PS2.2

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

         
References :

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

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

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

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

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

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

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

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

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

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

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