Displays

There is a continuous flux of meteoroids entering the Earth's atmosphere, which are decelerated and heated by collisions with atmospheric molecules, and, depending on the meteoroid kinetic energy, they vaporize and form an ambipolar diffusing plasma trail, which is easily detectable using radar remote sensing. Specular meteor observations are a widely used radar technique to measure winds at the Mesosphere and Lower Thermosphere (MLT). The altitude dependent lifetime (decay time) of the meteor plasma columns provides valuable information about the mean temperature of the atmosphere.  Part of the success of these systems is based on the efficient scattering process compared to meteor head echoes.

Here we present observations with the Middle Atmosphere Alomar Radar System to detect the faintest observable meteors using the specular geometry, but a focused beam with a beamwidth of 3.6° and the full power of 866kW of the system. We compare our observations to an orbital dynamics model of JFC comets and derive a meteor velocity distribution for the observed population.

Further, we performed extensive modeling using a full-wave scattering model based on the model presented in Poulter and Baggaley, 1977. We conducted extensive simulations with the full-wave scattering model to investigate how different plasma distributions would affect the detectability of the meteoric plasma cylinders considering the initial trail radius, diffusion, and electron line density. The obtained reflection coefficients are validated with the triple frequency CMOR (Canadian Meteor Orbit Radar) measurements convolving them with the Fresnel integrals. Our results indicate that the plasma distribution can significantly alter the detectability. Further, the model shows that the observed decay time depends on the polarization of the transmitted wave relative to the meteor trajectory, which also revealed resonance effects for certain critical plasma frequencies. 

How to cite: Stober, G., Brown, P., Schult, C., Weryk, R., Campbell-Brown, M., and Pokorny, P.: Specular meteor observations and full wave scattering modelling: observing faint meteors , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9587, https://doi.org/10.5194/egusphere-egu2020-9587, 2020.

The impact of meteor showers and individual meteors on the ionosphere has been investigated during wintertime meteor showers using synchronised measurements of two DPS-4D Digisondes installed at Pruhonice (50°, 14.5°) and at Sopron (47.63°, 16.72°). Rather short distance between Pruhonice and Sopron allow us to perform special joint campaigns of vertical and oblique sounding under the high sampling rate to detect fine structures within ionospheric plasma.

High cadence campaigns have been performed to observe behavior of sporadic E layer (Es) during the Leonids, Geminids and Quadrantids meteor showers in 2018 and 2019. The time resolution of the ionograms have been set to approximately 0.5 - 2 ionograms per minute. We used vertical and oblique reflections to investigate the fine structure and the movement of Es layer. Based on the first results the oblique sounding is a good technique to detect the Es activity between two stations, however there were periods (typically 10 to 40 minutes of duration) when the Es was observed using oblique trace but there was no observation of Es layer in vertical ionograms. Furthermore, double Es structures have been detected more times for tens of minutes during the observation nights.

Beside the regular behavior of Es we concentrated on observation of intervals of increased plasma frequency in the Es region presumably directly induced by the meteors. In the framework of GINOP-2.3.2-15-2016-00003 (“Kozmikus hatások és kockázatok") an optical camera has been installed at the MTA Széchenyi István Geophysical Observatory (Sopron) in September 2019 with the cooperation of the Konkoly Observatory to monitor the meteors. Therefore, we were able to compare the ionograms measured during meteor showers with the optical data to determine the plasma trails of individual meteors. In the 20-25% of the observed meteors a faint Es layers were detected on the ionograms during and after (< 1 min) the optical record. The direction of the detected plasma traces determined by the SAO Explorer was in good agreement with the direction of the optically observed meteors in most of the cases. Consequently, the plasma trace of individual meteors could be detected on the high time resolution ionograms.

How to cite: Barta, V., Mosna, Z., Kouba, D., Igaz, A., and Sárneczky, K.: Impact of the Wintertime Meteor Showers on the Sporadic E Layer Activity at Midlatitudes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4775, https://doi.org/10.5194/egusphere-egu2020-4775, 2020.

Over the years, reports of meteor trails lasting up to one hour have periodically appeared in the literature. These observations are usually associated with particularly strong meteor showers, such as Leonids. In [Kelley et al. 2000] some interesting observations of such trails related to the 1998 Leonid meteor shower event are presented [2]. In publications devoted to the study of this phenomenon in the optical range, the main attention is paid to processes that cause a prolonged luminescence of meteor showers [Kelley et al., 2000]. Meanwhile, this phenomenon is of great interest for diagnosing the Earth upper atmosphere state and the ionosphere. The bulk of the work in this direction is based on radar observations of ionization traces, the duration of which in some cases reaches several minutes [Kashcheev et al., 1967].

This paper reports on long-lived meteor trails (LMT), which was recorded simultaneously using two optical instruments recording night sky emissions. The first all-sky camera is located at the Geophysical Observatory of the ISTP SB RAS, near the Tory (51.80 N, 103.10 E) and is designed to record the spatial picture of the 630 nm emission intensity [http: // atmos. iszf.irk.ru/ru/data/keo]. The second all-sky camera is located in the Sayan Solar Observatory of the ISTP SB RAS, near the Mondy (51.60 N, 100.90 E). A meteor trail lasting 35-40 minutes was recorded on November 18, 2017 after a meteoroid explosion on 22.23.19 UT with two cameras from different directions. Further, an algorithm was developed with the Python programming language the geographical coordinates of this event were calculated, as well as the height of the highlight

. The meteoroid explosion height and the ellipsoidal trail was being 65-70 km. Then the meteor track bow spread horizontally in a southward for 30-40 minutes at an average velocity of 58 m/s. This technique can be used to determine the main characteristics of various phenomena in the atmosphere, such as waves, SAR-arcs, meteor tracks and others.

This work was supported by a grant from the Russian Foundation for Basic Research N19-35-90093.

How to cite: Syrenova, T., Vasilyev, R., Beletsky, A., Mikhalev, A., and Maxim, E.: A technique for reconstructing the spatial characteristics of a long-lived meteor trails on all-sky cameras, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1168, https://doi.org/10.5194/egusphere-egu2020-1168, 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.

Irradiation of ices is a ubiquitous cause of chemical evolution of the surface of icy bodies of the solar system, due to solar UVs, solar wind particles, and magnetospheric particles. Sulfur is present in the solar wind and, in large quantities, in the jovian magnetosphere; in addition of acting as a projectile and inducing radiation chemistry, it is reactive and may be incorporated into the compounds produced. This may be a factor in increasing the chemical complexity of the surface of KBOs, TNOs, and jovian moons.

We have performed implantation of 105 keV sulfur ions into a water-methanol-ammonia ice at the Grand Accélérateur National d’Ions Lourds (GANIL) in Caen, France. Similar samples were also irradiated with argon (non-reactive projectiles). The samples were monitored in the infrared during the implantation process. The organic residues left after heating and sublimating the volatiles were then analyzed with Very High Resolution Mass Spectrometry (VHRMS). The infrared spectra of the argon-irradiated and sulfur-irradiated samples are qualitatively the same, but VHRMS shows the residue of the sulfur-irradiated sample contains more than a thousand of CHNOS formulas that are not present in the argon-irradiated sample. This indicates an active and rich sulfur chemistry induced by the implantation. The compounds formed are mostly aliphatic and can reach masses up to 700 amus. We discuss the implications for icy objects of the solar system and other ongoing experiments to explore the chemistry induced by sulfur implantation on the surface of the jovian moons.

How to cite: Bouquet, A., Ruf, A., Boduch, P., Schmitt-Kopplin, P., Vinogradoff, V., Duvernay, F., Giovanni Urso, R., Brunetto, R., Le Sergeant d'Hendecourt, L., Mousis, O., and Danger, G.: Formation of complex organosulfur compounds by sulfur implantation in astrophysical ice analogs – implications for the chemical evolution of the surface of icy objects, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8999, https://doi.org/10.5194/egusphere-egu2020-8999, 2020.

Previous investigations suggested local anomalies in Europa’s atmosphere, advancing the idea of possible water plumes. Now a global survey with the Keck observatory provided a direct detection (3.1 sigma) of line emission from H₂O at infrared wavelengths on one out of 17 observing dates in 2016 and 2017. The non-detections on the 16 other dates resulted in sensitive upper limits for H₂O abundance at various longitudes, providing reference to the rate and location of occurrence.

When active, outgassing at plumes locally increases the neutral density in Europa’s bound atmosphere. Such atmosphere anomalies in turn might lead to small scale (compared to Europa’s diameter) features in the electromagnetic interaction signals such as in magnetic field perturbations, or to an increased mass loss from Europa. The strength and detectability of plume-related magnetospheric signals depend on the relative abundance of plume gas (when active) compared to the sputtered atmosphere.

The new results from the infrared survey suggest that outgassing occurs at lower levels than previously estimated, with only rare localized events of somewhat stronger plume activity. In this presentation, we put these observations in context and discuss if and how plume activity might affect the magnetospheric environment.

How to cite: Roth, L., Paganini, L., Villanueva, G., Mandell, A., Hurford, T., Mumma, M., Retherford, K., and Blöcker, A.: A direct measurement of water vapor at Europa and implications for the magnetospheric environment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7593, https://doi.org/10.5194/egusphere-egu2020-7593, 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.

Ganymede is the largest moon of Jupiter and the only Solar System moon known to generate a permanent magnetic field. Motions of Jupiter’s magnetospheric plasma around Ganymede create an upstream magnetopause, where energy flows are thought to be driven by magnetic reconnection and/or Kelvin-Helmholtz Instability (KHI). Previous numerical simulations of Ganymede indicate evidence for transient reconnection events and KHI wave structures, but the natures of both processes remain poorly understood. Here we present an analytical model of steady-state conditions at Ganymede’s magnetopause, from which we conduct first assessments of reconnection and KHI onset criteria at the boundary. We find that reconnection may occur wherever Ganymede’s closed magnetic field encounters Jupiter’s ambient magnetic field, regardless of variations in magnetopause conditions. Unrestricted reconnection onset highlights possibilities for multiple X-lines or widespread transient reconnection at Ganymede. The reconnection rate is controlled by the ambient Jovian field orientation and hence driven by Jupiter’s rotation. We also determine Ganymede’s magnetopause conditions to be favorable for KHI wave growths in two confined regions each along a magnetopause flank, both of which grow in area whenever Ganymede moves toward Jupiter’s magnetospheric current sheet. KHI growth rates are calculated with the Finite Larmor Radius (FLR) effects incorporated and found to be asymmetric favoring the magnetopause flank closest to Jupiter. The significance of KHI wave growth on energy flows at Ganymede’s magnetopause remains to be investigated. Future progress on both topics is highly relevant for the upcoming JUpiter ICy moon Explorer (JUICE) mission.

How to cite: Kaweeyanun, N., Masters, A., and Jia, X.: Assessments of Magnetic Reconnection and Kelvin-Helmholtz Instability at Ganymede's Upstream Magnetopause, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2746, https://doi.org/10.5194/egusphere-egu2020-2746, 2020.

Phobos is the closest of the two moons of Mars and its surface is not only exposed to ions coming from the solar wind (mainly protons H+ and alpha particles He⁺⁺), but is also bombarded by ions coming from Mars itself (mainly atomic and molecular oxygen ions O⁺ and O₂⁺). Space weathering at Phobos would be intimately linked to the planetary atmospheric escape if Martian ions significantly alter the properties of the moon’s surface.
In this presentation, the long-term averaged ion environment seen by the surface of Phobos (omnidirectional and directional fluxes, and composition) is constructed from 4 years of ion measurements gathered in-situ by the NASA MAVEN mission. The MAVEN spacecraft repeatedly crossed the orbit of Phobos from January 2015 to February 2019 and was uniquely suited to unprecedently observe ions there with its three ion instruments: SWIA, STATIC, and SEP. These three experiments together constrain the entire range of ion kinetic energies that impact Phobos, from cold ions of a few eV to solar energetic ions of several MeV. In addition, the STATIC instrument (1 eV to 30 keV) is able to discriminate the mass of the observed ions by measuring their time-of-flight. This capability is important to understand the weathering of the surface of Phobos, as for instance the effect on the surface of a precipitating heavy molecular oxygen ion is significantly different from the one of a proton.
The relative importance of Martian and solar wind ions is in turn assessed from the observed ion omnidirectional fluxes for two space weathering effects: (1) surface sputtering, which is computed by using ion specie and energy-dependent sputtering yields available in the literature and (2) the production of vacancies inside the regolith grains, which is estimated with the SRIM software. (1) We find that Martian ions dominate solar wind ions in sputtering the surface of Phobos when the moon crosses the Martian magnetotail. We also reveal that molecular oxygen O₂⁺ ions sputter as much as or more from the surface of Phobos than atomic O⁺ ions. (2) Martian heavy ions significantly contribute to the production of vacancies in the uppermost nanometer of Phobos regolith grains. Finally, MAVEN directional flux measurements are used to study the anisotropy of the bombarding ion fluxes at Phobos, which we find implies an asymmetric weathering of the surface: the near side (always facing Mars) is primarily weathered by Martian ions, whereas the far side is primarily altered by solar wind ions. 

How to cite: Nenon, Q. and Poppe, A.: Ion weathering of the surface of the Martian moon Phobos as inferred from MAVEN ion observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2455, https://doi.org/10.5194/egusphere-egu2020-2455, 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.

We investigate the dynamics of solar wind - Moon interaction by means of large-scale Particle-in-Cell (PIC) simulations in this study. Implicit moment PIC method and open boundaries are implemented in the code (iPIC3D) allowing to use large-scale domains in three dimensions. Even though the Moon has no global dipolar magnetic field, satellite magnetic field measurements at low-altitude (8-80 km) orbits discovered the presence of patches of intense remanent magnetization of the lunar crust. In order to simulate the scattering effect of the lunar remanent magnetic field we implemented an empirical proton reflection model based on low-attitude survey by the Chandrayaan-1 spacecraft [Lue, 2011]. In this study we focus on the day side effects only and thus do not resolve wake and limb effects. Reflected ions are found to create an energized population of particles in the solar wind and are responsible for sub-ion scale instabilities over the strongest anomalies with non-Maxwellian ion distribution functions.

How to cite: Divin, A., Deca, J., Lue, C., and Beliaev, R.: Numerical simulation of ion reflection by lunar crustal magnetic fields, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18137, https://doi.org/10.5194/egusphere-egu2020-18137, 2020.

A fraction of up to 20% of the solar wind impinging onto the lunar surface is reflected as energetic neutral atoms back to space, as established by remote sensing, e.g. by the SARA instrument on Chandrayaan-1 or by IBEX. Mapping of these reflected energetic neutral atoms to the surface opened a new way to remotely study the solar wind precipitation onto the surface. However, the high reflection rate remained an enigma given the high porosity of the lunar regolith, but no measurements directly on the surface were available.

With the Advanced Small Analyzer for Neutrals (ASAN) mounted on the Yuyu-2 the rover of Chang'E-4, for the first time measurements of the energetic neutral atom flux originating from the lunar surface were preformed directly on the lunar surface itself. ASAN measures with a single angular pixel the energy spectrum of energetic neutral atoms reflected or sputtered form the surface with coarse mass resolution. ASAN uses the mobility of the rover to cover different solar wind illumination angles and scattering angles from the surface.

Since the landing of Chang'E-4 in the Von Kármán crater on the lunar far side in January 2019, ASAN has spent more than one year on the lunar surface and performed typically two measurement sessions per lunar day with nominal performance.

We review the ASAN instrument status and operations; present energy and mass spectra of energetic neutral atoms backscattered and sputtered from the surface, and discuss sputtering yields observed during different observation sessions. We put these observations into context of earlier remote sensing data by the SARA instrument on Chandrayaan-1.

How to cite: Wieser, M., Barabash, S., Wang, X.-D., Zhang, A., Wang, C., and Wang, W.: Solar wind interaction with the lunar surface: Observation of energetic neutral atoms on the lunar surface by the Advanced Small Analyzer for Neutrals (ASAN) instrument on the Yutu-2 rover of Chang'E-4. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9199, https://doi.org/10.5194/egusphere-egu2020-9199, 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.

Brightness asymmetries on the surface of Ganymede are thought to be caused by ion impact from Jovian co-rotating plasma. The Jovian Neutrals Analyzer instrument onboard the JUICE spacecraft will help investigate this theory by yielding a map of ion precipitation at the surface of Ganymede through the observation of low-energy Energetic Neutral Atoms (ENAs) (10 eV to 3300 eV) sputtered or backscattered by the Jovian plasma.

In order to optimize JNA operations planning at Ganymede, we estimate the expected energy distribution of ENAs caused by the impacting Jovian plasma. As an input, we use results from a three dimensional hybrid plasma simulation, which gives us the energy distribution of precipitating H+, O++ and S+++ at the surface of Ganymede. We then calculate the ENA yield using respectively Famà’s model (Famà, 2008) for the sputtering yield of water ice and Thompson-Sigmund’s model (Sigmund, 1969) for electronic sputtering to get the energy distribution of the ENAs.

How to cite: Pontoni, A., Shimoyama, M., Fatemi, S., Poppe, A., Futaana, Y., and Barabash, S.: Imaging of Ganymede through Energetic Neutral Atoms sputtered/backscattered from the surface, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19415, https://doi.org/10.5194/egusphere-egu2020-19415, 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.

Introduction

The flux of energetic ions (protons, oxygen and sulfur) near the Galilean moons were measured by the Energetic Particle Detector (EPD) on the Galileo mission (1995 - 2003). Near Galilean moons (such as Io and Europa) depletions of the energetic ion flux, of several orders of magnitude, were identified.

Such energetic ion depletions can be caused by the absorption of these particles onto the moon’s surfaces or by the loss due to charge exchange with neutral molecules in the atmospheres or potential plumes. To interpret the depletion features in the EPD data, a Monte Carlo particle tracing simulation has been conducted. The expected fluxes of the energetic ions are simulated under different scenarios including those with and without an atmosphere or plume. By comparing the simulated flux [YF1] to the EPD data, we investigate the cause of the depletion features with particular focuses on Europa and Io flybys.

Results

For Europa we report the following findings:

• For flyby E12 we find that a global atmosphere should produce a depletion region along the trajectory that is symmetrical to the closest approach, for energetic protons in the energy range of 80-220 keV. No such feature is visible in the data. Upper limits of the atmosphere are consistent with surface densities (⩽ 10⁸ cm^-3) and scale heights (50-350 km) of previous studies. We find that a depletion of energetic protons (80-220 keV) occurring before closest approach is consistent with the field perturbations associated with a plume. This plume features coincides in time with the plume reported by Jia et al., 2018.
• For flyby E26 we find that the depletions of energetic protons (80-220 keV) are consistent with a simulation that takes into account the perturbations of the fields as calculated by an MHD simulation and atmospheric charge exchange. Furthermore, a depletion feature occurring shortly after closest approach is consistent with the field perturbations associated with a plume, located near the plume reported by Arnold et al., 2019.
• From these investigations, we confirm, independently from previous reports, that the Galileo spacecraft could have passed near plumes.

For Io we report the following results:

• We identify regions of proton (80-220 keV) depletions during Io flybys I24, I27 and I31 extending beyond one Io radius. The depletions features are not consistent with Io as an inert body. We investigate atmospheric charge exchange as a cause for the depletions.

How to cite: Huybrighs, H., van Buchem, C., Blöcker, A., Roussos, E., Krupp, N., Dols, V., Yoshifumi, F., Barabash, S., Witasse, O., and Holmberg, M.: Energetic ion depletions near Europa and Io: the effect of plumes and atmospheric charge exchange, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4881, https://doi.org/10.5194/egusphere-egu2020-4881, 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 surfaces of icy bodies in the solar system are continuously irradiated by charged particles from planetary magnetospheres or from the solar wind. This irradiation induces chemical reactions in the surface ice and also acts as an atmospheric release process. Remote observations, theoretical modelling, and laboratory experiments must be combined to understand this plasma-ice interaction. In this presentation, we concentrate on laboratory experiments with electron irradiation (energy range of 0.1 to 10 keV) of water ice. The samples include thin ice films on a microbalance as well as thick layers of porous ice, resembling regolith. The physical and optical properties of the latter make them realistic analogues for the surfaces of icy moons.

We measure the sputtering yield and monitor the irradiation-induced alterations in the ice samples with a dedicated new time-of-flight mass spectrometer.
Previous results obtained with an earlier quadrupole mass spectrometer (Galli et al. 2018, Planetary and Space Sciences) indicated that most water escaping the ice sample upon electron irradiation does so in the form of the radiolysis products H₂ and O₂. The freshly produced H₂ appeared to leave the porous water ice sample immediately whereas the O₂ escape slowly increased until reaching a steady-state ratio of 1:2 of O₂ to H₂. With the new mass spectrometer, we investigate the release and storage of radiolysis products at a higher temporal resolution and sensitivity for a variety of ice sample porosities and thicknesses. We pay special attention to less abundant radiolysis products such as H₂O₂ and to the O₂/H₂O ratio in the irradiated water ice layer.

How to cite: Galli, A., Cerubini, R., Pommerol, A., Wurz, P., Vorburger, A., Rubin, M., Oza, A., Tulej, M., Thomas, N., and Ligterink, N. F. W.: Electron irradiation of water ice samples in the laboratory - Implications for icy moons and comets , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3420, https://doi.org/10.5194/egusphere-egu2020-3420, 2020.

In this study, optical video observations of meteors with the CAMS (Camera for All-sky Meteor Surveillance)-BeNeLux network and radio forward scatter observations with the BRAMS (Belgian RAdio Meteor Stations) network obtained on 4-5 October 2018  are combined in order to obtain an ionization profile along a meteor path.

The trajectory, initial speed and deceleration parameters of a given meteor are provided by the CAMS-BeNeLux data. For a given trajectory, the positions of the specular reflection points for radio waves are computed for each combination of a given BRAMS receiving station and the BRAMS transmitter. For each receiving station which recorded a meteor echo (depending on the geometry and the SNR ratio), the power profile is computed and the peak power values of the underdense meteor profiles are used to determine the ionization (electron line density) at the various specular reflection points along the meteor path. This is done using the McKinley (1961) formula which is strictly valid for underdense meteor echoes.  We discuss how we compute the gains of the antennas, the polarization factor, and how the peak power values are transformed from arbitrary units into watts using the signal recorded from a device called the BRAMS calibrator. We also discuss how to extend this study to overdense meteor echoes or those with intermediate electron line densities.

Finally, these results are combined with a simple ablation meteor model in order to obtain an estimate of the initial mass of the meteoroid.

Mc Kinley D.W.R., Meteor science and engineering, Mc Graw-Hill eds, 1961

How to cite: Lamy, H., Anciaux, M., Ranvier, S., Calegaro, A., and Johannink, C.: Ionization profile of meteors from simultaneous video and radio forward scatter observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5731, https://doi.org/10.5194/egusphere-egu2020-5731, 2020.

October 31st of 2015 the bolide lightened up the sky above Northern Poland. The main purpose of the project  was to define the place and time of its explosion in Earth’s atmosphere. To calculate these values and define the velocity of acoustic wave in the air, MATLAB model has been created. The model was based on seismic records of the event from GKP permanent seismological station and few stations of temporary array 13 BB star, arrival time of the wave to each station was read from seismograms. Using this data it was possible to indicate the narrowed area on plane where the explosion could take place. Next step was to model elevated point of explosion, time of the explosion, and the velocity of sonic wave in Earth’s atmosphere for spherical Earth 3D model, needed for the wave to travel from the point of explosion to seismological station.

How to cite: Ciechowska, H., Fronczak, A., Karasewicz, M., Mocek, K., Zawadzki, M., and Grad, M.: Pomeranian Bolide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5097, https://doi.org/10.5194/egusphere-egu2020-5097, 2020.

The increasing activities in space due to more and more countries with space programs, advancing commercialization, and large satellite constellation projects lead to a rising number of human-made objects in space. While many of those stay in orbit at high altitudes, objects in low Earth orbit reenter the atmosphere mostly disintegrating and injecting material into the atmosphere. The growing concern about space debris has led to policies encouraging deorbiting of satellites at the end of their lifetime. All that will increase the annual mass influx into the atmosphere by human-made (anthropogenic) objects in the future. We compare the influx of those objects to the natural mass influx of entering meteoroids of asteroidal, cometary, and planetary origin into Earth's atmosphere. We look at the mass and the elemental composition of the entering bodies also incorporating different ablation of those objects. This way, a quantitative assessment of the annual injection of aerosols and atomic remnants into the atmosphere is possible. Today, anthropogenic material makes up way less than 1 % of the overall injected mass. However, future large spacecraft constellations could increase the anthropogenic influx significantly, then contributing 4 % or more of the whole injection. As spacecraft have a high abundance of metal elements, the metal mass portion of the injection can reach up to 15 %. For some elements, the anthropogenic injection may even prevail the natural injection. This implies for future large satellite constellations that the anthropogenic injection can become significant with unknown effects on the upper atmosphere and the terrestrial habitat.

How to cite: Schulz, L. and Glassmeier, K.-H.: Concerning the impact of deorbiting spacecraft to the upper atmosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3931, https://doi.org/10.5194/egusphere-egu2020-3931, 2020.

Detection of charged dust in the spectrum of incoherent radars has previously been proposed and examined to some degree. These dust particles are of nanometer size and reside at mesospheric altitudes due to incoming ablating meteors. They are difficult to detect and thus their influence on atmospheric processes is hard to determine. Theoretical studies suggest that charged nanometer sized dust in the mesosphere can be successfully detected in the radar spectrum. However, current radar systems like EISCAT are not capable to distinguish adequately the dust signal from the main signal because the influence is small. We expect however, that the upcoming new EISCAT_3D radar will improve the observation conditions. We here present model calculations to examine the influence of the charged dust component on the radar signal, a so-called dusty plasma effect. Instead of the previously assumed one size dust component, we simulate the incoherent scatter spectrum including a large set of dust size bins. We show that different sizes, number density and charge of dust influence the signal in different ways, either causing a narrowing or broadening of the spectrum. Here the results are presented in a systematic way and specific conditions identified that provide the largest chance of dust detection in the signal. A simple charging model is used to model the most probable charge and altitude dependence to simulate realistic dust distributions that are then used as input to the radar spectrum model. These results can then be used to compare with actual radar measurements. Off which the new EISCAT_3D radar system, ready in 2022, might provide the adequate resolution for these requirements.

How to cite: Gunnarsdottir, T., Mann, I., and Miloch, W.: Model Calculations on the Influence of Charged Mesospheric dust on the Incoherent Radar Spectrum, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14165, https://doi.org/10.5194/egusphere-egu2020-14165, 2020.

The cosmic dust input into the Earth’s atmosphere has been estimated at 28 tonnes per day. However, the models behind this estimate do not include fragmentation. If the particles fragment significantly, the input rate of dust would be considerably higher. Millimetre sized meteoroids have been observed to fragment. If this is true for the majority of the cosmic dust particles that enter the Earth’s atmosphere (size range 10 micron to 1 mm), it would make a difference to the rates of ablation of these particles and our understanding of the meteoric inputs into the Earth’s mesosphere. Fragmentation would result in a broader size distribution and a greater number of 0.2 – 1.0 micron-sized particles sedimenting into the stratosphere.

The Meteoric Ablation Simulator (MASI) is a chamber for investigating the ablation of volatile species from meteoroid proxies. Here, we run it at relatively low temperatures to investigate the pyrolysis of hydrocarbon compounds. It has been proposed that organic carbon compounds act as a glue to hold the grains within micrometeoroids together. The carbon compounds are thought to be tarry, refractory kerogen compounds similar to those found in terrestrial oil shale. At moderate temperatures, these compounds pyrolyse into species such as butane and pentane.

The MASI employs a heated surface, the temperature of which can be varied from 300 to 1200 K. Once the surface is up to temperature, particles are dropped onto it. The ablating carbon-containing compounds are detected by mass spectrometry. The majority of the ablated carbon combusts to CO₂. Measuring the rate of CO₂ production as the particles are exposed to specific temperatures enables the temperature-dependent rate of pyrolysis of the carbon compounds to be measured.

To measure the effect of the removal of the carbon compounds on the strength of the particle, particles are subjected to yield stress tests in an atomic force microscope (AFM). Particles that have been flash heated, breaking bonds in the hydrocarbon glue, are expected to be more fragile.

Powdered meteorite samples (2% organic carbon) lose carbon over a broader range of temperatures than powdered oil shale (15% organic carbon). The effective activation energies measured for this pyrolysis are low – about 90 and 60 kJ mol^-1 for the oil shale and CM2 meteorite, respectively. This is likely a combination of 1) particles not reaching the surface temperature due to evaporative cooling and 2) the complexity of the reactions occurring in the carbonaceous particles as they heat. Analysis of TGA traces for oil shale samples give a higher effective activation energy of 191 kJ mol^-1. This value agrees with other TGA analyses of oil shale. In both cases, the biggest loss of carbon happens at around 700 – 800 K. AFM yield stress tests show evidence of fracturing, but so far only at pressures too high to be relevant for fragmentation in the atmosphere.

How to cite: Bones, D. L., Carrillo-Sánchez, J. D., James, A. D., Connell, S. D., Plane, J. M. C., and Mann, G. W.: Does organic carbon hold micrometeoroids together?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19548, https://doi.org/10.5194/egusphere-egu2020-19548, 2020.

The growth of particles is an important consideration toward a better understanding of the role of dust, ice and refractory particles in the upper mesosphere and lower thermosphere: in short, the MLT region (60 to 130 km). We investigate the conditions of dust growth via mutual collisions. It is assumed that meteoric smoke particles (MSP) are the main dust component in the mesosphere. MSP are small condensates that form in the diffusing meteor and are transported in the atmosphere where they grow by condensation. A second dust component are ice particles that form during summer months at mid and high latitude. These Polar Mesospheric Cloud (PMC) particles are composed of water ice and possibly include a fraction of the smaller MSP.

In this work, we investigate the effect of surface charge on the aggregation and growth of particles in the MLT region. The specific materials of the particles considered are similar to those typically found or expected in this region such as silica, metal oxides and ice, with particle sizes of 0.5 nm and larger. To consider the influence of the surface charges, we apply a model of the electrostatic interaction between particles of dielectric materials that, given the right conditions, includes the possibility for an attractive interaction between like-charged particles (Bichoutskaia et al. 2010). This like-charge attraction occurs due to the mutual polarisation of surface charge densities leading to regions of negative and positive surface densities close to the point of contact between the particles (Stace et al. 2011). This general model allows to investigate the interactions between particles of different size, charge and compositions. We simulate the interactions for particles of same charge and pairs of neutral and charged particles under different collision conditions in the MLT.

Bichoutskaia, E., (E. Besley), et al. J. Chem. Phys., 133(2), 024105 (2010).

Stace, A. J., et al. J. Colloid Interface Sci. 354(1), 417-420 (2011).

How to cite: Mann, I., Baptiste, J., Fox, J., Stace, A. J., and Besley, E.: The influence of surface charge on dust agglomeration growth in the mesosphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6717, https://doi.org/10.5194/egusphere-egu2020-6717, 2020.