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.

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.

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.

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.

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.

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 B_Y of ~20 – 30 nT, followed by a gentle, but turbulent, return to background magnetic field values. The extrema in the B_Y component generally coincide with an extrema of opposite polarity in the B_X 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission was launched on 5 May 2018 and successfully landed at Elysium Planitia (4.5^oN, 135.9^oE)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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 B_Ycomponent 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 B_Ycomponent 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.

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.

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 2^nd 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 R_eff = 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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, CO₂ and 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.

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.

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.

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.

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.

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.

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.

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.

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.

Electric field data obtained by the Langmuir Probe and Waves (LPW) instrument on board the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft are used to identify signals related to dust impacts on the spacecraft body and/or on the instrument probes. The analyzed waveforms snapshots are 62.5 ms long (4,096 points sampled at 65,536 Hz). An automatic procedure to identify short electric field pulses with signatures corresponding to those expected for the dust impacts has been developed and applied to available data in years 2014–2018, resulting in about 40,000 of events. Each of the identified pulses is characterized by several quantitative parameters (polarity, magnitude, relaxation time, magnitude of a possible pre-spike). The event occurrence and respective quantitative parameters of detected pulses are then analyzed as a function of local plasma conditions in the Martian ionosphere (electron density and temperature), the spacecraft location, and the spacecraft potential. The obtained results are compared with a simple scheme of the signal formation upon a dust impact.

How to cite: Ševčíková, K., Němec, F., Nouzák, L., Vaverka, J., and Andersson, L.: Identification and preliminary analysis of dust impacts on the MAVEN spacecraft, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2438, https://doi.org/10.5194/egusphere-egu2020-2438, 2020.

Dust particles represent an important fraction of the matter composing the interplanetary medium. At 1 A.U. dust mass density is comparable to the one of the solar wind. The large number and broad diversity of dust particles detected by the radio instrument on the STEREO satellites recommend this mission for a closer dust investigation. In situ dust measurements are based on the detection of the charges generated by dust impacts, recorded by the S/WAVES instrument near 1 A.U. since the beginning of the STEREO mission. We study the electric signals produced by these impacts, using the waveform sampler data produced by the TDS subsystem of the radio instrument, connected to three monopole antennas. For this study, we concentrate on macroscopic dust particles (~0.1 microns) whose impact generated nearly simultaneous pulses on the antennas. In particular, we present statistics of typical shapes and features of these signals based on the TDS electric potential time-series and compare the data to a theoretical model of how pulses are generated by charge collection.
These results will have implications on dust detection from Parker Solar Probe and Solar Orbiter missions.

How to cite: Rackovic Babic, K., Issautier, K., and Zaslavsky, A.: In situ dust measurements in the solar wind from S/WAVES TDS instrument on STEREO mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8793, https://doi.org/10.5194/egusphere-egu2020-8793, 2020.

The risk of asteroids impacting the earth is a common space security issue facing human beings. Since the ground-based monitoring network cannot cover the space area comprehensively, there are cases of celestial body out of monitoring. In response to this problem, this report studies the space-based platform's monitoring system, and calculates its performance for orbit determination and monitoring of small celestial bodies. For small celestial bodies that are not in the catalog, the initial orbit determination needs to be performed before the orbit improvement. In addition, this paper proposes a method based on Fibonacci search method to quickly predict the impact location of asteroids.

How to cite: yezhi, S.: Space-based platform asteroid orbit determination and collision warning, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12597, https://doi.org/10.5194/egusphere-egu2020-12597, 2020.

Synthetic tracking technique uses multiple short exposure images to observe moving objects to prevent the objects from streaking in an individual frame. It integrates frames in post-processing, where the tracking of telescope at any desired rate can be simulated by shifting frames accordingly. Such an approach avoids trailing loss, thus improves detection sensitivity, especially for fast moving objects. It also yields accurate astrometry for moving objects independent of rate of motion with precision comparable to stellar astrometry. Using the Gaia DR2 catalog, we are able to demonstrate 10 mas level near-Earth-object (NEO) astrometry with the synthetic tracking technique. Accurate NEO astrometry allows us to determine NEO orbit more precisely. We discuss applications such as cataloging newly discovered NEOs with less measurements and/or from observation time windows covering shorter orbit arcs, better predicting the chance for a potentially hazardous asteroid to impact the Earth, measuring non-gravitational acceleration to infer physical properties of minor planets, and optical navigation for future spacecraft carrying optical communication lasers.

How to cite: Zhai, C., Shao, M., Saini, N., Trahan, R., Choi, P., Nazli, K., Evans, N., and Owen, W.: Accurate Near-Earth-Object Astrometry using Synthetic Tracking and Applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12729, https://doi.org/10.5194/egusphere-egu2020-12729, 2020.

In the past decades, the scintillations of Global Navigation Satellite System (GNSS) radio occultation (RO) measurements have been widely employed to study the occurrence of sporadic E (Es) layers. Recent results indicated that amplitude scintillation index (S4max) observations can be used to study the intensity of global Es layers. In this study, we show a statistical assessment of the hourly ionospheric Es layer measurements between 90 and 130 km from FORMOSAT-3/COSMIC satellites. The Es observations from FORMOSAT-3/COSMIC satellites are in agreement with those from ground-based ionosonde stations at different latitudes. With the successful launch of FORMOSAT-7/COSMIC-2, an accurate, high-resolution (< 5° ×5°×1 hour) map of Es layers on a global scale is available in the hopeful future.

How to cite: Yu, B., Scott, C., Xue, X., Yue, X., and Dou, X.: Derivation of metallic plasma layers in Earth's ionosphere (Sporadic E layer) from FORMOSAT-3/COSMIC satellites at a global scale, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2448, https://doi.org/10.5194/egusphere-egu2020-2448, 2020.

Meteoroids entering the Earth’s atmosphere produce ionized trails, which are detectable by radio sounding. Majority of such radar detections are the echoes from cylindrical ionized trails, which occur if the radar beam is perpendicular to the trail, i.e., the reflection is specular. Typically such echoes detected by VHF radars last less than one second. However, sometimes meteor radars (MR) observe unusually long-lived meteor echoes and these echoes are non-specular (LLNS echoes). The LLNS echoes last up to several tens of seconds and show highly variable amplitude of the radar return. The LLNS echoes are received from the non-field-aligned irregularities of ionization generated along trails of bright meteors and it is believed that key role in their generation belongs to the aerosol particles arising due to fragmentation and burning of large meteoroids. The occurrence and height distributions of LLNS are studied using MR observations at Sodankylä Geophysical Observatory (SGO, 67° 22' N, 26° 38' E, Finland) during 2008-2019. Two parameters are analyzed: the percentage and height distribution of LLNS echoes. These LLNS echoes constitute about 2% of all MR detections. However during certain meteor showers (Geminids, Perseids, Quadrantids, Arietids or/and Daytime ζ-Perseids, and Lyrids) the percentage of LLNS echoes is noticeably higher (about 6, 5, 4, 4, and 3%, respectively). Typically, the LLNSs occur ~2 km higher than other echoes (in June-July the height difference is reduced to ~1 km). Due to this elevation, a larger percentage of LLNSs is manifested as an upward shift of the height distribution of meteor trails during meteor showers. Moreover, during Lyrids, η-Aquariids, Perseids, Orionids, and Leonids the LLNS echoes occur noticeably, up to 3-6 km, higher than the echoes from other types of trails. Thus, enhanced heights of meteor detections during major meteor showers (Quadrantids, Lyrids, η-Aquariids, Arietids or/and Daytime ζ-Perseids, Perseids, Orionids, Leonids, and Geminids) are predominantly due to long-lived non-specular echoes from the non-field-aligned irregularities associated with large meteoroids.

How to cite: Kozlovsky, A., Lukianova, R., and Lester, M.: Occurrence and altitude of the non-specular long-lived meteor trails during meteor showers at high latitudes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1543, https://doi.org/10.5194/egusphere-egu2020-1543, 2020.

How to cite: Werner, A. L. E., Leblanc, F., Chaufray, J.-Y., and Modolo, R.: Monte Carlo test-particle model of Mercury's ionized exosphere: Global structure and dynamics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3149, https://doi.org/10.5194/egusphere-egu2020-3149, 2020.

We calculate the momentum and energy flux of ions measured by the Ion Composition Analyzer (ICA) on the Rosetta mission at comet 67P/Churyumov-Gerasimenko. We find that the total ion energy and momentum flux stay roughly constant over the mission, but the relative contribution of solar wind ions and cometary ions changes drastically depending on the spacecraft position in the ionosphere and distance from the comet to the sun. We also see that the magnetic pressure, calculated from the magnetic field measured by the Rosetta magnetometer, is on the order of the total ion momentum flux and roughly corresponds with the cometary ion momentum flux. Near both the beginning and end of the mission, solar wind momentum and energy flux are roughly two orders of magnitude larger than the corresponding heavy cometary ion fluxes. When the spacecraft enters the solar wind ion cavity near the comet’s periapsis, the solar wind energy and momentum flux drop drastically, mainly due to reduced density. Meanwhile, the cometary energy flux increases to be roughly equal to the solar wind flux earlier in the mission and the cometary momentum flux as measured by ICA becomes roughly an order of magnitude higher than previous and later solar wind fluxes. We also examine the changes in flux on two excursions, one on the dayside and one on the nightside of the comet, and see that during the nightside excursion, the cometary ion fluxes drop off roughly with the square of the distance from the comet. During the dayside excursion the flux was approximately constant, indicating that the excursion distance was small compared to the region where the observed ions were produced. ICA does not measure the lowest energy ions, so we also discuss the energy and momentum of the full ion population based on density estimates from the LAP and MIP instruments.

How to cite: Nilsson, H., Williamson, H., Stenberg Wieser, G., Richter, I., and Götz, C.: Energy and momentum flux around comet 67P throughout the Rosetta mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3061, https://doi.org/10.5194/egusphere-egu2020-3061, 2020.

In this presentation, we use data from THEMIS-ARTEMIS spacecraft and electromagnetic hybrid (kinetic ions, fluid electrons) simulations to describe the nature of the interaction between interplanetary shocks and the Moon. In the absence of a global magnetic field and an ionosphere at the Moon, solar wind interaction is controlled by (1) absorption of the core solar wind protons on the dayside; (2) access of supra-thermal and energetic ions in the solar wind to the lunar tail; (3) penetration and passage of the IMF through the lunar body. This results in a lunar tail populated by energetic ions and enhanced magnetic field in the central tail region. In general, ARTEMIS observations show a clear jump in the magnetic field strength associated with the passage of the interplanetary shock regardless of the position in the tail. Compared to the shock front observed in the solar wind, the magnetic field strength in the tail is stronger both upstream and downstream of the shock which is consistent with the expectations of larger field strengths in the tail. In addition, the transition from upstream to downstream magnetic field strength takes longer time as compared to the solar wind, indicating the broadening in space of the shock transition region. In contrast, plasma observations show that depending on the position of the spacecraft in the tail, a density enhancement in association with the shock front may or may not be observed. Using the observed solar wind conditions, we have used hybrid simulations to examine the interaction of interplanetary shocks with the Moon. The results indicate that by virtue of IMF passage through the lunar body, the magnetic field shock front also passes through the Moon and as such a jump in the magnetic field strength is observed throughout the lunar tail in association with the passage of the shock. As expected, the field strength in the upstream and downstream regions in the tail are larger than the corresponding values in the solar wind. In addition, the passage of the shock through the lunar tail is associated with the broadening of the shock front. The absorption of the core solar wind protons on the dayside introduces a density hole in the shock front as it passes through the Moon and the lunar tail and, as such, the shock front as a whole is disrupted. This hole is gradually filled with the ambient plasma while it travels further down the tail until eventually the shock front is fully restored a few lunar radii away from the Moon. The simulation results are found to be consistent with ARTEMIS observations. Here we also discuss the impacts of shock Mach number on the interaction. These results depict the lunar environment under transient solar wind conditions, which provide helpful information for the NASA’s plan to return humans to the Moon.

How to cite: Zhou, X. and Omidi, N.: Interaction of Interplanetary Shocks with the Moon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5971, https://doi.org/10.5194/egusphere-egu2020-5971, 2020.

The Reiner Gamma swirl is one of the most prominent albedo features on the lunar surface. Its modest spatial scales and structure allows fully kinetic modelling. The region therefore presents a prime location to investigate the lunar albedo patterns and their co-location with magnetic anomalies. The precise relationship between the impinging plasma and the swirl, and in particular, how these interactions vary over the course of a lunar day, remains an open issue.

Here we use the fully kinetic particle-in-cell code,  iPIC3D, coupled with a magnetic field model based on Kaguya and Lunar Prospector observations, and simulate the interaction with the Reiner Gamma anomaly for all plasma regimes the region is exposed to along a typical orbit, including different solar wind incidence angles and the Moon's crossing through the terrestrial magnetosphere. We focus on the impact of the solar wind alpha population and construct energy and velocity distributions in key locations surrounding the interaction region of the anomaly.

The energy flux profile provides a better match to the albedo pattern only when integrating over the full lunar orbit. Including He²⁺ as a self-consistent plasma species improves the brightness ratios between the inner and outer bright lobes, the dark lanes, and the mare background. However, substantial differences between the observed albedo pattern and the predicted flux remain.  For example, the bright outer lobes are substantially brighter than predicted and the central portion of the anomaly is darker than predicted. This is likely due to an incomplete model of the near-surface field structure.

Solar wind standoff can explain the large-scale correlation between the Reiner Gamma swirl and the co-located magnetic anomaly. In particular, the outer bright lobes emerge in the simulated weathering pattern only when integrating over the entire lunar orbit, although they are much weaker than observed. Both the proton and helium energy flux to the surface need to be taken into account to best reproduce the swirl pattern. A complete understanding of the solar wind interaction with lunar magnetic anomalies and swirl formation could be vastly improved by low altitude measurements of the magnetic field and solar wind.

How to cite: Deca, J., Hemingway, D. J., Divin, A., Lue, C., Poppe, A. R., Garrick-Bethell, I., Lembège, B., and Horányi, M.: Simulating the Reiner Gamma Swirl and Magnetic Anomaly: The Impact of the Solar Wind Alpha Population, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6186, https://doi.org/10.5194/egusphere-egu2020-6186, 2020.

Under nominal solar wind conditions, a low density wake region forms downstream of the nightside lunar surface.  However, the lunar plasma environment undergoes a transformation as the Moon passes through the Earth’s magnetotail, with the warm plasma typically not having a strong flow, and thus the wake structure disappears.  However, while in the tail, there can be a sudden intense change due to solar-driven events such as coronal mass ejections.  With a new planned human presence on the Moon, it is important to understand the near-surface plasma environment’s response to these extreme conditions.  We investigate the response of the lunar wake to a passing coronal mass ejection on 2012 March 8 while crossing the Earth’s magnetotail using both a large-scale MHD model of the Earth’s global magnetosphere and smaller-scale 3-D hybrid-PIC simulations.

The CME plasma shock was detected by the Wind spacecraft around 10:30 UT and in the Earth’s magnetotail around 11:20 UT by the ARTEMIS spacecraft in lunar orbit.  Wind observations are used as time-dependent up-stream conditions for a 24-hour global magnetosphere MHD simulation run through NASA’s Community Coordinated Modeling Center using the OpenGGCM model.  Extracted plasma parameters from the ARTEMIS spacecraft following the plasma shock are used as upstream static boundary conditions for hybrid-PIC simulations using the AMITIS code.

Results for the hybrid-PIC lunar wake simulations performed during a momentary jump in magnetotail plasma velocity and density show a short misaligned plasma void relative to nominal SW conditions.  MHD results indicate that changes near the Moon appear as a result of a warped magnetopause boundary moving inward after 11:00 UT, causing the Moon to enter the magnetosheath.  These results also show a number of plasmoids developing and propagating down the tail, including one seen at 11:20 UT that corresponds temporarily with plasmoid-like features in the ARTEMIS magnetic field profiles.

How to cite: Rasca, A., Fatemi, S., Farrell, W., Poppe, A., and Zheng, Y.: A Double-Disturbed Lunar Plasma Wake, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9656, https://doi.org/10.5194/egusphere-egu2020-9656, 2020.

A number of moon-sized objects in the solar system are characterized by the formation of a surface-bound exosphere. These include the Moon, Ceres, Jupiter’s icy moons, namely, Europa, Ganymede and Callisto, and several of the Saturnian icy moons including Rhea, Dione, and Tethys. There are several major source mechanisms ranging from micrometeoroid bombardment, photo-stimulated desorption, and energetic ion sputtering - in addition to the surface (or subsurface) thermal sublimation in the case of Ceres and the icy Moon. It is interesting that Ceres and the Moon could experience extreme space weather effects when they encounter large solar flare events or coronal mass ejection events. An important consequence is the production of a transient exosphere due to the sudden increase of ion sputtering rates. We have developed time-dependent Monte Carlo models that can be applied to the Moon and Ceres. Some simulation results will be described in this presentation with a view to construct the CME-driven H₂O and O₂ exosphere of Ceres and the flare-up of the lunar sodium corona and tail emission.

How to cite: Shi, H.-S., Chen, Z.-X., and Ip, W.-H.: On the Space Weather Effect and CME-Driven Exospheres of the Moon and Ceres, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13261, https://doi.org/10.5194/egusphere-egu2020-13261, 2020.

Io and Europa are embedded in Jupiter’s magnetosphere and the moons’ surfaces and atmospheres interact with the surrounding moving magnetized plasma forming a complex plasma interaction. The interaction scenarios for both moons are characterized by inhomogeneities in the atmospheres from local outgassing. These inhomogeneities affect the electromagnetic environment but can also lead to localized features in the moons' auroral emissions. The moons’ aurora in turn is sensitive to the energy or temperature of the exciting electrons in the plasma. To simulate the interaction scenarios including atmospheric inhomogeneities and aurora generation, we expand the magnetohydrodynamic code MPI-AMRVAC by implementing a self-consistent description of the electron temperature and the electron density where the cooling by inelastic collisions between the magnetospheric electrons and the atmosphere, and the electron heat flux from the magnetospheric plasma to the moons’ ionosphere are included. Furthermore, the numerical schemes of MPI-AMRVAC are able to handle discontinuities that arise from the atmospheric inhomogeneities. Here, we demonstrate the implementation of the physical effects and first modeling results of Io’s and Europa’s plasma interaction with the advanced MHD code.

How to cite: Blöcker, A., Roth, L., Ivchenko, N., Chané, E., and Keppens, R.: A new MHD model for Io's and Europa's plasma interaction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21771, https://doi.org/10.5194/egusphere-egu2020-21771, 2020.

The electromagnetic interaction between Jupiter and its innermost Galilean moon Io is a prime example for moon-planet and star-planet interaction. A very striking feature is the Io Foot Print (IFP) in Jupiter’s upper atmosphere. With the Juno spacecraft orbiting Jupiter, new insights about the complex structure of the IFP have been achieved which can not be fully explained by existing models. A deeper understanding is necessary to explain these Juno observations [Mura et al. 2018, Szalay et al. 2018]. For that purpose a simulation of the system with the single fluid MHD-Code Pluto is set up to study the Alfvén wing generated by Io in detail. In our study, we use a model similar to Jacobsen et al. 2007 with a constant magnetic field and spatially varying density. Then we increase the complexity of this model by including a more realistic wave generator, i.e. Io, and a more complex model of the Jovian inner magnetosphere.

How to cite: Schlegel, S. and Saur, J.: Io’s auroral footprints: MHD simulations of the interaction between Io and Jupiter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19091, https://doi.org/10.5194/egusphere-egu2020-19091, 2020.

The water vapour vertical distribution is an eloquent gauge of the relative roles of the various sources, sinks and processes that control the Martian water cycle. However, its behaviour is still poorly studied while it is instrument for our understanding of the loss of water from Mars to space, which results from the transport of water to the upper atmosphere where it is disassociated to hydrogen atoms that later escape. We use the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter to characterize the water distribution with altitude. Here we present results of the Atmospheric Chemistry Suite (ACS) instrument NIR channel for the first year of TGO observations covering the almost full year from Ls 160° of the Martian year 34 (April 2018) to Ls 130° of the Martian year 35 (January 2020). Simultaneous measurements of the water vapour mixing ratio, temperature and dust vertical distribution and formation of water ice clouds allow us to constrain the complex water behaviour and estimate the saturation state of H2O. Water profiles during the 2018-2019 southern spring and summer stormy seasons show that high altitude water is preferentially supplied close to perihelion and that large supersaturation occurs even when clouds are present. Here we attempt to complete the story by studying water vapor during the northern spring and summer to explore whether saturation impacts water transport between hemispheres in this season. The data analysis of MY35 was supported by RSF (project No. 20-42-09035).

How to cite: Fedorova, A., Montmessin, F., Korablev, O., Luginin, M., Trokhimovskiy, A., Belyaev, D., Alday, J., Ignatiev, N., Lefevre, F., Olsen, K., Millour, E., Bertaux, J.-L., Shakun, A., Grigoriev, A., Patrakeev, A., Korsa, S., Wilson, C., Forget, F., and Maattanen, A.: The distribution and saturation of water vapor as inferred from ACS during the first Martian year of TGO Science observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17962, https://doi.org/10.5194/egusphere-egu2020-17962, 2020.

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging NASA’s spacecraft, known as MESSENGER, flew by Mercury on September 29, 2009. It was the spacecraft’s third and final flyby, before it went into orbit around the planet. The flyby presented a unique trajectory approach and perspective on the planet’s exosphere, not available when in orbit. We present very high spectral resolution ground-based data obtained at the University of Texas McDonald 2.7-m telescope. These data were acquired within hours of the data taken with the Ultraviolet and Visible Spectrometer (UVVS) onboard MESSENGER. Both datasets targeted similar spatial regions, in the polar altitudes of Mercury. We compare the sodium emissions from both measurements in the exosphere. We find that close to the surface, both intensity measurements match, but the intensities fall off differently with altitude, with the MESSENGER data showing an exponential drop off, sharper than that of the ground-based data; an effect that we attribute to atmospheric seeing. In addition, our ground-based data provided Full Width Half Maximum (fwhm) speeds and Doppler shift speeds; our results suggest energetic processes took place in the polar regions on the dusk side of the planet, but arguably on the dawn side as well. We confirm previous conclusions of Leblanc et al. (2008, 2009) where signatures of energetic processes seem to be coupled with high fwhm speeds and intensity peaks. We compare our Doppler shift velocities with previous works, and find agreement within the uncertainties with Potter et al., (2013) on their transit velocity measurements. Although our peak emissions along the terminator vary in structure and in brightness, they do not exhibit distinctive signatures in the intensity profiles at altitudes above the poles, when compared with convolved MESSENGER space data.

How to cite: Mouawad, N., Chebly, J., Leblanc, F., Fraine, J., and Fatima, K.: Mercury's Na exosphere as seen with very high spectral resolution from the ground, and from space with MESSENGER, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22650, https://doi.org/10.5194/egusphere-egu2020-22650, 2020.