Observations of Mercury's Plasma Sheet Horn: Characterization and Contribution to Proton Precipitation

Glass, A. N.; Raines, J. M.; Jia, Xianzhe; Sun, W.; Imber, Suzanne M.; Dewey, R. M.; Slavin, J. A.

doi:10.1029/2022ja030969

Cited by 7 publications

(5 citation statements)

References 66 publications

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“…Observations and simulations have revealed that magnetic reconnection on Mercury's dayside magnetopause enhances solar wind sputtering underneath the cusp (Fatemi et al., 2020; Poh et al., 2016; Raines et al., 2022), which cause enhancement of Na + ‐group ions at high latitudes (Sun, Slavin, et al., 2022). This sputtering effect is expected to also occur on the surface beneath the nightside plasma sheet (Glass et al., 2022).…”

Section: Discussionmentioning

confidence: 99%

MESSENGER Observations of Mercury's Planetary Ion Escape Rates and Their Dependence on True Anomaly Angle

Sun,

Dewey,

Jia

et al. 2024

Geophysical Research Letters

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This study investigates the escape of Mercury's sodium‐group ions (Na+‐group, including ions with m/q from 21 to 30 amu/e) and their dependence on true anomaly angle (TAA), that is, Mercury's orbital phase around the Sun, using measurements from MESSENGER. The measurements are categorized into solar wind, magnetosheath, and magnetosphere, and further divided into four TAA intervals. Na+‐group ions form escape plumes in the solar wind and magnetosheath, with higher fluxes along the solar wind's motional electric field. The total escape rates vary from 0.2 to 1 × 1025 atoms/s with the magnetosheath being the main escaping region. These rates exhibit a TAA dependence, peaking near the perihelion and similar during Mercury's remaining orbit. Despite Mercury's tenuous exosphere, Na+‐group ions escape rate is comparable to other inner planets. This can be attributed to several processes, including that Na+‐group ions may include several ion species, efficient photoionization frequency for elements within Na‐group, etc.

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Section: Discussionmentioning

confidence: 99%

MESSENGER Observations of Mercury's Planetary Ion Escape Rates and Their Dependence on True Anomaly Angle

Sun,

Dewey,

Jia

et al. 2024

Geophysical Research Letters

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“…For example, solar wind ion sputtering and micrometeroid impact vaporization compete in supplying Mercuryʼs exospheric high-energy particle population with refractory species (e.g., Ca and Mg), while photon-stimulated desorption dominates the supply of energetic volatile and moderately volatile species (i.e., Na, K, and S; Mangano et al 2007;Cassidy et al 2015;Schaible et al 2020;Grava et al 2021;Janches et al 2021). In the same way that fluxes, or precipitation rates, of the particles causing these processes are still in the process of being better constrained (i.e., proton precipitation for solar wind sputtering at Mercury's cusps in Fatemi et al 2020;Glass et al 2022;Raines et al 2022), the understanding of the underlying physics is still a work in progress. At the Moon, precipitation rates seem comparably trivial to compute, but the Moon traveling through Earth's magnetotail and localized crustal fields add complexity to the system (e.g., Lue et al 2011;Poppe et al 2018;Nénon & Poppe 2020).…”

Section: Space Weathering Of Exposed Rocky Surfacesmentioning

confidence: 99%

New Compound and Hybrid Binding Energy Sputter Model for Modeling Purposes in Agreement with Experimental Data

et al. 2023

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Rocky planets and moons experiencing solar wind sputtering are continuously supplying their enveloping exosphere with ejected neutral atoms. To understand the quantity and properties of the ejecta, well-established binary collision approximation Monte Carlo codes like TRIM with default settings are used predominantly. Improved models such as SDTrimSP have come forward, and together with new experimental data, the underlying assumptions have been challenged. We introduce a hybrid model, combining the previous surface binding approach with a new bulk binding model akin to Hofsäss & Stegmaier. In addition, we expand the model implementation by distinguishing between free and bound components sourced from mineral compounds such as oxides or sulfides. The use of oxides and sulfides also enables the correct setting of the mass densities of minerals, which was previously limited to the manual setting of individual atomic densities of elements. All of the energies and densities used are thereby based on tabulated data, so that only minimal user input and no fitting of parameters are required. We found unprecedented agreement between the newly implemented hybrid model and previously published sputter yields for incidence angles up to 45° from surface normal. Good agreement is found for the angular distribution of mass sputtered from enstatite MgSiO3 compared to the latest experimental data. Energy distributions recreate trends of experimental data of oxidized metals. Similar trends are to be expected from future mineral experimental data. The model thus serves its purpose of widespread applicability and ease of use for modelers of rocky body exospheres.

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“…In contrast to the Moon, Mercury's internal magnetic field causes a much more complicated interaction of the planet with the solar wind plasma (Slavin et al., 2008) and prevents impacts on large parts of the hermean dayside surface (Kallio & Janhunen, 2003; Sarantos et al., 2007; Winslow et al., 2014). Instead, precipitation is expected to be more localized on polar cusps at high day side latitudes (Raines et al., 2022), polar horns (Glass et al., 2022), or the night side (Benna et al., 2010). Precipitating ion fluxes are typically lower than the solar wind flux (Fatemi et al., 2020; Glass et al., 2022; Raines et al., 2022; Winslow et al., 2014) and ion energies are expected to vary between significantly smaller than the solar wind ion energy up to several keV (Fatemi et al., 2020; Glass et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

“…Instead, precipitation is expected to be more localized on polar cusps at high day side latitudes (Raines et al., 2022), polar horns (Glass et al., 2022), or the night side (Benna et al., 2010). Precipitating ion fluxes are typically lower than the solar wind flux (Fatemi et al., 2020; Glass et al., 2022; Raines et al., 2022; Winslow et al., 2014) and ion energies are expected to vary between significantly smaller than the solar wind ion energy up to several keV (Fatemi et al., 2020; Glass et al., 2022). Learning more about the surface of Mercury is thus strongly connected to establishing a full understanding of the plasma‐surface interaction to constrain precipitating fluxes of solar wind ions and magnetospheric species.…”

Section: Introductionmentioning

confidence: 99%

Energetic Neutral Atom (ENA) Emission Characteristics at the Moon and Mercury From 3D Regolith Simulations of Solar Wind Reflection

Szabo,

Poppe,

Mutzke

et al. 2023

JGR Planets

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The reflection of solar wind protons as energetic neutral atoms (ENAs) from the lunar surface has regularly been used to study the plasma‐surface interaction at the Moon. However, there still exists a fundamental lack of knowledge of the scattering process. ENA emission from the surface is expected to similarly occur at Mercury and will be studied by BepiColombo. Understanding this solar wind backscattering will allow studies of both Mercury’s plasma environment as well as properties of the hermean surface itself. Here, we expand on previous simulation studies of the solar‐wind‐regolith interaction with 3D grains in SDTrimSP‐3D to compare the predicted scattering energies and angles to ENA measurements from the Moon by the Chandrayaan‐1 and IBEX missions. The simulations reproduce a backward emission towards the Sun, which can be connected to the geometry of the regolith grain stacking. In contrast, the ENA energy distribution and its Maxwellian shape is mostly connected to the solar wind velocity. Our simulations also correctly describe a lunar ENA albedo between 10% and 20% and support its decrease with solar wind velocity. We further expand our studies to illustrate how BepiColombo will be able to observe ENAs at Mercury using hybrid simulations of Mercury’s magnetosphere as an input for the complex surface precipitation patterns. We demonstrate that the variable ion precipitation will directly influence ENA emission from the surface. The orbits of BepiColombo’s MPO and MMO/Mio spacecraft are shown to be suitable to observe ENA emission patterns both on a local and a global scale.

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Observations of Mercury's Plasma Sheet Horn: Characterization and Contribution to Proton Precipitation

Cited by 7 publications

References 66 publications

MESSENGER Observations of Mercury's Planetary Ion Escape Rates and Their Dependence on True Anomaly Angle

MESSENGER Observations of Mercury's Planetary Ion Escape Rates and Their Dependence on True Anomaly Angle

New Compound and Hybrid Binding Energy Sputter Model for Modeling Purposes in Agreement with Experimental Data

Energetic Neutral Atom (ENA) Emission Characteristics at the Moon and Mercury From 3D Regolith Simulations of Solar Wind Reflection

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