester, Beatriz Sanchez-Cano, Hannah Biddle, Daniel Potts, Pierre-Louis Blelly, Hermann Opgenoorth, Olivier Witasse, Marco Cartacci, Roberto Orosei, Fabrizio Bernardini, Nathaniel Putzig, Bruce Campbell, Robert Lillis, François Leblanc, Steve Milan, and John M.C. Plane

The loss of signal detection by the sub surface radars currently operational on Mars Express and Mars Reconnaissance Orbiter can be evidence of enhanced ionisation at lower altitudes in the Martian atmosphere as a result of solar energetic particles penetrating to these altitudes.  The MARSIS instrument on Mars Express and SHARAD on MRO operate at different frequencies, with MARSIS up to 5 MHz and SHARAD between 10 and 20 MHZ.  In addition MARSIS can operate in an additional mode as an Active Ionospheric Sounder, although here we focus only on the sub surface mode.  We present an analysis of the data during the lifetimes of both instruments, extending from 2005 to 2018.  Here we identify the radar blackouts as either total or partial and investigate their occurrence as a function of solar cycle.  We find a clear solar cycle dependence with more events occurring during the solar maximum years, as expected.  However, we also note the duration of events is often much longer than expected, in excess of several days, sometimes reaching 10 – 14 days.  Investigation of other data sets, notably from the MAVEN SEP instrument complements the analysis.  We finally compare our observations at Mars with similar observations at Earth.

How to cite: Lester, M., Sanchez-Cano, B., Biddle, H., Potts, D., Blelly, P.-L., Opgenoorth, H., Witasse, O., Cartacci, M., Orosei, R., Bernardini, F., Putzig, N., Campbell, B., Lillis, R., Leblanc, F., Milan, S., and Plane, J. M. C.: A Statistical Analysis of Radar Blackout Events at Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16717, https://doi.org/10.5194/egusphere-egu2020-16717, 2020.

EGU2020-17083 | Displays | PS1.2

Dusty plasma effects in the nighttime ionosphere of mars

Yulia Izvekova, Sergey Popel, and Alina Besedina

A self-consistent consideration of the motion of dust particles in plasma systems in the atmosphere of Mars can lead to the detection of oscillations and waves, which, in particular, can be detected from the surface of the planet. The presence of local magnetic fields leads to significant inhomogeneities in the ionosphere of Mars, especially noticeable on the night side. On the night side of the ionosphere, there are areas of sharp increase in electron concentrations in areas where the lines of force of the magnetic field are perpendicular to the surface of the planet. In the areas where the magnetic field is parallel to the surface, the electrons of the solar wind do not penetrate the atmosphere and there is no ionization. Horizontal gradients of electron density on the night side can exceed 10 ^ 4 cm ^ -3 for several tens of kilometers. Such high plasma density gradients lead to local plasma transfer perpendicular to the external magnetic field, horizontal currents and electric fields are generated. Interaction of the plasma of the solar wind with a plasma containing dust particles can lead to the generation of high-frequency waves.

The work is supported by the Russian Science Foundation (project No 18-72-00119).

How to cite: Izvekova, Y., Popel, S., and Besedina, A.: Dusty plasma effects in the nighttime ionosphere of mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17083, https://doi.org/10.5194/egusphere-egu2020-17083, 2020.

EGU2020-18500 | Displays | PS1.2

Sounder Accelerated Particles at Mars: Observations, Mechanisms, and Applications

Andrii Voshchepynets, Stas Barabash, Mats Holmstrom, Rudy Frahm, and Andrew Kopf

We report the first observations of sounder accelerated particles (SAP) in the ionosphere of a planet which does not possess a strong magnetic field (Mars). These observations were conducted onboard the Mars Express spacecraft by the ion and electron sensors of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment and the powerful topside sounder: Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS). Accelerated ions (O2+ , O+, and lighter ions) are observed in an energy range up to 800 eV when MARSIS transmits at a frequency close to the plasma frequency. Individual observations consist of almost monoenergetic ion beams either aligned with the MARSIS antenna or lying in the perpendicular plane. The observed ion beams are often accompanied by a decrease in the electron flux. Accelerated electrons are observed at energies up to 400 eV when MARSIS transmits at a frequency between the local plasma frequency and its harmonics (up to four times the plasma frequency). The majority of the sounder accelerated electrons are recorded close to the regions of intense crustal magnetic fields. The voltage applied to the MARSIS antenna causes spacecraft charging to 100’s of volts by electrons from the ambient plasma. Positively charged ions are accelerated when the spacecraft discharges. Accelerated photoelectrons are released by the highly charged spacecraft and after one gyration in the strong magnetic field, return to the spacecraft which has already discharged. The acceleration effect influences which ions can be observed by increasing the energy of the thermal ion species making it possible to detect them whereas they would be indistinguishable under normal circumstances. We present the relevant data and discuss how these effects can be used for diagnostic of the local plasma.

How to cite: Voshchepynets, A., Barabash, S., Holmstrom, M., Frahm, R., and Kopf, A.: Sounder Accelerated Particles at Mars: Observations, Mechanisms, and Applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18500, https://doi.org/10.5194/egusphere-egu2020-18500, 2020.

EGU2020-19305 | Displays | PS1.2

A study of kinematic relaxation at the Venus bow shock

Simon A. Pope and Michael A. Balikhin

A new type of very-low Mach number shock in which the primary method of energy re-distribution is the kinematic relaxation of a non-gyrotropic ion population, was discovered at Venus early in the Venus Express mission. This led to the development of an associated theory and numerical analysis. The recent discovery of such a shock at the Earth using THEMIS data experimentally verified this theory using simultaneous magnetic field and plasma data. It also showed that the most favourable conditions for the formation of such a shock is the magnetic cloud phase of an ICME. Venus Express provides an excellent opportunity to study such shocks further. Here we present results from the duration of the mission, which identifies over thirty shock crossings showing evidence of kinematic relaxation. These shock crossings are investigated to understand how the upstream conditions and heavy ions (including pick-up ions) affect their formation.

How to cite: Pope, S. A. and Balikhin, M. A.: A study of kinematic relaxation at the Venus bow shock, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19305, https://doi.org/10.5194/egusphere-egu2020-19305, 2020.

EGU2020-20178 | Displays | PS1.2

Rosetta electric field observations in the plasma environment of comet 67P/Churyumov-Gerasimenko

Elias Odelstad, Tomas Karlsson, and Anders Eriksson
The plasma environments of active comets are dominated by the interaction of the solar wind with newly born cometary heavy ions, predominantly water group ions produced by ionization of cometary neutral volatiles over large distances in the extensive and diffuse cometary coma. The resulting vast comet-solar wind interaction region hosts a plethora of plasma instabilities, waves and turbulence phenomena, and thus constitutes a formidable natural laboratory for studying such processes.
 
Waves are also important in determining many of the plasma properties of this environment. They can, e.g., heat or cool plasma populations, create supra-thermal electrons responsible for X-ray emissions, reduce plasma anisotropies and gradients, couple different plasma species, and provide anomalous resistivity.
 
Electric field measurements in the cometary plasma environment have until recently been rare, and have only been performed during short fly-by missions, at relatively large distances from the comet nucleus. The electric field measurements by the LAP instrument onboard the Rosetta spacecraft, collected during more than two years in the vicinity of comet 67P/Churyumov-Gerasimenko therefore represent a truly unique data set.
 
We use the database of 60 Hz electric field measurements of waves in the lower-hybrid frequency range, and correlate the comet-related parameters, (relative spacecraft position, solar distance, plasma and neutral gas density, etc.) with wave related parameters, such as amplitude/spectral density and frequency. We also compare statistically the properties of the waves with theoretical predictions of lower-hybrid wave generation, regarding e.g. amplitude dependence on plasma density gradients, with the aim of clarifying the importance of the plasma waves in different regions of the cometary plasma environment.
 
Electric field measurements allow investigating both electrostatic wave modes and electromagnetic ones. We investigate frequencies and amplitudes of the electric field oscillations and use background magnetic field values and plasma properties to determine relevant expected frequencies, as well as magnetic field oscillations (for low and medium frequencies) to determine if the plasma waves are electrostatic or electromagnetic. Lower hybrid waves are almost electrostatic, but have a small magnetic field signature from second order effects. Determination of the most common wave modes gives an indication of the role of plasma waves in the cometary plasma environment probed by Rosetta.
 
Lower hybrid waves are common in the inner coma of 67P. Such waves are predicted to energize electrons parallel to the ambient magnetic field, and ions in the perpendicular direction. With the help of ion and electron data, we test this prediction, which may explain the presence of a hot electron population reported on, but of hitherto unknown origin. These results give clues to the role of the waves in the formation of the cometary plasma environment.

How to cite: Odelstad, E., Karlsson, T., and Eriksson, A.: Rosetta electric field observations in the plasma environment of comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20178, https://doi.org/10.5194/egusphere-egu2020-20178, 2020.

EGU2020-20751 | Displays | PS1.2

MHD Predictions of Plasma Conditions Above Insight Landing Site based on MAVEN observations

Yingjuan Ma, Chris Russell, Yanan Yu, Andrew Nagy, Gabor Toth, and Bruce Jakosky2

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission was launched on 5 May 2018 and successfully landed at Elysium Planitia (4.5oN, 135.9oE)on Mars on 26 November 2018. The InSight Lander carries a magnetometer to measure disturbances from the Martian ionosphere. In order to understand the daily variations in the magnet field measurements on Martian surface, in this study, we use the time-dependent MHD model to study how plasma conditions vary with local time above insight landing site using solar wind condition from MAVEN observation. Significant diurnal variations can be seen in all plasma quantities due to solar wind interactions and planetary rotation. The induced magnetic field is mainly in the same direction as the upstream IMF. However, it seems that the variations seen by the Insight magnetometer cannot be only due to the interaction of the solar wind. We also add a neutral wind effect in our simulations to further investigate possible causes of surface field changes.

How to cite: Ma, Y., Russell, C., Yu, Y., Nagy, A., Toth, G., and Jakosky2, B.: MHD Predictions of Plasma Conditions Above Insight Landing Site based on MAVEN observations , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20751, https://doi.org/10.5194/egusphere-egu2020-20751, 2020.

EGU2020-20922 | Displays | PS1.2

Modeling Ionospheric Densities and Flows in Crustal and Draped Magnetic Fields at Mars

Antonio Renzaglia, Thomas Cravens, Christopher Fowler, Ali Rahmati, Shotaro Sakai, Jack Connerney, Mehdi Benna, and Laila Andersson

NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) explorer has been in orbit around Mars for over 5 years now, collecting valuable data about the planet. Specifically, the Langmuir Probe and Waves (LPW), the Neutral Gas and Ion Mass Spectrometer (NGIMS), and the Suprathermal and Thermal Ion Composition (STATIC) instruments measure important ionospheric properties. The instruments measure electron densities and temperature (LPW), neutral gas and ion composition (NGIMS), and the properties of escaping ions (STATIC). Electron and ion density and flux measurements are presented. The data indicates significant differences in ion properties between open crustal, closed crustal, and draped magnetic fields. Similar differences are noted for electrons as well. An ionospheric model has been developed that produces a profile of the ionosphere. The model then explores the evolution of the ionosphere, via chemistry and transport. At low altitudes (z<300 km), chemistry dominates, while transport dominates at higher altitudes. Results show significant differences in the ionosphere between the types of fields. The model utilizes data from the Magnetometer (MAG) instrument to provide properties of magnetic fields at Mars. The model may also help explain some of the atmospheric loss occurring at Mars. This is compared to data from STATIC. Analytic arguments for subsonic vs supersonic flow speeds (in the open field case) are also presented.

How to cite: Renzaglia, A., Cravens, T., Fowler, C., Rahmati, A., Sakai, S., Connerney, J., Benna, M., and Andersson, L.: Modeling Ionospheric Densities and Flows in Crustal and Draped Magnetic Fields at Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20922, https://doi.org/10.5194/egusphere-egu2020-20922, 2020.

PS1.3 – Planetary, Solar and Heliospheric Radio Emissions

EGU2020-1025 | Displays | PS1.3

On the fine structures in interplanetary radio emissions

Immanuel Christopher Jebaraj, Jasmina Magdalenic, and Stefaan Poedts

Solar radio emission is studied for many decades and a large number of studies have been dedicated to metric radio emission originating from the low corona. It is generally accepted that solar radio emission  observed at wavelengths below the metric range is produced by the coherent plasma emission mechanism. Fine structures seem to be an intrinsic part of solar radio emission and they are very important for understanding plasma processes in the solar medium. Extensive reporting and number of studies of the metric range fine structures were performed, but studies of fine structures in the interplanetary domain are quite rare. New and advanced ground-based radio imaging spectroscopic techniques (e.g. LOFAR, MWA, etc.,) and space-based observations (Wind/WAVES, STEREO/WAVES A & B, PSP, and SolO in the future) provide a unique opportunity to study radio fine structures observed  all the way from metric to kilometric range.

Radio signatures of solar eruptive events, such as flares and CMEs, observed in the interplanetary space are mostly confined to type II (radio signatures of magneto-hydrodynamic shock waves), and type III  bursts(electron beams propagating along open and quasi-open magnetic field lines). In this study, we have identified, and analyzed three types of fine structures present within the interplanetary radio bursts. Namely, the striae-like fine structures within type III bursts, continuum-like emission patches, and very slow drifting narrowband structures within type II radio bursts. Since space-based radio observations are limited to dynamic spectra, we use the novel radio triangulation technique employing direction finding measurements from stereoscopic spacecraft (Wind/WAVES, STEREO/WAVES A & B) to obtain the 3D position of the radio emission. The novelty of the technique is that it is not dependent on a density model and in turn can probe the plasma density in the triangulated radio source positions (Magdalenic et al. 2014). Results of the study show that locating the radio source helps not only to understand the generation mechanism of the fine structures but also the ambient plasma conditions such as e.g. electron density. We found that fine structures are associated with complex CME/shock wave structures which interact with the ambient magnetic field structures. We also discuss the possible relationship between the fine structures, the broadband emission they are part of, and the solar eruptive events they are associated with.

How to cite: Jebaraj, I. C., Magdalenic, J., and Poedts, S.: On the fine structures in interplanetary radio emissions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1025, https://doi.org/10.5194/egusphere-egu2020-1025, 2020.

EGU2020-1252 | Displays | PS1.3

Spectral Analysis of Solar Radio Type III Bursts from 10 kHz to 80 MHz

Kantepalli Sasikumar Raja, Milan Maksimovic, Xavier Bonnin, Philippe Zarka, Laurent Lamy, Eduard P. Kontar, Alain Lecacheux, Vratislav Krupar, Baptiste Cecconi, Nora Lahmiti, and Laurent Denis

Solar radio type III bursts are produced by electron beams that are propagating along the open magnetic field lines in the corona and interplanetary medium (IPM). They are the intense, fast drifting, and frequently observed bursts. Recently, it was reported that observations of type III bursts show a maximum spectral response at around 1 MHz. But this behavior of type III bursts is not sufficiently discussed in the literature. In order to understand this behavior we have revisited this problem and studied 2279 isolated type III bursts that are observed with Wind/Waves instrument (from space during 1995-2009) in the frequency range 10 kHz-14 MHz and found that all of them show a maximum spectral response at around 1 MHz. Since type III bursts are somewhat directive, we have studied separately, another 115 type III bursts that are simultaneously observed (in 2013-2014) using Wind/Waves and ground-based facility Nancay Decameter Array (10-80 MHz) and compared the spectral profiles. In this presentation, we will discuss the observations, applied calibration techniques and the possible theoretical explanation of why type III bursts show such behavior. 

How to cite: Sasikumar Raja, K., Maksimovic, M., Bonnin, X., Zarka, P., Lamy, L., Kontar, E. P., Lecacheux, A., Krupar, V., Cecconi, B., Lahmiti, N., and Denis, L.: Spectral Analysis of Solar Radio Type III Bursts from 10 kHz to 80 MHz, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1252, https://doi.org/10.5194/egusphere-egu2020-1252, 2020.

EGU2020-14784 | Displays | PS1.3

Strongly structured radio emission observed by LOFAR on August 25, 2014

Jasmina Magdalenic, Christophe Marque, Richard Fallows, Gottfried Mann, Christian Vocks, and Pietro Zucca

On August 25, 2014, NOAA AR 2146 produced the M2.0 class flare (peaked at 15:11 UT). The flare was associated with a halo CME and a radio event observed by LOFAR (the LOw-Frequency Array). The radio event consisted of a type II, type III and type IV radio emissions. In this study, we present LOFAR observations of the type II (radio signatures of shock waves) and type III bursts (radio signatures of fast electron beams propagating along open or quasi open field lines).  Both, the type II burst and type III bursts show strong fragmentation of the radio emission. Although fine structures of type II bursts were already reported, the richness of the fine structures observed in the studied event is unprecedented. We found type II fine structures morphologically very similar to the ones sometimes seen superposed on type IV continuum emission, and similar to simple narrowband super short structures (Magdalenic et al., 2006). The group of type III bursts was as usually, observed during the impulsive phase of the flare. The high frequency/time resolution LOFAR observations reveal that only few of the observed type III bursts have a smooth emission profile, and the majority of bursts is strongly fragmented. Surprisingly, fine structures of some type III bursts show similarities to the fine structures observed in the type II burst, but on a smaller frequency scale. Some of the type III bursts show a non-organized patchy structure which gives an indication on the possibly related turbulence processes. We show that these LOFAR observations bring completely new insight and pose a new challenge for the physics of the acceleration of electron beams and associated emission processes.

How to cite: Magdalenic, J., Marque, C., Fallows, R., Mann, G., Vocks, C., and Zucca, P.: Strongly structured radio emission observed by LOFAR on August 25, 2014, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14784, https://doi.org/10.5194/egusphere-egu2020-14784, 2020.

EGU2020-21394 | Displays | PS1.3

Analysis of solar radio imaging-spectroscopic observations

Yihua Yan, Minghui Zhang, Zhichao Zhou, Xingyao Chen, Chengming Tan, Baolin Tan, Wei Wang, Linjie Chen, Fei Liu, Lihong Geng, Zhijun Chen, Yin Zhang, and Muser Team

Solar radio fine structures observed in wide frequency ranges are manifestations of the physical processes related to the energy release, particle accelerations and propagations, etc. The locations of these fine structures are mostly not clear so it is important to have imaging spectroscopic observations to address these problems.

Mingantu Spectral Radioheliograph (MUSER) is an aperture-synthesis imaging telescope, dedicated to observe the Sun, operating on multiple frequencies in dm to cm range. The ability of MUSER allows one to diagnose coronal magnetic field and the plasma parameters such as electron beam velocity, density, spectral index, etc.

During 2014 to 2019, MUSER has registered a number of solar radio bursts corresponding to 2 X-class, 15 M-class, 38 C-class, 19 B-class, 4 A-class and 5 below A-class flares as well as quiet Sun observations. Here we demonstrate some interesting events from MUSER imaging-spectroscopic observations.

How to cite: Yan, Y., Zhang, M., Zhou, Z., Chen, X., Tan, C., Tan, B., Wang, W., Chen, L., Liu, F., Geng, L., Chen, Z., Zhang, Y., and Team, M.: Analysis of solar radio imaging-spectroscopic observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21394, https://doi.org/10.5194/egusphere-egu2020-21394, 2020.

EGU2020-7876 | Displays | PS1.3

Solar Type III radio bursts at Saturn’s orbit: Case study of stereoscopic observations by Cassini/RPWS and Wind/WAVES experiments

Ahmed Abou el-Fadl, Mohammed Boudjada, Patrick H.M. Galopeau, Muhamed Hammoud, and Helmut Lammer

Type III radio bursts are produced by electron beams accelerated in active regions and following open magnetic field lines. Type III observed frequency is found to be nearly equal to the plasma frequency directly linked to the local electron density. The source regions of such solar bursts are the solar corona and the interplanetary medium where, respectively, higher and lower frequencies are generated. In this work, we consider specific Type III solar bursts simultaneously observed by Cassini/RPWS and Wind/WAVES experiments. Despite the distance of Cassini spacecraft to the Sun such Type III bursts have been detected at Saturn’s orbit, i.e. at about 10AU. Those considered bursts are covering a frequency bandwidth from about 10 MHz down to 100 kHz. We attempt in this study to characterize the spectral pattern, i.e. the flux density versus the observation time and the frequency range, and the visibility of the source regions to the observer (i.e. Wind and Cassini spacecraft). In this context, we analyze the evolution of the Type III bursts from the solar corona and up to Saturn’s orbit taking into consideration the Archimedean spiral which is the geometrical configuration of the solar magnetic field extension in the interplanetary medium. We principally discuss the physical parameters, i.e. solar wind speed and the electron density, which lead to constraint the location of the source region and its visibility to both spacecraft.

How to cite: Abou el-Fadl, A., Boudjada, M., Galopeau, P. H. M., Hammoud, M., and Lammer, H.: Solar Type III radio bursts at Saturn’s orbit: Case study of stereoscopic observations by Cassini/RPWS and Wind/WAVES experiments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7876, https://doi.org/10.5194/egusphere-egu2020-7876, 2020.

We use five different Jupiter’s magnetic field models (O6, VIP4, VIT4, VIPAL and JRM09) to investigate the angular distribution of the Jovian decameter radiation occurrence probability, relatively to the local magnetic field B and its gradient B in the source region. The most recent model JRM09, proposed by Connerney et al. [Geophys. Res. Lett., 45, 2590-2596, 2018], was derived from Juno’s first nine orbits observations. The JRM09 model confirms the results obtained several years ago using older models (O6, VIP4, VIT4 and VIPAL): the radio emission is beamed in a hollow cone presenting a flattening in a specific direction. The same assumptions were made as in the previous studies: the Jovian decameter radiation is supposed to be produced by the cyclotron maser instability (CMI) in a plasma where B and B are not parallel. As a consequence, the emission cone does not have any axial symmetry and then presents a flattening in a privileged direction. This flattening appears to be more important for the northern emission (34.8%) than for the southern emission (12.5%) probably due to the fact that the angle between the directions of B and B is greater in the North (~10°) than in the South (~4°).

How to cite: Galopeau, P. and Boudjada, M.: Relevance of the magnetic field model for studying the beaming cone of the Jovian decameter emission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10781, https://doi.org/10.5194/egusphere-egu2020-10781, 2020.

EGU2020-19055 | Displays | PS1.3

New remote radio observations of Jupiter by Parker Solar Probe

Alain Lecacheux, Stuart D. Bale, Milan Maksimovic, and Marc Pulupa

The FIELDS/RFS experiment aboard the Parker Solar Probe spacecraft, in orbit around the Sun, is able to detect and remotely study low frequency radio emissions from Jupiter. Accurate measurements of the intensity and polarisation of those emissions (mainly the HOM/DAM components) were obtained throughout years 2018 and 2019. They are compared to similar ones, obtained 20 years ago, during Cassini’s remote flyby of Jupiter. A particular emphasis is brought on the so-called “attenuation bands” phenomenon, - a well-defined intensity extinction/enhancement feature modulating the HOM dynamic spectrum -, which likely results from the radiation propagating to the observer through some permanent or long lived plasma structure (not firmly identified so far) lying in the rotating Jovian inner magnetosphere.

How to cite: Lecacheux, A., Bale, S. D., Maksimovic, M., and Pulupa, M.: New remote radio observations of Jupiter by Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19055, https://doi.org/10.5194/egusphere-egu2020-19055, 2020.

EGU2020-2906 | Displays | PS1.3

Saturn lightning activity from a cyclone at 50°North latitude

Georg Fischer and Jacob Gunnarson

During the Cassini mission (2004-2017) the Radio and Plasma Wave Science (RPWS) experiment has recorded the lightning radio emissions from multiple thunderstorms in Saturn's atmosphere. Most of the storms were located in the storm alley at a planetocentric latitude of 35°South, and there was one extra-large storm at 35°North called "Great White Spot" (GWS), which emitted millions of SEDs. This is short for "Saturn Electrostatic Discharges", a widely-used synonym for the radio emission from Saturn lightning. Most lightning storms have also been observed by the Cassini cameras or by ground-based amateur astronomers as bright white spots with diameters around 2000 km ("smaller" storms in the storm alley) or as large as 10,000 km (GWS at 35°North).

In this presentation we focus on a cyclone at 50°North planetocentric latitude, which was observed by the Cassini cameras from 2007 until the end of 2013. Its average diameter was around 3000 km, and it also exhibited some weak SED activity. The first SED outbreak was in December 2010, at the same time when the GWS was raging further south. Due to the differences in longitude and SED rate of the 50°N cyclone compared to the GWS, it is partly possible to separate the SEDs emitted from the cyclone to those emitted from the GWS. The SED rate of the cyclone is rather low, typically a few SEDs per minute, whereas the GWS showed SED rates up to 10 SEDs per second. The SED activity of the 50°North cyclone was very intermittent, it usually lasted for a few weeks before disappearing again for several months. After the first outbreak in December 2010, there was some more activity in early 2011, autumn 2011, December 2011, spring 2012, July 2012, summer 2013, and finally autumn 2013. By comparing SED data from RPWS with images from the Cassini camera we will show that almost all SEDs taking place after the GWS had their origin in the 50°N cyclone, since the SED sub-spacecraft longitude range is consistent with the longitude of the cyclone. The last SED activity from this cyclone took place in November 2013, and it was also the last SED activity recorded by RPWS during the whole Cassini mission. No more SEDs were found from November 2013 until Cassini burned up in Saturn's upper atmosphere in September 2017.

 

How to cite: Fischer, G. and Gunnarson, J.: Saturn lightning activity from a cyclone at 50°North latitude, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2906, https://doi.org/10.5194/egusphere-egu2020-2906, 2020.

Dust storms on Mars are predicted to be capable of producing electrostatic fields and discharges, even larger than those in dust storms on Earth.  There are three key elements in the characterization of Martian electrostatic discharges: dependence on Martian environmental conditions, event rate, and the strength of the generated electric fields.  The detection and characterization of electric activity in Martian dust storms has important implications for habitability, and preparations for human exploration of the red planet. Furthermore, electrostatic discharges may be linked to local chemistry and plays an important role in the predicted global electrical circuit.

 

Because of the continuous Mars telecommunication needs of NASA’s Mars-based assets, the Deep Space Network (DSN) is the only facility in the world that combines long term, high cadence, observing opportunities with large sensitive telescopes, making it a unique asset worldwide in searching for and characterizing electrostatic activity from large scale convective dust storms at Mars. We will describe a program at NASA’s Madrid Deep Space Communication Complex that has been carrying out a long-term monitoring campaign to search for and characterize the entire Mars hemisphere for powerful discharges during routine tracking of spacecraft at Mars on an entirely non-interfering basis. The ground-based detections will also have important implications for the design of a future instrument that could make similar in-situ measurements from orbit or from the surface of Mars, with far greater sensitivity and duty cycle, opening up a new window in our understanding of the Martian environment.

How to cite: Majid, W.: Radio Emissions from Electrical Activity in Martian Dust Storms, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19929, https://doi.org/10.5194/egusphere-egu2020-19929, 2020.

PS1.4 – Planetary Space Weather

EGU2020-7422 | Displays | PS1.4 | Arne Richter Award for Outstanding ECS Lecture

Space Weather effects on Mars’ ionosphere: From our current knowledge to the way forward

Beatriz Sánchez-Cano

Planetary Space Weather is an emerging topic of increasing interest. Forecast this planetary space weather, however, is currently very challenging mainly due to the lack of continuous solar wind observations for each planet. In the particular case of Mars, understanding the ionospheric behaviour following Space Weather activity is essential in order to assess the response of the Martian plasma environment to the dissipation of energy from solar storms. Moreover, it gives information on the effects on the current technology deployed on the red planet. Despite the recent considerable exploration, however, there is still no continuous upstream solar wind observations at Mars. This fact makes the analysis of the different Martian plasma datasets challenging, relying on solar wind models and upstream solar wind observations at 1 AU (e.g. at Earth’s L1 point, STEREO, etc.) when Mars and those satellites are in apparent opposition or perfectly aligned in the Parker spiral.

This lecture will focus on our current knowledge of the Martian ionosphere, which is the layer that links the neutral atmosphere with space, and acts as the main obstacle to the solar wind. In particular, I will focus on our recent advances in the understanding of the Martian ionospheric reaction to different Space Weather events during the solar cycle, both from the data analysis and ionospheric modelling perspectives. Some important aspects to consider are the bow shock, magnetic pileup boundary, and ionopause characterization, as well as the behaviour of the topside and bottomside of the ionosphere taking into account the planet’s orbital eccentricity. Moreover, I will show the effect of electron precipitation from large Space Weather events in the very low Martian ionosphere, a region that it is non-accessible to in-situ spacecraft observations. Finally, I will conclude the presentation by giving my perspective on some of the key outstanding questions that remain unknown, and I consider they constitute the next generation of Mars’ ionospheric and Space Weather science and exploration.

How to cite: Sánchez-Cano, B.: Space Weather effects on Mars’ ionosphere: From our current knowledge to the way forward, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7422, https://doi.org/10.5194/egusphere-egu2020-7422, 2020.

EGU2020-13186 | Displays | PS1.4

Global Ten-Moment Multifluid Simulations of the Solar Wind Interaction with Mercury: From the Planetary Conducting Core to the Dynamic Magnetosphere

Chuanfei Dong, Liang Wang, Ammar Hakim, Amitava Bhattacharjee, James Slavin, Gina DiBraccio, and Kai Germaschewski

For the first time, we explore the tightly coupled interior‐magnetosphere system of Mercury by employing a three‐dimensional ten‐moment multifluid model. This novel fluid model incorporates the nonideal effects including the Hall effect, electron inertia, and tensorial pressures that are critical for collisionless magnetic reconnection; therefore, it is particularly well suited for investigating collisionless magnetic reconnection in Mercury's magnetotail and at the planet's magnetopause. The model is able to reproduce the observed magnetic field vectors, field‐aligned currents, and cross‐tail current sheet asymmetry (beyond magnetohydrodynamic approach), and the simulation results are in good agreement with spacecraft observations. We also study the magnetospheric response of Mercury to an extreme event with an enhanced solar wind dynamic pressure, which demonstrates the significance of induction effects resulting from the electromagnetically coupled interior. More interestingly, plasmoids (or flux ropes) are formed in Mercury's magnetotail during the event, indicating the highly dynamic nature of Mercury's magnetosphere. This novel ten‐moment multifluid model represents a crucial step toward establishing a revolutionary approach that enables the investigation of Mercury's tightly coupled interior‐magnetosphere system beyond the traditional fluid model and has the potential to enhance the science returns of both the MESSENGER mission and the BepiColombo mission.

How to cite: Dong, C., Wang, L., Hakim, A., Bhattacharjee, A., Slavin, J., DiBraccio, G., and Germaschewski, K.: Global Ten-Moment Multifluid Simulations of the Solar Wind Interaction with Mercury: From the Planetary Conducting Core to the Dynamic Magnetosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13186, https://doi.org/10.5194/egusphere-egu2020-13186, 2020.

EGU2020-18327 | Displays | PS1.4

Can we forecast the arrival of ICMEs for the whole Solar Systems?

Dario Del Moro, Gianluca Napoletano, Francesco Berrilli, Luca Giovannelli, Ermanno Pietropaolo, and Raffaello Foldes

Solar wind transients, i.e. interplanetary coronal mass ejections (ICMEs) drive Space Weather throughout the heliosphere and the prediction of their impact on different solar system bodies is one of the primary goals of the Planetary Space Weather forecasting. We realized a procedure based on the Drag-Based Model (Vrsnak et al., 2013, Napoletano et al. 2018) which uses probability distributions for the input parameters, and allows the evaluation of the uncertainty on the forecast. This approach has been tested against a set of ICMEs whose transit times are known, obtaining extremely promising results.

We apply this model to propagate a sample of ICMEs from their sources on the solar surface into the heliosphere. We made use of the seminal works by Prise et al. (2015), Winslow et al. (2015) and Witasse et al. (2017) who tracked the ICMEs through their journeys using data from several spacecraft.

Considering the extremely short computation time needed by the model to propagate ICMEs, this approach is a promising candidate to forecast ICME arrival to planetary bodies and spacecraft in the whole heliosphere, with relevant application to space-mission short-term planning.

How to cite: Del Moro, D., Napoletano, G., Berrilli, F., Giovannelli, L., Pietropaolo, E., and Foldes, R.: Can we forecast the arrival of ICMEs for the whole Solar Systems?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18327, https://doi.org/10.5194/egusphere-egu2020-18327, 2020.

EGU2020-20905 | Displays | PS1.4

Revisiting the Strongest Martian X-Ray Halo Observed by XMM-Newton on 2003 November 19–21

Limei Yan, Jiawei Gao, Lihui Chai, Lingling Zhao, Zhaojin Rong, and Yong Wei

On 2003 November 20–21, when the most intense geomagnetic storm during solar cycle 23 was observed at Earth, XMM-Newton recorded the strongest Martian X-ray halo hitherto. The strongest Martian X-ray halo has been suggested to be caused by the unusual solar wind, but no direct evidence has been given in previous studies. Here, based on the Mars Global Surveyor (MGS) observations, unambiguous evidence of unusual solar wind impact during that XMM-Newton observation was found: the whole induced magnetosphere of Mars was highly compressed. The comparison between the solar wind dynamic pressure estimated at Mars from MGS observation and that predicted by different solar wind propagation models suggests that the unusal solar wind is probably related to the interplanetary coronal mass ejection observed at Earth on 2003 November 20.

How to cite: Yan, L., Gao, J., Chai, L., Zhao, L., Rong, Z., and Wei, Y.: Revisiting the Strongest Martian X-Ray Halo Observed by XMM-Newton on 2003 November 19–21, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20905, https://doi.org/10.5194/egusphere-egu2020-20905, 2020.

EGU2020-3489 | Displays | PS1.4

Interplanetary effects on planetary environments: Earth, Venus, and Mercury

Monica Laurenza, Anna Milillo, Tommaso Alberti, Valeria Mangano, Stefano Massetti, Christina Plainaki, Alessandro Mura, Elisabetta De Angelis, Rosanna Rispoli, Stavro Ivanovski, and Stefano Orsini

The interplanetary and planetary environments are characterized by several intrinsic and induced properties as magnetic fields, waves and instabilites, boundaries, and ionizing radiation components. These features usually evolve on timescales ranging from seconds up to years, mainly controlled by the solar activity.

BepiColombo and Solar Orbiter flybys will offer an interesting opportunity to investigate the dynamical features of both magnetic fields and particle populations when passing from the interplanetary to the planetary environments, thus allowing us to properly characterize different regions of the interplanetary and planetary space.

This contribution discusses some outstanding features of planetary environments (Earth, Venus, and Mercury) when they interact with the interplanetary medium by considering data coming from in-flight space missions as ACE, MESSENGER, and Venus Express. Moreover, a special attention will be devoted to BepiColombo flybys which will be helpful for deeper investigations.

How to cite: Laurenza, M., Milillo, A., Alberti, T., Mangano, V., Massetti, S., Plainaki, C., Mura, A., De Angelis, E., Rispoli, R., Ivanovski, S., and Orsini, S.: Interplanetary effects on planetary environments: Earth, Venus, and Mercury, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3489, https://doi.org/10.5194/egusphere-egu2020-3489, 2020.

EGU2020-9895 | Displays | PS1.4

A detailed look on the interaction of solar wind helium with Mercury’s surface in the laboratory

Herbert Biber, Paul S. Szabo, Noah Jäggi, Martin Wallner, Reinhard Stadlmayr, Anna Niggas, Marcos V. Moro, Daniel Primetzhofer, Andreas Nenning, Andreas Mutzke, Markus Sauer, Jürgen Fleig, Annette Foelske-Schmitz, Klaus Mezger, Helmut Lammer, André Galli, Peter Wurz, and Friedrich Aumayr

EGU2020-4118 | Displays | PS1.4

Transpolar Arc Observed by the Wide-Field Auroral Imager Onboard Fengyun Satellite

Fei He, Xiao-Xin Zhang, Zhonghua Yao, Yong Wei, and Weixing Wan

Transpolar arcs that occur primarily under northward interplanetary magnetic field (IMF) are a class of auroral features in the polar cap region. Many mechanisms have been proposed to interpret the generation of the arcs, including reconnection and sudden change in the IMF. It is now generally accepted that IMF BYcomponent plays a key role in the generation and evolution of the arcs. Here we report an interesting long-lasting and moving transpolar arc observed during a geomagnetically quiet period (Dst<10 nT and AE<50 nT) by the wide-field auroral imager (WAI) onboard the Chinese Fengyun satellite. The WAI is a recently launched imager operated in far ultraviolet wavelength (LBH band in 140-180 nm) in a sun-synchronous orbit with a height of ~840 km. It is shown that the arc was initiated at the poleward auroral boundary on dawnside after the IMF turned to be northward and persisted for more than 5 hours. The arc moved toward the noon-midnight line as the IMF BYcomponent changed its direction and then moved back toward dawnside. An interesting phenomenon was that the arc was accompanied with strong energetic proton (30-80 keV) precipitations with geomagnetic latitude greater than 70° but no significant electron precipitations. However, the origin of these energetic protons is unknown and is worthy study in future.

How to cite: He, F., Zhang, X.-X., Yao, Z., Wei, Y., and Wan, W.: Transpolar Arc Observed by the Wide-Field Auroral Imager Onboard Fengyun Satellite, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4118, https://doi.org/10.5194/egusphere-egu2020-4118, 2020.

Earth’s present dipolar magnetic field extends into the interplanetary space and interacts with the solar wind, forming a magnetosphere filled up with charged particles mostly originating from the Earth’s atmosphere. In the elongated tail of the magnetosphere, the particles were observed to move either Earthward or tailward with different speeds at different locations, even outside the Moon’s orbit. We hypothesize that the lunar soil, on both the nearside and farside, should have been impacted by these particles during the geological history, and the impact was controlled by the size and morphology of the magnetosphere. We predict that the farside soil could also have the features similar to those in the nearside soil, e.g., 15N-enrichment. Furthermore, we may infer the evolution of the magnetosphere and atmosphere by examining the implanted particles in the lunar soil from both sides. This hypothesis could provide an alternative way to study the evolution of Earth’s dynamo and atmosphere.

How to cite: Wei, Y., Zhong, J., He, F., and zhang, H.: Implantation of Earth’s atmospheric ions into the nearside and farside lunar soil: implications to geodynamo evolution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7762, https://doi.org/10.5194/egusphere-egu2020-7762, 2020.

EGU2020-12469 | Displays | PS1.4

The magnetic flux transport along the -Esw direction in the magnetotails on Mars and Venus

Lihui Chai, James Slavin, Yong Wei, Weixing Wan, Charlie F. Bowers, Gina DiBraccio, Eduard Dubinin, Markus Fraenz, Willi Exner, Moritz Feyerabend, Uwe Motschmann, Kun Li, Jun Cui, and Tielong Zhang

The induced magnetotails on Mars and Venus are considered to arise through the interplanetary magnetic field (IMF) draping around the planet and the solar wind deceleration due to the mass loading effect. They have very similar structures as that on Earth, two magnetic lobes of opposite radial magnetic fields and a plasma sheet in between. However, the orientation and geometry of the induced magnetotails are controlled by the IMF, not the planetary intrinsic magnetic field. In this study, we present another characteristic of the induced magnetotails on Mars and Venus with the observations of MAVEN and Venus Express. It is found that the magnetic flux in the induced magnetotails on Mars and Venus are inhomogeneous. There is more magnetic flux in the +E hemisphere than -E hemisphere. The magnetic flux is observed to transport gradually from the +E hemisphere to the -E hemisphere along the magnetotail. The magnetotail magnetic flux transport seems to be faster on Mars than that at Venus. Based on these observations, we suggest that the finite gyro-radius effect of the planetary ions that are picked up by the solar wind is responsible to the magnetic flux inhomogeneity and transport in the induced magnetotails. The role of the magnetic pressure gradient in the magnetotail will be discussed.

How to cite: Chai, L., Slavin, J., Wei, Y., Wan, W., Bowers, C. F., DiBraccio, G., Dubinin, E., Fraenz, M., Exner, W., Feyerabend, M., Motschmann, U., Li, K., Cui, J., and Zhang, T.: The magnetic flux transport along the -Esw direction in the magnetotails on Mars and Venus, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12469, https://doi.org/10.5194/egusphere-egu2020-12469, 2020.

EGU2020-19700 | Displays | PS1.4

MoMo’s prediction of Mars’ ionosphere contribution to InSight RISE Doppler data

sebastien Le Maistre, Nicolas Bergeot, Olivier Witasse, Pierre-Louis Blelly, Wlodek Kofman, Kerstin Peter, Veronique Dehant, Jean-Marie Chevalier, and Ozgur Karatekin

The NASA InSight mission is operating from the surface of Mars for more than a year. RISE (for Rotation and Interior Structure Experiment) is one of the scientific payloads of InSight. This radio-science experiment consisting in an X-band transponder and two horn-antennas enabling two-way coherent radio-link between Mars and the Earth [Folkner et al., 2018]. The main goal of RISE is to measure the slight modulations of the nutational motion of the spin axis of Mars induced by the liquid core of the planet in order to constrain its interior structure and core properties. To increase our chance to achieve this challenging goal, we must calibrate the RISE Doppler data by accounting to 2nd order effects like the Mars atmospheric noise.

This study shows the predicted contribution of the Martian ionosphere to the RISE data collected so far. To do so, we use a new empirical model of the Mars’ ionosphere called MoMo [Bergeot et al. 2019]. This model is based on the large database of Total Electron Content (TEC) derived from the subsurface mode of the Mars Express MARSIS radar. The model provides the vertical TEC as a function of solar zenith angle, solar activity, solar longitude and the location. Using MoMo, we produce vTEC maps for Mars that are then used to estimate the slant TEC in the Earth line of sight, enabling to infer the phase delay and Doppler shift affecting the RISE X-band measurements. These computed effects are shown to be of the order of 10-3mm.s-1 in Doppler observables, with a larger effect around sunrise and sunset. This is about one order of magnitude below the typical measurement noise of RISE, but it is comparable to the contribution of the liquid core in the Doppler (~10-3-10-2mm.s-1).

The MoMo model is suitable for any Mars radio-science data calibration, and in particular the forthcoming ExoMars 2020 LaRa measurements [Dehant et al. 2019]. The predictions made with MoMo will be of great use either for the data corrections or to define the timing of observations in order to avoid operating when the TEC rapidly varies (i.e. close to sunrise and sunset). The model output is further discussed here in terms of climatologic behavior of the Mars’ ionosphere. For comparison, we also investigate the contribution of the Earth ionosphere using Global Ionospheric Maps (GIMs) based on GNSS data.

How to cite: Le Maistre, S., Bergeot, N., Witasse, O., Blelly, P.-L., Kofman, W., Peter, K., Dehant, V., Chevalier, J.-M., and Karatekin, O.: MoMo’s prediction of Mars’ ionosphere contribution to InSight RISE Doppler data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19700, https://doi.org/10.5194/egusphere-egu2020-19700, 2020.

EGU2020-6400 | Displays | PS1.4

Energetic ion dynamics near the cusp region of Mercury

Eunjin Jang, Jiutong zhao, Chao Yue, Qiugang Zong, Ying Liu, and Zhiyang Liu

Energetic ions in Mercury’s magnetosphere are very dynamic, just like in the magnetosphere of Earth. In this study, we have shown two energetic proton observations by MESSENGER near the cusp region of Mercury. For one case, we have observed large flux of energetic protons while the other case has almost no flux, indicating that the near cusp region may trap energetic particles under particular conditions. In order to understand that under what conditions the near cusp region of Mercury could trap energetic particles, we have traced the trajectories of single particle with different energies by using a modeled magnetic field, called KT17. Under different magnetic field geometry, the motions of single particle with various energies are different. The test particles can be trapped around the cusp region when the disturbance activity is strong, generating the magnetic field local minimum near the cusp region while the particles can’t be trapped and escape along the magnetic field through the dawn side cusp when there is little solar activity.

How to cite: Jang, E., zhao, J., Yue, C., Zong, Q., Liu, Y., and Liu, Z.: Energetic ion dynamics near the cusp region of Mercury, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6400, https://doi.org/10.5194/egusphere-egu2020-6400, 2020.

EGU2020-7086 | Displays | PS1.4

Reconstruction of the magnetic connection from Mercury to the solar corona

Alessandro Ippolito, Christina Plainaki, Gaetano Zimbardo, Stefano Massetti, and Anna Milillo

The magnetic foot point of Mercury on the solar disk has been reconstructed for selected case studies, in order to better understand the interaction between the solar corona and the planet. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that gives a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a “local” diffusion coefficient, which is a function of the fluctuation level and magnetic field correlation lengths. The simulation is tailored to specific events by using the observed values of solar wind velocity and magnetic fluctuation levels. Magnetic data from MAG/MESSENGER have been considered to compute the magnetic fluctuation level, while, concerning proton fluxes, FIPS/MESSENGER data has been taken into account. A number of SEP events observed on Mercury during 2011 and 2012 have been analysed, studying, for each event, the magnetic connection from Mercury to the solar corona, and the position of the active region possibly source of the accelerated particles observed.

How to cite: Ippolito, A., Plainaki, C., Zimbardo, G., Massetti, S., and Milillo, A.: Reconstruction of the magnetic connection from Mercury to the solar corona, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7086, https://doi.org/10.5194/egusphere-egu2020-7086, 2020.

EGU2020-7143 | Displays | PS1.4

Space weather at Mercury as observed by the THEMIS telescope from Earth

Melinda Dósa, Valeria Mangano, Anna Milillo, Stefano Massetti, Zsofia Bebesi, and Anikó Timár

The dynamic changes of Mercury’s Na exosphere are investigated here, in relation to space weather conditions. Sodium plays a special role in Mercury’s exosphere: due to its strong resonance D lines at 5890-95Å it has been observed and monitored by Earth-based telescopes for decades. Different and highly variable patterns of Na-emission have been identified. In addition to the release processes already studied extensively in the past, we aim here to investigate the following factors more in detail: the distance to the Sun, position in relation to the ecliptic plane and solar wind magnetic field strength and direction. In order to better investigate the relationship of these factors, we have studied the intensity of Na-emission as a function of solar wind dynamic pressure and TAA of Mercury by means of the extended dataset images collected from 2009 to 2013 by Earth-based observations performed at the THEMIS solar telescope. Solar wind velocity and density values are propagated with the magnetic lasso method to the position of Mercury from nearby space probes and compared with Na emission intensity. Data of either ACE or one of the two STEREO spacecraft were used, depending on which spacecraft had a smaller angular distance to Mercury. Single cases are studied qualitatively, and a longer-term quantitative comparison is shown, including further parameters (solar wind magnetic field strength and direction, TAA).

How to cite: Dósa, M., Mangano, V., Milillo, A., Massetti, S., Bebesi, Z., and Timár, A.: Space weather at Mercury as observed by the THEMIS telescope from Earth, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7143, https://doi.org/10.5194/egusphere-egu2020-7143, 2020.

EGU2020-1974 | Displays | PS1.4

Recent advances on magnetic reconnection and dipolarization at Saturn

Zhonghua Yao and Ruilong Guo

Magnetic reconnection and dipolarization are crucial processes in driving magnetospheric dynamics, including particle energization, mass circulation, auroral processes etc. Recent studies revealed that these processes at Saturn are fundamentally different to the ones at Earth. The reconnection and dipolarization processes are far more important than previously expected at Saturn’s dayside magnetodisc. Dayside magnetodisc reconnection was directly identified using Cassini measurements (Guo et al. 2018), and was found to be drizzle-like and rotating in Saturn’s magnetosphere (Yao et al. 2017 and Guo et al. 2019). Moreover, magnetic dipolarization could also exist at Saturn’s dayside, which is fundamentally different to the terrestrial situation (Yao et al. 2018). We here review these recent advances and their potential implications to future investigations, for example the application to Jupiter’s magnetosphere.

How to cite: Yao, Z. and Guo, R.: Recent advances on magnetic reconnection and dipolarization at Saturn, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1974, https://doi.org/10.5194/egusphere-egu2020-1974, 2020.

EGU2020-2395 | Displays | PS1.4

Interplanetary shocks at 5 AU and their effects on Jupiter's decametric radio emissions

Ezequiel Echer

EGU2020-19022 | Displays | PS1.4

Exospheric Na distributions along the Mercury orbit with the THEMIS telescope

Anna Milillo, Valeria Mangano, Stefano Massetti, alessandro Mura, christina Plainaki, Tommaso Alberti, Stavro Ivanovski, Elisabetta De Angelis, and Rosanna Rispoli

The variability of Na exosphere of Mercury shows time scales from less than one hour to seasonal variations. While the faster variations, accounting of about 10-20% of fluctuations are probably linked to the planet response to solar wind and IMF variability, the seasonal variations (up to about 80%) should be explained by a complex mechanisms involving different surface release processes, loss, source and migrations of the exospheric Na atoms. Eventually, a Na annual cycle can be identified. In the past, integrated disk emission from ground-based observations and equatorial density from MESSENGER have been analysed. In this study, for a better investigation of the exospheric Na features, we have studied the local time and latitudinal distributions of the exospheric Na column density as a function of the True Anomaly Angle (TAA) of Mercury by means of the extended dataset of images, collected from 2009 to 2013, by the THEMIS solar telescope. In particular, THEMIS images, in agreement with previous results, registered a strong general increase at aphelion and a dawn ward emission predominance with respect to dusk ward and subsolar region between 90° and 150° TAA. We find a predominance of subsolar column density along the rest of the Mercury orbit. Also an unexpected relation between Northward or Southward peak emission and both TAA and local time is evidenced by our analysis requiring further investigations. Possible relationship with distance from the dust disk or IMF polarity is being considering.

How to cite: Milillo, A., Mangano, V., Massetti, S., Mura, A., Plainaki, C., Alberti, T., Ivanovski, S., De Angelis, E., and Rispoli, R.: Exospheric Na distributions along the Mercury orbit with the THEMIS telescope , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19022, https://doi.org/10.5194/egusphere-egu2020-19022, 2020.

EGU2020-9386 | Displays | PS1.4

Combining Experiments and Modelling to Understand the Role of Potential Sputtering by Solar Wind Ions

Paul Stefan Szabo, Herbert Biber, Noah Jäggi, Matthias Brenner, David Weichselbaum, Markus Wappl, Marcos V. Moro, Anna Niggas, Reinhard Stadlmayr, Daniel Primetzhofer, Andreas Nenning, Andreas Mutzke, Markus Sauer, Jürgen Fleig, Annette Foelske-Schmitz, Klaus Mezger, Helmut Lammer, André Galli, Peter Wurz, and Friedrich Aumayr

In the absence of a protecting atmosphere, the surfaces of rocky bodies in the solar system are affected by significant space weathering due to the exposure to the solar wind [1]. Fundamental knowledge of space weathering effects, such as optical changes of surfaces as well as the formation of an exosphere is essential for gaining insights into the history of planetary bodies in the solar system [2]. Primarily the exospheres of Mercury and Moon are presently of great interest and the interpretation of their formation processes relies on the understanding of all space weathering effects on mineral surfaces.

Sputtering of refractory elements by solar wind ions is one of the most important release processes. We investigate solar wind sputtering by measuring and modelling the sputtering of pyroxene samples as analogues for the surfaces of Mercury and Moon [3, 4]. These measurements with thin film samples on Quartz Crystal Microbalance (QCM) substrates allow recording of sputtering yields in-situ and in real time [5]. For the simulation of kinetic sputtering from the ion-induced collision cascade we use the software SDTrimSP with adapted input parameters that consistently reproduce measured kinetic sputtering yields [4, 6].

This study focuses on investigating the potential sputtering of insulating samples by multiply charged ions [7]. Changes of these sputtering yields with fluence are compared to calculations with a model based on inputs from SDTrimSP simulations. This leads to a very good agreement with steady-state sputtering yields under the assumption that only O atoms are sputtered by the potential energy of the ions. The observed decreasing sputtering yields can be explained by a partial O depletion on the surface [4]. Based on these findings expected surface composition changes and sputtering yields under realistic solar wind conditions can be calculated. Our results are in line with previous investigations (see e.g. [8, 9]), creating a consistent view on solar wind sputtering effects from experiments to established modelling efforts.

 

References:

[1]          B. Hapke, J. Geophys. Res.: Planets, 106, 10039 (2001).

[2]          P. Wurz, et al., Icarus, 191, 486 (2007).

[3]          P.S. Szabo, et al., Icarus, 314, 98 (2018).

[4]          P.S. Szabo, et al., submitted to Astrophys. J. (2020).

[5]          G. Hayderer, et al., Rev. Sci. Instrum., 70, 3696 (1999).

[6]          A. Mutzke, et al., “SDTrimSP Version 6.00“, IPP Report, (2019).

[7]          F. Aumayr, H. Winter, Philos. Trans. R. Soc. A, 362, 77 (2004).

[8]          H. Hijazi, et al., J. Geophys. Res.: Planets, 122, 1597 (2017).

[9]          S.T. Alnussirat, et al., Nucl. Instrum. Methods Phys. Res. B, 420, 33 (2018).

How to cite: Szabo, P. S., Biber, H., Jäggi, N., Brenner, M., Weichselbaum, D., Wappl, M., Moro, M. V., Niggas, A., Stadlmayr, R., Primetzhofer, D., Nenning, A., Mutzke, A., Sauer, M., Fleig, J., Foelske-Schmitz, A., Mezger, K., Lammer, H., Galli, A., Wurz, P., and Aumayr, F.: Combining Experiments and Modelling to Understand the Role of Potential Sputtering by Solar Wind Ions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9386, https://doi.org/10.5194/egusphere-egu2020-9386, 2020.

Low frequency quasiperiodic (QP) magnetic field fluctuations are commonly observed in terrestrial and planetary magnetosphere.  At Earth,  these magnetohydrodynamic (MHD) waves are often observed in ultralow frequency (ULF) band (~1 mHz to 1 Hz), which could be generated by solar wind buffeting, Kelvin-Helmholtz instability and/or wave-particle interactions inside the Earth's magnetosphere. At giant planets (Saturn or Jupiter), their enormous magnetospheres often produce QP fluctuations with frequencies lower than the terrestrial ULF waves. In this study, we use Cassini spacecraft observations to analysis waves at period of 10 min to 60 min in Saturnian magnetosphere. We compare wave activities during different solar activities.

How to cite: Pan, D. and Yao, Z.: Wave activities during different phase of solar cycle : Cassini observations on Saturn, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3994, https://doi.org/10.5194/egusphere-egu2020-3994, 2020.

EGU2020-2537 | Displays | PS1.4

A wedgelet current system on Saturn

Ruilong Guo, Zhonghua Yao, Benjamin Palmaerts, William Dunn, Nick Sergis, Denis Grodent, Shengyi Ye, Zuyin Pu, Japheth Yates, Sarah Badman, and Yong Wei

Magnetic energy and mass release processes are key issues to understand the magnetospheric dynamics and aurorae processes on planets. Recent studies reveal that rotationally driven processes at dayside on giant planets are much more important than we ever expected. The discovery on the dayside magnetodisc reconnection demonstrates that the rotation effect can overcome the solar wind compression to sufficiently stretch magnetic field lines at dayside (Guo et al., 2018, doi: 10.1038/s41550-018-0461-9). A long-standing small-scale reconnection process was also shown at all local times (Guo et al., 2019, doi: 10.3847/2041-8213/ab4429). Using Cassini in situ multiple instruments data, we here proposed a wedgelet current system governing the entire magnetosphere of Saturn, which can explain the observational phenomena of quasi-periodical electron energization recurrence and beads-like structure in the main aurora region. Localized active regions with finite azimuthal lengths in the magnetosphere were discretely and azimuthally distributed along the magnetodisc and rotated with the magnetosphere. The electron energizations recurred at the spacecraft are related to each active region that passed by. These studies reveal that the dynamics in magnetodisc are global effects on giant planets, which are not always restrained at nightside.

How to cite: Guo, R., Yao, Z., Palmaerts, B., Dunn, W., Sergis, N., Grodent, D., Ye, S., Pu, Z., Yates, J., Badman, S., and Wei, Y.: A wedgelet current system on Saturn, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2537, https://doi.org/10.5194/egusphere-egu2020-2537, 2020.

EGU2020-5405 | Displays | PS1.4

Kinetic simulations of the Jovian ion circulation around Ganymede and space weather implications

Christina Plainaki, Stefano Massetti, Xianzhe Jia, Alessandro Mura, Milillo Anna, Davide Grassi, Giuseppe Sindoni, and Emiliano D'Aversa

The exosphere of Jupiter’s moon Ganymede is the interface region linking the moon’s icy surface to Jupiter’s magnetospheric environment. Space weather phenomena driven by the variability of the radiation environment within the Jupiter system can have a direct impact on the sputtering-induced exosphere of Ganymede.

In this work we simulate the Jovian ion precipitation to Ganymede’s surface for different moon orbital phases around Jupiter. In particular, we consider three different configurations between Ganymede’s magnetic field and Jupiter plasma sheet, similar to those encountered during the Galileo G2, G8, and G28 flyby (i.e., the moon above, inside, below the Jupiter plasma sheet). We discuss the differences between the various ion precipitation patterns and the implications in the density distribution of the sputtered-water exosphere of this moon. We also comment the possible relation of these ion precipitation patterns with the surface brightness asymmetries both between Ganymede’s polar cap and equatorial regions and between the leading and trailing hemispheres. The results of this preliminary analysis are relevant to the JUICE mission and in particular to the preparation of the future observation strategies for the environment of Ganymede.

How to cite: Plainaki, C., Massetti, S., Jia, X., Mura, A., Anna, M., Grassi, D., Sindoni, G., and D'Aversa, E.: Kinetic simulations of the Jovian ion circulation around Ganymede and space weather implications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5405, https://doi.org/10.5194/egusphere-egu2020-5405, 2020.

PS2.1 – Small Bodies Open (Asteroids, Comets, Meteoroids, and Dust)

EGU2020-3685 | Displays | PS2.1

The partitioning of the inner and outer solar system by a structured protoplanetary disk

Ramon Brasser and Stephen Mojzsis

Mass-independent isotopic anomalies in planets and meteorites define two cosmochemically distinct regions: the carbonaceous and non-carbonaceous meteorites, implying that the non-carbonaceous (terrestrial) and carbonaceous (jovian) reservoirs were kept separate during and after planet formation. The iron meteorites show a similar dichotomy.

The formation of Jupiter is widely invoked to explain this compositional dichotomy by acting as an effective barrier between the two reservoirs. Jupiter’s solid kernel possibly grew to ~20 Mearth in ~1 Myr from the accretion of sub meter-sized objects (termed “pebbles”), followed by slower accretion via planetesimals. Subsequent gas envelope contraction is thought to have led to Jupiter’s formation as a gas giant.

We show using dynamical simulations that the growth of Jupiter from pebble accretion is not fast enough to be responsible for the inferred separation of the terrestrial and jovian reservoirs. We propose instead that the dichotomy was caused by a pressure maximum in the disk near Jupiter’s location, which created a ringed structure such as those detected by the Atacama Large Millimeter/submillimeter Array(ALMA). One or multiple such long-lived pressure maxima almost completely prevented pebbles from the jovian region reaching the terrestrial zone, maintaining a compositional partition between the two regions. We thus suggest that our young solar system’s protoplanetary disk developed at least one and likely multiple rings, which potentially triggered the formation of the giant planets [1].


[1] Brasser, R. and Mojzsis, S.J. (2020) Nature Astronomy doi: 10.1038/s41550-019-0978-6

How to cite: Brasser, R. and Mojzsis, S.: The partitioning of the inner and outer solar system by a structured protoplanetary disk, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3685, https://doi.org/10.5194/egusphere-egu2020-3685, 2020.

EGU2020-9973 | Displays | PS2.1

Statistics of Saturn Ring occultations

Larry W. Esposito, Miodrag Sremcevic, Joshua E Colwell, and Stephanie Eckert

We give calculations for the excess variance, excess skewness and excess kurtosis with formulas that combine the effects of cylindrical shadows, along with gaps, ghosts and clumps (all calculated for the granola bar model for rectangular clumps and gaps). Wherever the rings have significant gaps or clumps, those will dominate the statistics over the individual ring particles contribution. We have refined an overlap correction for multiple shadows, which is important for larger optical depth. This correction results from summing a geometric series, and is similar to the empirical formula, eq. (22) in Colwell et al (2018). The comparison to Monte Carlo calculations is improved for large particle size by including the edge effects when large particles cross the edges of the viewing area A in Cassini UVIS occultations. As a check, we can explain the upward curvature of the dependence of normalized excess variance for Saturn’s background C ring by the observation of Jerousek etal (2018) that the increased optical depth is directly correlated with effective particle size. Assuming a linear dependence Reff = 12 * (tau – 0.08) + 1.8m, we match both the curvature of excess variance E and the skewness Gamma in the region between 78,000 and 84,600km from Saturn. This explanation requires no gaps or ghosts (Baillie etal 2013) in this region of Saturn’s C ring.

How to cite: Esposito, L. W., Sremcevic, M., Colwell, J. E., and Eckert, S.: Statistics of Saturn Ring occultations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9973, https://doi.org/10.5194/egusphere-egu2020-9973, 2020.

EGU2020-6899 | Displays | PS2.1

Carbon-rich composition of the icy moons of Jupiter and Saturn, and asteroid 1-Ceres

Bruno Reynard, Adrien Neri, François Guyot, and Christophe Sotin

The inner structure of icy moons comprises ices, liquid water, a silicate rocky core and sometimes an inner metallic core depending on thermal evolution and differentiation. Mineralogy and density models for the silicate part of the icy satellites cores were assessed assuming a carbonaceous chondritic (CI) bulk composition and using a free-energy minimization code and experiments [1]. Densities of other components, solid and liquid sulfides, carbonaceous matter, were evaluated from available equations of state. Model densities for silicates are larger than assessed from magnesian terrestrial minerals, by 200 to 600 kg/m3 for the hydrated silicates, and 300 to 500 kg/m3 for the dry silicates, due to the lower iron bulk concentration in terrestrial silicates as a lot of iron is segregated in the core.

We find that CI density models of icy satellite cores taking into account only the silicate and metal/sulfide fraction cannot account for the observed densities and reduced moment of inertia of Titan and Ganymede without adding a lower density component. We propose that this low-density component is carbonaceous matter derived from insoluble organic matter, in proportion of ~30-40% in volume and 15-20% in mass. This proportion is compatible with contributions from CI and comets, making these primitive bodies including their carbonaceous matter component likely precursors of icy moons, and potentially of most of the objects formed behind the snow line of the solar system. Similar conclusions are reached for 1-Ceres when applying this compositional model, with even higher carbon content of the order of 25±5wt% in line with independent estimates [2]. It suggests that the building materials are similar for asteroid 1-Ceres and the icy moons of giant planets.

 

[1]Neri et al., Earth Planet Sci Letters, 530 (2020) 115920

[2]Zolotov, Icarus, 335 (2020) 113404

How to cite: Reynard, B., Neri, A., Guyot, F., and Sotin, C.: Carbon-rich composition of the icy moons of Jupiter and Saturn, and asteroid 1-Ceres, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6899, https://doi.org/10.5194/egusphere-egu2020-6899, 2020.

EGU2020-4679 | Displays | PS2.1

Thermal and porosity properties of meteorites: A compilation of published data and new measurements

Assi-Johanna Soini, Ilmo Kukkonen, Tomas Kohout, and Arto Luttinen

We report direct measurements of thermal diffusivity and conductivity at room temperature for 38 meteorite samples of 36 different meteorites including mostly chondrites, and thus almost triple the number of meteorites for which thermal conductivity is directly measured. Additionally, we measured porosity for 34 of these samples. Thermal properties were measured using optical infrared scanning method on samples of cm-sizes with a flat, sawn surface.

    A database compiled from our measurements and literature data suggests that thermal diffusivities and conductivities at room temperature vary largely among samples even of the same petrologic and chemical type and overlap among e.g. different ordinary chondrite classes. Measured conductivities of ordinary chondrites vary from 0.4 to 5.1 W/m/K. On average, enstatite chondrites show much higher values (2.33 – 5.51 W/m/K) and carbonaceous chondrites lower values (0.5 – 2.55 W/m/K).

    Mineral composition (silicates vs. iron-nickel) and porosity control conductivity. Porosity shows (linear) negative correlation with conductivity. Variable conductivity is attributed to heterogeneity in mineral composition and porosity by intragranular and intergranular voids and cracks, which are important in the scale of typical meteorite samples. The effect of porosity may be even more significant for thermal properties than that of the metal content in chondrites.

 

Reference

Soini A.-J., Kukkonen I. T., Kohout T., and Luttinen A. (accepted for publication). Thermal and porosity properties of meteorites: A compilation of published data and new measurements. Meteoritics & Planetary Science.

How to cite: Soini, A.-J., Kukkonen, I., Kohout, T., and Luttinen, A.: Thermal and porosity properties of meteorites: A compilation of published data and new measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4679, https://doi.org/10.5194/egusphere-egu2020-4679, 2020.

EGU2020-15089 | Displays | PS2.1 | Highlight

The Latest (Dusty) Pieces in the Rosetta Story

Stavro Lambrov Ivanovski

The ESA’s Rosetta spacecraft had the unique opportunity to follow comet 67P/Churyumov-Gerasimenko (hereafter 67P) for about 2.5 years – from January 2014 to September 2016 – observing how the comet evolved while approaching the Sun, passing through perihelion and then moving back into the outer solar system. Remote sensing and in-situ instruments onboard Rosetta acquired data to study the comet’s dust environment during the entire duration of the mission, while telescopes followed the large-scale coma and tails from Earth. Here we report the latest advances of the ongoing multi-instrument approach that the Rosetta dust working group has been following in the recent years. Individual instrument data analyses have been carried on providing a first characterization of 67P dust environment. Timely, multi-instruments data analyses are now progressing a step forward in understanding how comet works and are providing critical results for a more comprehensive and unified knowledge of cometary dust environments. We will illustrate the progress we have made and the results we have reached following this constructive and collaborative approach.

We also discuss the latest achievements on the cometary dust modelling using the multi-instrument Rosetta data. In particular, what additional information these calibrated dust models provide and what we are still missing in cometary dust characterization.

How to cite: Ivanovski, S. L.: The Latest (Dusty) Pieces in the Rosetta Story, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15089, https://doi.org/10.5194/egusphere-egu2020-15089, 2020.

EGU2020-8393 | Displays | PS2.1

The spatial distribution of dust in the inner comae of comets: Evidence for and modelling of nightside emission

Nicolas Thomas, Selina-Barbara Gerig, Olga Pinzon, Raphael Marschall, Jong-Shinn Wu, and Clemence Herny

Spacecraft imaging of the inner comae of 1P/Halley (Giotto/HMC) and 19P/Borrelly (DS1/MICAS) indicated unexpectedly low ratios for the dust brightness above the dayside hemisphere to that above the nightside. Neither ratio was consistent with dust emission being directly proportional to sublimation loss of H2O using purely insolation-driven models. The near-terminator observations of 67P/Churyumov-Gerasimenko from Rosetta allow very precise separation of the dayside and nightside hemispheres and confirm low dayside to nightside dust brightness ratios. In the case of 67P values of ~3.3:1 were observed and an interesting trend towards increased ratios with decreasing heliocentric distance. Detailed modelling using insolation-driven models do not fit the data by factors of several. Dust from the dayside may contribute to the brightness on the nightside if particles are not escaping and therefore gravitationally bound. However, the radial distribution of brightness on the nightside is inconsistent with this interpretation as can be demonstrated with a simple model. The source is also not in the form of single nightside (e.g. “sunset”) jets. Furthermore, shadowing of emitted dust by the nucleus itself indicates that much of the observed brightness on the nightside is very close to the nucleus and distributed roughly uniformly around in the nightside hemisphere (Gerig et al., submitted).

Gas emission from the nightside has been a consistent element of source distributions (e.g. Bieler et al., 2015) required to model ROSINA/COPS data. However, the composition is frequently not specified. We have been investigating self-consistent, physically generated, numerical models of combined H2O and CO2 emission (see also Herny et al., submitted). Dust emission has been incorporated into the model chain allowing modelling of the observation of the gas composition, the gas density, and the dust brightness distribution in the vicinity of the nucleus for specific times. The results of investigation will be presented.

How to cite: Thomas, N., Gerig, S.-B., Pinzon, O., Marschall, R., Wu, J.-S., and Herny, C.: The spatial distribution of dust in the inner comae of comets: Evidence for and modelling of nightside emission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8393, https://doi.org/10.5194/egusphere-egu2020-8393, 2020.

EGU2020-2617 | Displays | PS2.1

The ROSINA Perspective on the CN/HCN Ratio at Comet 67P/Churyumov-Gerasimenko

Nora Hänni, Kathrin Altwegg, and Martin Rubin

The origin of cyano (CN) radicals in comets presents a long-standing riddle to the science community. Remote observations, e.g. reviewed by Fray et al. [1], show that for some comets the scale lengths, production rates, and spatial distributions of hydrogen cyanide (HCN) and CN using a Haser-based model are not consistent. Consequently, a process additional to photolysis of HCN seems to be required to explain the observed CN densities. Possible scenarios include (1) degradation of CN-producing refractories (e.g. HCN-polymers, tholins, or ammonium salts [2-3]) and (2) photolysis of other gaseous CN-bearing parent species (e.g. HC3N or C2N2).

The CN/HCN ratio observed in the inner coma of comet 67P/Churyumov-Gerasimenko with the Double Focusing Mass Spectrometer DFMS, part of the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) sensor package [4] onboard ESA’s Rosetta spacecraft, is not compatible with fragmentation of HCN under electron impact ionization. Even though from fragmentation a constant CN/HCN ratio of about 0.15 [5-7] is expected, the observed values range from almost 0.4 at the beginning of the mission (August 2014) to about 0.15 shortly after perihelion passage (August 2015). Towards the end of the mission (September 2016), CN/HCN ratios increase again. This presentation will discuss the data from ROSINA/DFMS in detail and present laboratory-based indications that direct production of CN from sublimating ammonium cyanide (NH4CN) occurs, leading to increased CN/HCN ratios. Could this be the process generating a surplus of CN radicals with respect to photolysis of HCN in certain comets?

 

 

[1] N. Fray et al. The origin oft he CN radical in comets: A review from observations and models Planetary and Space Science 53 (2005) 1243-1262.

[2] N. Hänni et al. Ammonium Salts as a Source of Small Molecules Observed with High-Resolution Electron-Impact Ionization Mass Spectrometry. J. Phys. Chem. A 123 (2019) 27, 5805-5814.

[3] K. Altwegg et al. Evidence of ammonium salts in comet 67P as explanation for the nitrogen depletion in cometary comae. Nat. Astron. (2019) in print.

[4] H. Balsiger et al. Rosina - Rosetta Orbiter Spectrometer for Ion and Neutral Analysis. Space Science Reviews 128 (2007) 745-801.

[5] S.E. Steins in NIST Chemistry WebBook, NIST Standard Reference Database Number 69, Eds. P.J. Linstrom and W.G. Mallard, National Institute of Standards and Technology, (2018).

[6] P. Kusch et al. The Dissociation of HCN, C2H2, C2N2, and C2H4 by Electron Impact. Phys. Rev. 52 (1937) 843-854.

[7] D. P. Stevenson. Ionization and Dissociation by Electron Impact: Cyanogen, Hydrogen Cyanide, and Cyanogen Chloride and the Dissociation Energy of Cyanogen. J. Chem. Phys. 18 (1950) 1347-1351.

How to cite: Hänni, N., Altwegg, K., and Rubin, M.: The ROSINA Perspective on the CN/HCN Ratio at Comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2617, https://doi.org/10.5194/egusphere-egu2020-2617, 2020.

EGU2020-20089 | Displays | PS2.1

What does really happen in a dust impact?

Sascha Kempf, William Goode, Ralf Srama, and Frank Postberg

Our current understanding of the solar system’s micrometeoroid environment relies to a substantial extent on in-situ data acquired by impact ionization dust detectors such as Ulysses’ and Galileo’s DDS or Cassini’s CDA. Such detectors derive the mass and speed of striking dust particles from the properties and evolution of the plasma created upon impact. In particular, empirical evidence suggests that the impact speed is a function of the duration of impact charge delivery onto the target - the so-called plasma rise time. Often, this dependence has been attributed to secondary impacts of target and projectile ejecta. 

During recent years the capabilities of laboratory impact detectors have been significantly improved. In particular we now have ample evidence that secondary ejecta impacts are not responsible for the rise-time dependence. In fact the plasma rise-time is rather related to the ionization of target contaminants in the vicinity of the impact site. 

In this talk we present new experimental data obtained with state-of-the-art impact ionization mass spectrometers, which shed new light on what is really going on during a hypervelocity dust impact. We further discuss the implications for the interpretation of dust data obtained with previous generations of impact ionization detectors.

How to cite: Kempf, S., Goode, W., Srama, R., and Postberg, F.: What does really happen in a dust impact?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20089, https://doi.org/10.5194/egusphere-egu2020-20089, 2020.

EGU2020-1805 | Displays | PS2.1

Dust detection by antenna instruments

Zoltan Sternovsky, Ming-Hsueh Shen, Michael DeLuca, Åshild Fredriksen, Mihály Horányi, Sean Hsu, Samuel Kočiščák, David Malaspina, Libor Nouzák, and Shengyi Ye

Antenna instruments on space missions have been used to detect dust particles and characterize dust populations. The antennas register the transient electric signal generated by the expansion of the impact plasma from the dust impact on the spacecraft body or the antenna. Given the large effective sensitive area, antenna instruments offer an advantage over dedicated dust detectors for dust populations with low fluxes. The dust accelerator facility operated at the University of Colorado has been employed to investigate the physical mechanisms of antenna signal generation. The dominant mechanism is related to the charging of the spacecraft (or antenna) by collecting some fraction of electrons and ions from the impact plasma. We have carried out a number of experimental campaigns in order to characterize the dust impact charge yields from relevant materials, the effective temperatures of dust impact plasmas, and variations of the antenna signals with spacecraft potential, or magnetic field. Here we report on a physical model that provides a good qualitative and quantitative description of the antenna waveforms recorded in laboratory conditions. The model is based on the separation of the electrons from the ions in the impact plasma and their different timescales of expansion. The escaping and collected fractions of charges are driven by the spacecraft potential. Fitting the model to the laboratory data revealed that the electrons in the impact plasma have an isotropic distribution, while ions are dominantly moving away from the dust impact location. Identifying the fine details in the antenna signals requires a relatively high sampling rate and thus not commonly resolved for past instruments. The high-rate mode of the FIELDS instrument on the Parker Solar Probe, however, can be used to verify the proposed model.

How to cite: Sternovsky, Z., Shen, M.-H., DeLuca, M., Fredriksen, Å., Horányi, M., Hsu, S., Kočiščák, S., Malaspina, D., Nouzák, L., and Ye, S.: Dust detection by antenna instruments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1805, https://doi.org/10.5194/egusphere-egu2020-1805, 2020.

EGU2020-4160 | Displays | PS2.1

The Effects of Hyperbolic Meteoroids from Parker Solar Probe to the Moon

Jamey Szalay, Petr Pokorny, Mihaly Horanyi, Stuart Bale, Eric Christian, Keith Goetz, Katherine Goodrich, Matthew Hill, Marc Kuchner, Rhiannon Larsen, David Malaspina, David McComas, Donald Mitchell, Brent Page, and Nathan Schwadron

The zodiacal cloud in the inner solar system undergoes continual evolution, as its dust grains are collisionally ground and sublimated into smaller and smaller sizes. Sufficiently small (~<500 nm) grains known as beta-meteoroids are ejected from the inner solar system on hyperbolic orbits under the influence of solar radiation pressure. These small grains can reach significantly larger speeds than those in the nominal zodiacal cloud and impact the surfaces of airless bodies. Since the discovery of the Moon's asymmetric ejecta cloud, the origin of its sunward-canted density enhancement has not been well understood. We propose impact ejecta from beta-meteoroids that hit the Moon's sunward side could explain this unresolved asymmetry. The proposed hypothesis rests on the fact that beta-meteoroids are one of the few truly asymmetric meteoroid sources in the solar system, as unbound grains always travel away from the Sun and lack a symmetric inbound counterpart. This finding suggests beta-meteoroids may also contribute to the evolution of other airless surfaces in the inner solar system as well as within other exo-zodiacal disks. We will also highlight recent observations from the Parker Solar Probe (PSP) spacecraft, which suggest it is being bombarded by the very same beta-meteoroids. We discuss how observations by PSP, which lacks a dedicated dust detector, can be used to inform the structure and variability of beta-meteoroids in the inner solar system closer to the Sun than ever before.

How to cite: Szalay, J., Pokorny, P., Horanyi, M., Bale, S., Christian, E., Goetz, K., Goodrich, K., Hill, M., Kuchner, M., Larsen, R., Malaspina, D., McComas, D., Mitchell, D., Page, B., and Schwadron, N.: The Effects of Hyperbolic Meteoroids from Parker Solar Probe to the Moon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4160, https://doi.org/10.5194/egusphere-egu2020-4160, 2020.

EGU2020-20056 | Displays | PS2.1

Parker Solar Probe Observations of a Dust Trail in the Orbit of 3200 Phaethon

Karl Battams, Guillermo Stenborg, Russell Howard, Brendan Gallagher, Matthew Knight, and Michael Kelley

We present details on the first white-light detection of a dust trail following the orbit of asteroid 3200 Phaethon, seen in images recorded by the Wide-field Imager for Parker Solar Probe (WISPR) instrument on the NASA Parker Solar Probe (PSP) mission. In this talk we will present a brief introduction to the PSP mission and the WISPR instrument. We will then show observations returned by WISPR in multiple perihelion 'encounters' that clearly show a diffuse dust trail perfectly aligned with the perihelion portion of the orbit of 3200 Phaethon, recorded while the asteroid itself was near aphelion. We will discuss the physical parameters that we have derived for the dust trail, including its visual magnitude, surface brightness and mass. We also speculate on the relationship of this trail to the Geminid meteor shower, of which Phaethon is assumed to be the parent, and demonstrate why the trail has not been detected visually until now, despite a number of dedicated observing campaigns. We also hope to present initial analyses of the most recent set of WISPR observations (January 2020), where we anticipate the trail should again be visible in the WISPR observations.

How to cite: Battams, K., Stenborg, G., Howard, R., Gallagher, B., Knight, M., and Kelley, M.: Parker Solar Probe Observations of a Dust Trail in the Orbit of 3200 Phaethon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20056, https://doi.org/10.5194/egusphere-egu2020-20056, 2020.

EGU2020-20135 | Displays | PS2.1 | Highlight

White-light observations of features in the Zodiacal dust cloud from within the solar corona

Russell Howard, Guillermo Stenborg, Phil Hess, Brendan Gallagher, and Karl Battams

The Parker Solar Probe (PSP) mission has completed four solar encounters, observing the solar corona from distances significantly closer to the Sun than from previous missions (to 36 solar radii during the first three perihelia and to 28 solar radii during the fourth). During these encounters, the Wide-field Imager for Solar Probe (WISPR) onboard PSP has been observing the F-corona/Zodiacal light - probing the dust environment in the solar corona as PSP moves through the corona. This allowed WISPR to find 1) a gradual decrease of the expected brightness of the F-corona for distances shorter than about 0.1 AU, 2) dust trails of short-period asteroid/cometary objects (e.g., 3200 Pheathon and 2P/Encke) and 3) a changing rate of dust impacts on the S/C throughout the encounter period. In this presentation, we will present these findings, discuss their nature, and elaborate on the novelty of these results. The authors acknowledge support from the NASA Parker Solar Probe program.

How to cite: Howard, R., Stenborg, G., Hess, P., Gallagher, B., and Battams, K.: White-light observations of features in the Zodiacal dust cloud from within the solar corona, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20135, https://doi.org/10.5194/egusphere-egu2020-20135, 2020.

EGU2020-12800 | Displays | PS2.1

Didymos Gravity Science through Ground-based and Satellite-to-Satellite Doppler Tracking

Paolo Tortora, Igor Gai, Marco Lombardo, Marco Zannoni, Ian Carnelli, Michael Kueppers, Paolo Martino, and Patrick Michel

Hera is ESA’s contribution to an international effort supported by ESA and NASA named Asteroid Impact and Deflection Assessment (AIDA). NASA’s DART mission will first perform a kinetic impact on Didymos secondary, nicknamed Didymoon, then Hera will follow-up with a detailed post-impact survey, to fully characterize this planetary defense technique. Two CubeSats will be deployed by the Hera spacecraft once the Early Characterization Phase has completed.

The Hera spacecraft communicates with the ground station on the Earth by means of a standard two-way X-band system. The microwave signal is sent to the S/C from a ground antenna and coherently retransmitted back to Earth, where Doppler (the key observable for gravity science) and range measurements are obtained. In addition, Hera will track the two CubeSats by means of a space-to-space inter-satellite link (ISL). This represents a very nice add-on to the gravity investigation carried out by means of Hera tracking observables as the Doppler effect that affects the inter-satellite link contains the information on the dynamics of the system, i.e. masses and gravity field of Didymos primary and secondary.

We describe here the mission scenario for the gravity science experiments to be jointly carried out by the three mission elements, i.e. Hera, CubeSat#1 (named Juventas) and CubeSat#2, via Ground-based and Satellite-to-Satellite Doppler Tracking. Also, our results and achievable accuracy for the estimation of the mass and gravity field of Didymos primary and secondary are presented.

How to cite: Tortora, P., Gai, I., Lombardo, M., Zannoni, M., Carnelli, I., Kueppers, M., Martino, P., and Michel, P.: Didymos Gravity Science through Ground-based and Satellite-to-Satellite Doppler Tracking, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12800, https://doi.org/10.5194/egusphere-egu2020-12800, 2020.

EGU2020-22173 | Displays | PS2.1

A Summary and Update on NASA’s Planetary Defense Program.

Doris Daou and Lindley Johnson

NASA and its partners maintain a watch for near-Earth objects (NEOs), asteroids and comets that pass within Earth’s vicinity, as part of an ongoing effort to discover, catalog, and characterize these bodies and to determine if any pose an impact threat. NASA’s Planetary Defense Coordination Office (PDCO) is responsible for:

  • Ensuring the early detection of potentially hazardous objects (PHOs) – asteroids and comets whose orbits are predicted to bring them within 0.05 astronomical units of Earth's orbit; and of a size large enough to reach Earth’s surface – that is, greater than perhaps 30 to 50 meters;
  • Tracking and characterizing PHOs and issuing warnings about potential impacts;
  • Providing timely and accurate communications about PHOs; and
  • Performing as a lead coordination node in U.S. Government planning for response to an actual impact threat.

 

NASA’s current congressionally-mandated objective is to detect, track, and catalogue at least 90 percent of NEOs equal to or greater than 140 meters in size by 2020, and characterize the physical properties of a subset representative of the entire population. This mandate will likely not be met given current resources dedicated to the task; however significant progress is being made.

In this paper, we will report on the status of our program and the missions working to support our planetary defense coordination office. In addition, we will provide the latest detections and characterizations results. Our office continues to work diligently with our international partners to achieve our goals and continue to safeguard Earth with the latest technologies available.

How to cite: Daou, D. and Johnson, L.: A Summary and Update on NASA’s Planetary Defense Program., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22173, https://doi.org/10.5194/egusphere-egu2020-22173, 2020.

EGU2020-20885 | Displays | PS2.1

Thermal modeling of the binary asteroid Didymos

Özgür Karatekin, Gregoire Henry, Elodie Gloesener, and Bart van Hove

The target of the ESA’s HERA mission is asteroid 65803 Didymos (1996 GT), an Apollo-type near-Earth object (NEO). Didymos is a binary asteroid; the primary body has a diameter of around 775 m and a rotation period of 2.26 hours, whereas the secondary body (informally called Didymoon) has a diameter of around 165 m and rotates around the primary at a distance of around 1.2 km in around 12 hours.

Thermophysical properties of the uppermost surface govern the exchange of radiative energy between the asteroid and its environment, hence determine surface and subsurface temperatures.  These thermophysical properties are characterized by grain size, porosity, or packing of the surface materials.  Diurnal change in surface temperature show large variations in fine soils like sand and highly porous rock with low thermal inertia, and much smaller variations in in dense rock with high thermal inertia. Here we present a thermophysical model of Didymoon based on known, assumed and derived range of physical properties.  A parameter study has been carried out for surface temperatures assuming possible thermal inertia ranges.  

Results from this study are used to investigate performance for Thermal Infrared instrument TIRA onboard HERA spacecraft. Hera is the European contribution to an international double-spacecraft collaboration. Due to launch in 2024, Hera would travel to the binary asteroid system. TIRA onboard HERA will be operating in the 8-14 µm wavelength range. It will be used for scientific analysis and to demonstrate the feasibility of using a TIR camera for GNC (Guidance, navigation and control). The main scientific output for TIRA is to determine the thermal inertia and thus the properties of the surface material.

How to cite: Karatekin, Ö., Henry, G., Gloesener, E., and van Hove, B.: Thermal modeling of the binary asteroid Didymos, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20885, https://doi.org/10.5194/egusphere-egu2020-20885, 2020.

EGU2020-19957 | Displays | PS2.1

Low Frequency Radar (LFR) on the JUVENTAS CubeSat for HERA / ESA mission

Alain Herique, Dirk Plettemeier, Wlodek Kofman, Yves Rogez, and Hannah Goldberg

The Low Frequency Radar (LFR) on the JUVENTAS CubeSat for HERA / ESA mission to Didymos Binary Asteroid is a unique opportunity to perform direct measurements of its internal structure and regolith. LFR has been developed to fathom asteroid from a small platform. This instrument is inherited from CONSERT/Rosetta and has been redesigned in the frame of the AIDA and HERA ESA mission.

Onboard JUVENTAS, LFR is operating in monostatic mode to probe down to the first hundreds of meters into the subsurface and to achieve a full tomography of the Didymos' moonlet. Direct observations of the internal structure of asteroids can solve still open basic questions like: Is the body a monolithic piece of rock or a rubble-pile? How high is the porosity? What is the typical size of the constituent blocks? Are these blocks homogeneous or heterogeneous? How is the regolith covering its surface constituted?

The low frequency aboard the Juventas CubeSat will contribute to the solution of these open and for planetary defense crucial questions.
- The first LRF objective is the characterization of the moonlet interior, to identify internal structure and to analyze the size distribution and heterogeneity of constitutive blocks from sub metric to global
- The second objective is the estimation of average permittivity and mapping of its spatial variation especially in the crater area.
- The same characterization applied to the main of the binary system is among secondary objectives.
- Supporting shape modeling and determination of the dynamical state by radar ranging is a further secondary objective.

This paper will present the instrument concept and measurement strategy, its performances and the expected science return.

How to cite: Herique, A., Plettemeier, D., Kofman, W., Rogez, Y., and Goldberg, H.: Low Frequency Radar (LFR) on the JUVENTAS CubeSat for HERA / ESA mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19957, https://doi.org/10.5194/egusphere-egu2020-19957, 2020.

EGU2020-18758 | Displays | PS2.1

Deciphering compositional processes in inner airless bodies of our Solar System

Francesca Zambon, Federico Tosi, Sébastien Besse, Rosario Brunetto, Cristian Carli, Jean-Philippe Combe, Olivier Forni, Rachel Klima, Katrin Krohn, David Rothery, Katrin Stephan, Kerri Donaldson-Hanna, Oceane Barraud, and Jacopo Nava

Over the last decades, the exploration of our Solar System carried out by automatic probes allowed a huge leap in our understanding of the planets, their main satellites and minor bodies such as asteroids and comets. However, despite the large number of diverse datasets available nowadays, comparative studies of different bodies are still poorly addressed in several cases, in particular for airless bodies.

The primary goal of our two-year project, selected in the framework of the “ISSI/ISSI-BJ Joint Call for Proposals 2019 for International Teams in Space and Earth Sciences”, is to quantify similarities and differences in the surface mineralogy of Vesta, Mercury and the Moon, substantially enhancing the scientific return of individual instrumental datasets and/or individual space missions. Here, we give an overview of our project, we clarify what is the status after the first team meeting held in March 2020.

Our project focuses on two specific questions:

Our overall approach is to apply various techniques of analysis on hyper- and multispectral data sets that are publicly available, such as those on acquired by the Dawn mission at Vesta, MESSENGER datasets obtained at Mercury and Chandrayaan-1 data for the Moon.

This work is supported by the International Space Science Institute (ISSI) and by INAF-IAPS.

How to cite: Zambon, F., Tosi, F., Besse, S., Brunetto, R., Carli, C., Combe, J.-P., Forni, O., Klima, R., Krohn, K., Rothery, D., Stephan, K., Donaldson-Hanna, K., Barraud, O., and Nava, J.: Deciphering compositional processes in inner airless bodies of our Solar System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18758, https://doi.org/10.5194/egusphere-egu2020-18758, 2020.

EGU2020-8598 | Displays | PS2.1

The Santa Rosa Meteorite from Colombia: An example of critical raw materials in a meteorite

Franziska D.H. Wilke, Barbara Bsdok, Uwe Altenberger, and Ana E. Concha

Meteorites, especially the undifferentiated ones like primitive chondrites, provide information about the origin and initial conditions of the solar system since they contain presolar and solar nebula materials (Scott, 2007). Differentiated meteorites like iron meteorites play a distinct role in constraining the early phases of planetary accretion (Yang et al. 2007). They also provide the possibility to receive information about core properties and planetary bodies. In addition to the gain in such fundamental scientific knowledge both types are of interest for the exploration of critical and precious elements (CRMs).

In the future, the tremendous increase of the consumption of these elements from terrestrial deposits and the subsequent shortage could lead to an exploitation of extra-terrestrial deposits. Therefore, “space-mining” of near Earth objects could be used as alternative source of raw materials (Ross, 2001).

While improving the characterization and classification of the Santa Rosa de Viterbo Iron Meteorite, we found notable concentrations of Au and Ge alongside major elements such as Fe, Ni and Co in the bulk composition of that meteorite. Major and rock-forming minerals such as kamacite and taenite incorporate hundreds of ppm of Ge whereas schreibersite, itself a minor component in that particular meteorite, is a source for Au. In kamacite and taenite also Ir and Ga were found in minor amounts.

 

Scott, E. R. (2007). Chondrites and the protoplanetary disk. Annu. Rev. Earth Planet. Sci., 35, 577-620.

Ross, S. D. (2001). Near-earth asteroid mining. Space, 1-24.

Yang, J., Goldstein, J. I., & Scott, E. R. (2007). Iron meteorite evidence for early formation and catastrophic disruption of protoplanets. Nature, 446(7138), 888.

 

How to cite: Wilke, F. D. H., Bsdok, B., Altenberger, U., and Concha, A. E.: The Santa Rosa Meteorite from Colombia: An example of critical raw materials in a meteorite, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8598, https://doi.org/10.5194/egusphere-egu2020-8598, 2020.

EGU2020-5144 | Displays | PS2.1

Modification of cometesimal interiors by early thermal evolution and collisions

Martin Jutzi and Gregor Golabek

In the early solar system radiogenic heating by 26Al and collisions are the two prominent ways expected to modify the internal composition of cometesimals, building blocks of comets, by removing highly volatile compounds like CO, COand NH3. However, observations indicate that even large comets like Hale-Bopp (R ≈ 70 km) can be rich in these highly volatile compounds [1].

Here we constrain under which conditions cometesimals experiencing both internal heating and collisions can retain pristine interiors. For this purpose, we employ both the state-of-the-art finite-difference marker-in-cell code I2ELVIS [2] to model the thermal evolution in 2D infinite cylinder geometry and a 3D SPH code [3] to study the interior heating caused by collisions among cometesimals. For simplicity we assume circular porous cometesimals with a low density ( ≈ 470 kg/m3) based on measurements for comet 67P/Churyumov-Gerasimenko [4].

For the parameter study of the thermal history we vary (i) cometesimal radii, (ii) formation time and the (iii) the silicate/ice ratio. For the latter we keep the mean density fixed and change the porosity of the cometesimal. For the impact models we use porous, low-strength objects and vary (i) target and (ii) projectile radii, (iii) impact velocity as well as (iv) impact angle. Potential losses of volatile compounds from their interiors are calculated based on their critical temperatures taken from literature [5]. Our combined results indicate that only small or late-formed cometesimals remain mostly pristine, while early formed objects can even reach temperatures high enough to melt the water ice.

 

REFERENCES

[1] Biver et al., Nature 380, 137-139 (1996).

[2] Gerya & Yuen, Phys. Earth Planet. Int. 163, 83-105 (2007).

[3] Jutzi, Planet. Space Sci. 107, 3–9 (2015).

[4] Sierks et al. Science 347, 1044 (2015).

[5] Davidsson et al. Astronomy & Astrophysics 592, A63 (2016).

How to cite: Jutzi, M. and Golabek, G.: Modification of cometesimal interiors by early thermal evolution and collisions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5144, https://doi.org/10.5194/egusphere-egu2020-5144, 2020.

EGU2020-5711 | Displays | PS2.1

The Rosetta Science Archive: Closing Out the Science Content

David Heather, Diego Fraga, Laurence O'Rourke, and Matt Taylor

On 30 September 2016, Rosetta completed its mission by landing on comet 67P/Churyumov-Gerasimenko. Although this marked an end to the spacecraft’s operations, intensive work has continued for several years, with the instrument teams updating their data in response to scientific reviews and delivering them to ESA’s Planetary Science Archive (PSA). ESA has also been working with the instrument teams to produce new and enhanced data, and to improve documentation, aiming to provide the best long-term archive possible for the Rosetta mission.

All teams have now completed their nominal science data deliveries from the comet phase, and samples of final data from the enhanced archiving activities went through a last science review in September 2019. The aim is to to complete any updates requested and deliver final products in the first half of 2020.

As soon as Rosetta’s operational mission ended, ESA established a number of activities with the Rosetta instrument teams to allow them to continue working on enhancing their archive content. The updates were focused on key aspects of an instrument’s calibration or the production of higher level data / information, and were therefore specific to each instrument. Most activities are now complete, but a few are still in the process of being closed in early 2020.

Almost all instrument teams have now provided a Science User Guide for their data, which have been highly appreciated by the scientists in the recent reviews. Many teams have also updated their calibrations to deliver higher level and/or derived products. For example, OSIRIS have delivered data with improved calibrations, as well as straylight corrected, I/F corrected, and three-dimensional georeferenced products. These are all already available in the archive. They now also provide their data additionally in FITS format, and have added quicklook (browse) versions of their products to allow an end-user to more easily identify the images they may be interested in. Internal straylight data and boresight corrected / full frame data are currently in preparation and will be added to the archive early this year.

Similarly, the VIRTIS team will update both their spectral and geometrical calibrations, and deliver mapping products to the final archive. The Rosetta Plasma Consortium instruments completed several cross-calibrations and a number of activities individual to each instrument, as well as producing illumination maps of the comet. The MIDAS team have produced a dust particle catalog from the comet coma. GIADA have produced dust environment maps with omni-directional products. COSIMA has delivered laboratory data to help understand their inflight measurements. An activity is also ongoing to produce data set(s) containing supporting ground-based observations of the comet.

The Rosetta ESA archiving team are also producing calibrated data for the NAVCAM instrument, and will include the latest shape models from the comet in the final Rosetta archive. Work is also underway to incorporate the radiation monitor (SREM) and spacecraft housekeeping (MUST) data into the archive.

This presentation will outline the current status of the Rosetta archive, and highlight the work being done this year to close out the archive and prepare it for legacy use.

How to cite: Heather, D., Fraga, D., O'Rourke, L., and Taylor, M.: The Rosetta Science Archive: Closing Out the Science Content, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5711, https://doi.org/10.5194/egusphere-egu2020-5711, 2020.

EGU2020-9308 | Displays | PS2.1

An Analysis of Regional H2O and CH3OH Production rates of Comet 67P from the MIRO Measurements

Hsuan-Ting Lai, Wing-Huen Ip, Wei-Ling Tseng, Ian-Lin Lai, and David Marshall

EGU2020-3347 | Displays | PS2.1

Determining the ion velocity in the inner magnetosphere of comet 67P/Churyumov–Gerasimenko using Rosetta IES measurements

Zoltan Nemeth, Karoly Szego, Aniko Timar, Lajos Foldy, Jim Burch, and Raymond Goldstein

Determining the ion bulk velocity is essential to understand the physics of the inner magnetosphere of comets. This velocity controls the strength of the ion-neutral drag force, which plays a very important role in the energy and momentum transfer processes of that region. Unfortunately there are no direct measurements of this quantity available. The energy thresholds of the ion instruments on board the Rosetta orbiter would prevent the direct detection of the bulk ion content of the plasma as long as the plasma is relatively slow and cold. The picture is further complicated by the spacecraft potential, which accelerates the thermal ions to energies higher than the measurement threshold, but effectively screens the magnitude and direction of their original velocity. That distortion effect is not arbitrary however; it is possible to recover the original ion velocity distribution from IES measurements by simulating the effects of the spacecraft potential on the ion motion. We performed these simulations for several bulk and thermal velocity as well as spacecraft potential values, and compared the results with IES measurements. From this we could determine the most probable values of the bulk and thermal speeds of the plasma ions in the inner magnetosphere of comet 67P/ Churyumov–Gerasimenko.

How to cite: Nemeth, Z., Szego, K., Timar, A., Foldy, L., Burch, J., and Goldstein, R.: Determining the ion velocity in the inner magnetosphere of comet 67P/Churyumov–Gerasimenko using Rosetta IES measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3347, https://doi.org/10.5194/egusphere-egu2020-3347, 2020.

EGU2020-13051 | Displays | PS2.1

Halogen-containing species at Comet 67P/Churyumov-Gerasimenko: Full mission results

Frederik Dhooghe, Johan De Keyser, Kathrin Altwegg, Nora Hänni, Martin Rubin, Jean-Jacques Berthelier, Gaël Cessateur, Michael Combi, Stephen Fuselier, Romain Maggiolo, and Peter Wurz

Dhooghe et al. (2017) studied halogen-bearing compounds in the coma of 67P/C-G with the Double Focusing Mass Spectrometer (DFMS) of Rosetta’s ROSINA instrument during a few time periods from first encounter up to perihelion (August 2014-August 2015). The main halogen-bearing compounds identified in the comet atmosphere were the hydrogen halides HF (hydrogen fluoride), HCl (hydrogen chloride) and HBr (hydrogen bromide). The halogen to oxygen ratios were found to vary between ~10-4 (Cl/O and F/O) to ~10-6 (Br/O), which shows these compounds have a very low abundance. In a follow-up article, De Keyser et al. (2017) observed an increase in the halogen-to-oxygen ratio as a function of distance, which suggests a distributed source for HF and HCl, probably through progressive release of these compounds from grains. Fayolle et al. 2017 and recent work by Altwegg et al. 2020 show that also CH3Cl and NH4Cl, respectively are present in the coma.

 

To further our knowledge on halogen containing species, we have applied recent improvements in DFMS data analysis techniques (De Keyser et al. 2019) to obtain a high quality time series for the complete mission duration. These data analysis techniques improve the retrieval of the abundances for overlapping mass peaks (18OH+ for F+, H218O+ for HF+, H34S+ for 35Cl+, and 36Ar+ and H234S+ for H35Cl+). The contribution of CS2++ to the signal of H37Cl+ has been determined from data for CS2+.

 

Based on the full mission data, and focusing on chlorine, we determine the 37Cl/35Cl isotopic ratio. An interesting finding is that the 35Cl+/H35Cl+ and 37Cl+/H37Cl+ ratios in the DFMS mass spectrometer do not match the NIST ones for the H35Cl and H37Cl parents. This indicates that at least one additional chlorine source must be present. The variability of halogen-containing species as a function of time is discussed, as well as the possible role of distributed sources.

 

Altwegg, K. et al. (2020): Evidence of ammonium salts in comet 67P as explanation for the nitrogen depletion in cometary comae. Nature Astronomy, in press

Dhooghe, F. et al (2017): Halogens as tracers of protosolar nebula material in comet 67P/Churyumov-Gerasimenko, MNRAS, 472, Issue 2, 1336, doi 10.1093/mnras/stx1911.

De Keyser, J. et al (2017): Evidence for distributed gas sources of hydrogen halides in the coma of comet 67P/Churyumov–Gerasimenko, MNRAS, 469, Issue Suppl_2, S695, doi 10.1093/mnras/stx2725.

De Keyser, J. et al. (2019): Position-dependent microchannel plate gain correction in Rosetta's ROSINA/DFMS mass spectrometer. IJMS, 446, 116232, doi 10.1016/j.ijms.2019.116232.

Fayolle et al. (2017): Protostellar and cometary detections of organohalogens. Nature Astronomy 1, 703, doi.org/10.1038/s41550-017-0237-7

How to cite: Dhooghe, F., De Keyser, J., Altwegg, K., Hänni, N., Rubin, M., Berthelier, J.-J., Cessateur, G., Combi, M., Fuselier, S., Maggiolo, R., and Wurz, P.: Halogen-containing species at Comet 67P/Churyumov-Gerasimenko: Full mission results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13051, https://doi.org/10.5194/egusphere-egu2020-13051, 2020.

EGU2020-19173 | Displays | PS2.1

Accurate reconstruction of comet 67P orbit through re-analysis of Rosetta ranging data acquired during proximity operations

Riccardo Lasagni Manghi, Marco Zannoni, Paolo Tortora, Michael Küppers, Laurence O'Rourke, Patrick Martin, Stefano Mottola, Uwe Keller, Frank Budnik, Matt Taylor, Laurent Jorda, Olivier Groussin, and Nicolas Thomas

Following its arrival at comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft successfully navigated in its proximity for two years, using a combination of Earth-based astrometric and radiometric tracking data as well as space-based optical navigation data. 

Depending on the mission phase, the orbital navigation system was tasked with the simultaneous estimation of both spacecraft and comet state, in addition to several other physical parameters including amongst others the comet rotational state, its gravitational field and the body-fixed coordinates of surface landmarks.

Estimating the heliocentric trajectory of 67P has proven to be challenging, due to the lack of reliable models to take into account the non-gravitational accelerations acting on the comet (particularly close to perihelion) and to occasional degradations of the ranging observables caused by geometrical constraints (solar conjunctions).

The accuracy of the resulting comet heliocentric trajectories, which show discontinuities in the order of tens of kilometers between consecutive short-arc solutions, was sufficient for spacecraft proximity operations, where navigators are mostly concerned by the relative comet/spacecraft position. However, a continuous and more accurate orbital solution is strictly coupled with the development of analytical models for non-gravitational accelerations and comet outgassing for which the Rosetta mission represents an ideal test case.

The work presented here represents a joint effort between academic institutions and ESA’s Flight Dynamics team to improve the accuracy of 67P’s orbit, by re-analyzing the radiometric data over long time scales for the whole duration of Rosetta proximity operations at comet 67P.

Details on the orbit determination process and filter implementation will be presented, together with a discussion on the achieved formal uncertainties and on the observables’ residuals.

How to cite: Lasagni Manghi, R., Zannoni, M., Tortora, P., Küppers, M., O'Rourke, L., Martin, P., Mottola, S., Keller, U., Budnik, F., Taylor, M., Jorda, L., Groussin, O., and Thomas, N.: Accurate reconstruction of comet 67P orbit through re-analysis of Rosetta ranging data acquired during proximity operations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19173, https://doi.org/10.5194/egusphere-egu2020-19173, 2020.

EGU2020-2476 | Displays | PS2.1

Nanoscale Dust Production at 1 Au; Identification and Tracking with 12 Spacecraft

Hairong Lai, Yingdong Jia, Martin Connors, and Christopher Russell

Interplanetary Field Enhancements are phenomena in the interplanetary magnetic field, first discovered near Venus, during an extremely long duration (12 hours) and large size (about 0.1 AU) passage across the Pioneer Venus spacecraft. Three and a half hours later and 21 x 106 km farther from the Sun, this structure, somewhat weaker and off to the side of the expected radial path of any solar initiated disturbance, was seen by first Venera 13 and then Venera 14, trailing behind V13. Since this discovery, many smaller such disturbances have been observed and attributed to collisions of small rocks in space at speeds of about 20 km/s at 1 AU and faster, closer to the Sun. All sightings with magnetometers and other space plasma instruments give very precise measurements of the radial structure (of usually the magnetic field), but the scale transverse to the solar radius is poorly defined, as is the temporal evolution of the structure from single spacecraft data.

On January 16, 2018, near Earth, 12 spacecraft equipped with plasma spectrometers and magnetometers observed the passage of a single Interplanetary Field Enhancement. The magnetic field profiles at the four 1 AU spacecraft were very similar. The profiles were obtained at different times appropriate to their locations. The 4 Cluster spacecraft were closer to the Earth and in a region in which the solar wind had slowed down because of the Earth’s bow wave (shock) in the solar wind. The disturbance in the shocked solar wind occurred at the time expected if the IFE structure had not been slowed by the plasma, but rather had proceeded with the momentum it had prior to the shock crossing. If the disturbance causing particles are small bits of rock (not protons), then they should have kept most of their momentum in crossing the bow shock. We view this as a complete test of the dust producing collisional origin of these Interplanetary Field Enhancements, and a clear demonstration of how the solar wind clears out the dust in the inner solar system produced by the continuing destructive collisional process.

How to cite: Lai, H., Jia, Y., Connors, M., and Russell, C.: Nanoscale Dust Production at 1 Au; Identification and Tracking with 12 Spacecraft, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2476, https://doi.org/10.5194/egusphere-egu2020-2476, 2020.

EGU2020-9599 | Displays | PS2.1

What can we learn from observations of small dust grains in the interstellar space?

Andrzej Czechowski and Ingrid Mann

A fraction of the dust that is contained in the local interstellar medium around the Sun can enter the heliosphere and be observed in the solar system. The exception is the small size component of the interstellar dust spectrum, which can be directly observed only beyond the heliopause. 

The charge-to-mass ratio of the interstellar dust grains of nanometer size can be high enough to make their dynamics highly sensitive to the magnetic field and plasma flow. Based on numerical simulations and analytical models, we show how the small interstellar grains entering the transition region between the undisturbed interstellar medium and the outer boundary of the heliosphere respond to plasma and magnetic field structures (in particular the heliospheric bow shock and the heliopause) expected in this region. We also point out which dust impact measurements from a spacecraft in the interstellar space would be most desirable for imaging the structure of the transition region by means of interstellar dust.

How to cite: Czechowski, A. and Mann, I.: What can we learn from observations of small dust grains in the interstellar space?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9599, https://doi.org/10.5194/egusphere-egu2020-9599, 2020.

EGU2020-7486 | Displays | PS2.1

Model Calculations of the F-Corona and inner Zodiacal Light

Saliha Eren and Ingrid Mann

The white-light Fraunhofer corona (F-corona) and inner Zodiacal light are generated by interplanetary (Zodiacal) dust particles that are located between Sun and observer. At visible wavelength the brightness comes from sunlight scattered at the dust particles. F-corona and inner Zodiacal light were recently observed from STEREO (Stenborg et al. 2018) and Parker Solar Probe (Howard et al. 2019) spacecraft which motivates our model calculations. We investigate the brightness by integration of scattered light along the line of sight of observations. We include a three-dimensional distribution of the Zodiacal dust that describes well the brightness of the Zodiacal light at larger elongations, a dust size distribution derived from observations at 1AU and assume Mie scattering at silicate particles to describe the scattered light over a large size distribution from 1 nm to 100 µm. From our simulations, we calculate the flattening index of the F-corona, which is the ratio of the minor axis to the major axis found for isophotes at different distances from the Sun, respectively elongations of the line of sight. Our results agree well with results from STEREO/SECCHI observational data where the flattening index varies from 0.45° and 0.65° at elongations between 5° and 24°. To compare with Parker Solar Probe observations, we investigate how the brightness changes when the observer moves closer to the Sun. This brightness change is influenced by the dust number density along the line of sight and by the changing scattering geometry.

-Stenborg G., Howard R. A., and Stauffer J. R., 2018: Characterization of the White-light Brightness of the F-corona between 5° and 24° Elongation, Astrophys. J. 862: 168 (21pp).

-Howard, R.A. and 25 co-authors, 2019: Near-Sun observations of an F-corona decrease and K-corona fine structure, Nature 576, 232–236.

How to cite: Eren, S. and Mann, I.: Model Calculations of the F-Corona and inner Zodiacal Light , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7486, https://doi.org/10.5194/egusphere-egu2020-7486, 2020.

EGU2020-18932 | Displays | PS2.1

A fragmentation model approach for low velocity impact charging

Tarjei Antonsen, Ingrid Mann, Jakub Vaverka, and Libor Nouzak

This work addresses the generation of charge during impacts of nano- to microscale projectiles on metal surfaces at speeds from 0.1 to 10 km/s. These speeds are well above the range of elastic deformation and well below speeds where volume ionization occures. Earlier models have utilized impurity diffusion through molten grains together with a Saha-equation to model impact ionization at these speeds. In this work we employ a model of capacitive contact charging in which we allow for projectile fragmentation upon impact. We show that this model well describes laboratory measurements of metal projectiles impacting metal targets. It also can describe in-situ measurements of dust in the Earth’s atmosphere made from rockets. We also address limitations of the currently most used model for impact ionization.

How to cite: Antonsen, T., Mann, I., Vaverka, J., and Nouzak, L.: A fragmentation model approach for low velocity impact charging, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18932, https://doi.org/10.5194/egusphere-egu2020-18932, 2020.

EGU2020-5268 | Displays | PS2.1

Gas flow through porous cometary media

Maria Schweighart, Günter Kargl, Patrick Tiefenbacher, and CoPhyLab Team

Over the last few decades, our picture of comets has been continuously changing and growing due to several successful space missions, as well as cometary simulation projects in the laboratory (e.g. KOSI 1987-1992, CoPhyLab 2018 - 2021). This work aims for a better understanding of the gas transport through a porous cometary surface layer. Therefore, gas flow measurements have been performed in our laboratory to investigate the permeability of several analogue materials, which have been chosen to mimic cometary surface properties.

For the first measurements, which we are reporting here, only dry materials, free of volatiles have been selected, to isolate the gas transport from gas production inside the materials. They include glass beads made of soda lime glass, which are sieved into separate fractions to obtain distinct grain size ranges from 45 µm up to 4.3 mm. The Mars simulant JSC-Mars 1 is used in the experiments, as well as JSC-1 as a lunar soil simulant. Furthermore, an Asteroid analogue material named UCF/DSI-CI-2 from the Exolith Lab in Florida is also used. A quartz sand called UK4 mined at a local quarry in Graz is investigated as well. In a further step, a sample is created by mixing different grain size fractions of the glass beads replicating the grain size distribution of the Asteroid simulant.

The materials are also treated on a shaking table in order to obtain the packing properties of the samples. For the gas flow experiments a cylindrical sample container, with 4 cm diameter, is filled with the sample (30 mm in height) and placed inside of the vacuum chamber at the interface of two separate volumes. Four pressure sensors covering different pressure ranges monitor the gas pressure in the two volumes. A vacuum pump in the lower volume removes the gas from the chamber and through a gas inlet a defined flow of the test gas (compressed air) is inserted into the upper volume. Due to this set-up, the gas flow can only pass through the sample material. To avoid particle fluidisation and thus a texture change in the sample the gas flow is intentionally directed downwards through the sample. The gas flow is controlled by regulators from 0.15 mg/s up to 19.2 mg/s. Via the measured pressure difference between the upper and lower volume, in equilibrium flow, the gas permeability and the Knudsen diffusion coefficient of the sample material are obtained. The gas flow experiments show that the grain size distribution and the packing density of the sample play a major role for the permeability of the sample. From the analysis of the permeability measurements it is clearly visible that the larger the grains the bigger the permeability. The measured permeability values range from 10-13 to 10-8 m². This work is part of the CoPhyLab project funded by the D-A-CH programme (DFG GU1620/3-1 and BL 298/26-1 / SNF 200021E 177964 / FWF I 3730-N36).

How to cite: Schweighart, M., Kargl, G., Tiefenbacher, P., and Team, C.: Gas flow through porous cometary media, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5268, https://doi.org/10.5194/egusphere-egu2020-5268, 2020.

EGU2020-12541 | Displays | PS2.1

Single-Crystal Structure Refinement of Presolar Silicon Carbide

Warren McKenzie and Przemyslaw Dera

Presolar silicon carbide, identified by anomalous 12C/13C, have long been the only direct physical sampling of asymptotic giant branch stars and Type-II supernovae (SNII) ejecta. The bulk of non-novae grains form in the dust clouds of 1-3M carbon stars in the thermally pulsing asymptotic giant branch (AGB) phase of their life. While these grains have been extensively studied for their unique isotopic signature characteristic of their exotic origin and trace gasses carrying the s-process and r-process nucleosynthetic signature, to date studies on their structures of presolar grains have been limited to electron diffraction surveys using transmission electron microscopy. We present high-resolution single-crystal structural refinement of presolar silicon carbides determined using data synchrotron x-ray diffraction data collected at Advanced Photon Source. Preservation and resolvability of the circumstellar pressure/temperature regime was determined with an examination of nanostrain states in several grains of presolar silicon carbide. By accounting for the environment present at (1) circumstellar formation, (2) interstellar transport, and (3) asteroidal and meteoritic storage and shock environments we hope to open a new opportunity to directly study the limits of our theoretical understanding of stellar structures.

How to cite: McKenzie, W. and Dera, P.: Single-Crystal Structure Refinement of Presolar Silicon Carbide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12541, https://doi.org/10.5194/egusphere-egu2020-12541, 2020.

EGU2020-3698 | Displays | PS2.1

Dust impact signals detected by Cassini RPWS instrument at Saturn

Libor Nouzak, Jiří Pavlů, Jakub Vaverka, Jana Šafránková, Zdeněk Němeček, David Píša, Mitchell Shen, Zoltan Sternovsky, and Shengyi Ye

Cassini spacecraft spent at Saturn almost half of the Saturn year. During these 13 years in the Saturn magnetosphere, the RPWS (Radio Plasma Wave Science) instrument recorded more than half a million of waveforms with signatures that can be interpreted as dust impact signals. The RPWS antennas in both dipole and monopole configurations operated with 10 kHz or 80 kHz sampling rates during the mission.
We qualitatively and quantitatively analyze the registered waveforms taking into account the spacecraft potential, density of the ambient plasma, magnitude of the Saturn’s magnetic field and its orientation with respect to the spacecraft. The magnetic field orientation is also used for distinguishing between signals resulting from dust impacts and signals produced by solitary waves, which can exhibit similar shapes. The results of analysis are compared with a prediction of the dust impact model that was recently developed on a base of laboratory simulations. The simulations used the reduced model of Cassini that was bombarded with submicron-sized iron grains in the velocity range of 1–40 km/s at the 3 MV dust accelerator operated at the LASP facility of University of Colorado. The model predicts generation of impact signals due to different fractions of collected and escaped electron and ion charges from the impact plasma plume and different timescales of their expansion. The core of the paper is devoted to a discussion of differences between model predictions and observations.

How to cite: Nouzak, L., Pavlů, J., Vaverka, J., Šafránková, J., Němeček, Z., Píša, D., Shen, M., Sternovsky, Z., and Ye, S.: Dust impact signals detected by Cassini RPWS instrument at Saturn, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3698, https://doi.org/10.5194/egusphere-egu2020-3698, 2020.

EGU2020-3095 | Displays | PS2.1

Components of Impact Plasma: Velocity and Temperature

Samuel Kočiščák, Åshild Fredriksen, Michael DeLuca, Jiří Pavlů, and Zoltan Sternovsky

Impact ionization is a process of plasma generation upon hypervelocity impact of a small body (e.g., interplanetary dust grain) onto a solid surface.  Such process may play an important role in astrochemistry. Understanding the plasma generation, we can clarify the interpretation of proclaimed dust impact detections onto antenna-equipped space experiments, which have become widely popular in the recent years.

We present the data gained in charge generation and collection experiments conducted at the University of Colorado IMPACT hypervelocity dust accelerator facility. The impacts are of sub-micrometer cosmic dust simulants onto a metal target in the range of velocities between 1 and 50 km/s. We discuss measured charge collection on a microsecond scale as well as aggregated results of electron and ion drift velocities and temperatures and specifically their dependence on the velocity of the impactor.

How to cite: Kočiščák, S., Fredriksen, Å., DeLuca, M., Pavlů, J., and Sternovsky, Z.: Components of Impact Plasma: Velocity and Temperature, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3095, https://doi.org/10.5194/egusphere-egu2020-3095, 2020.

EGU2020-3085 | Displays | PS2.1

Dust Interaction with Energetic Particles — A Laboratory Simulation

Jiří Pavlů, Libor Nouzák, Jan Wild, Jakub Vaverka, Ivana Richterova, Jana Šafránková, and Zdeněk Němeček

Dust grains in space frequently face energetic particles, e.g., ions, electrons, X-ray, positrons, etc. Such a broad variety of particle–dust interactions plays a significant role in dust charging and surface modification. The combination of high energy of particles together with a limited size of objects (dust) comprises interesting mesoscopic structure with non-obvious behavior. While in situ experiments are difficult and rare, we observed particular interactions experimentally in an electrodynamic trap. It allows us to study of a single dust grain temporal evolution under well defined conditions, i.e., to somewhat separate aforementioned processes and to investigate them individually. We present a summary of laboratory simulations and their
comparison with simple theoretical models. We discuss dust charging by different elementary particles and its importance for various space regions.

How to cite: Pavlů, J., Nouzák, L., Wild, J., Vaverka, J., Richterova, I., Šafránková, J., and Němeček, Z.: Dust Interaction with Energetic Particles — A Laboratory Simulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3085, https://doi.org/10.5194/egusphere-egu2020-3085, 2020.

EGU2020-3082 | Displays | PS2.1

Dust impact detections by a set of Faraday cups in the lunar environments

Oleksii Kononov, Jiří Pavlů, Libor Nouzák, Jana Šafránková, Zdeněk Němeček, and Lubomír Přech

The Bright Monitor of the Solar Wind (BMSW) for the Luna-Resurs-1 mission is an instrument designed for high-time (30 ms) resolution measurements of moments of the ion energy distribution by Faraday cups in the solar wind and in a plasma environment at altitudes between 65 and 150 km above the lunar surface. Previous studies performed by a similar instrument located on-board the Spektr-R spacecraft demonstrated a possibility to detect hypervelocity impacts of dust grains by such instruments Our analysis shows that the main problem of the reliable detection of dust impacts using such types of instruments is their sampling rate. In the paper, we present a novel design of a set of FCs that improves the ability of the dust detection using a simple identification algorithm that can store data with a higher sampling rate around the impact pulse. Moreover, we discuss a calibration of the detectors and their front-end electronics using the dust accelerator in order to find a relation between impact parameters and pulse heights.

How to cite: Kononov, O., Pavlů, J., Nouzák, L., Šafránková, J., Němeček, Z., and Přech, L.: Dust impact detections by a set of Faraday cups in the lunar environments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3082, https://doi.org/10.5194/egusphere-egu2020-3082, 2020.