Multi-Fluid MHD Simulations of Europa’s Plasma Interaction: Effects of Variation in Europa’s Atmosphere
Harris, Camilla D. K.; Jia, Xianzhe; Slavin, James A.
2022-09
Citation
Harris, Camilla D. K.; Jia, Xianzhe; Slavin, James A. (2022). "Multi-Fluid MHD Simulations of Europa’s Plasma Interaction: Effects of Variation in Europa’s Atmosphere." Journal of Geophysical Research: Space Physics 127(9): n/a-n/a.
Abstract
Europa’s plasma interaction is inextricably coupled to its O2 atmosphere by the chemical processes that generate plasma from the atmosphere and the sputtering of magnetospheric plasma against Europa’s ice to generate O2. Observations of Europa’s atmosphere admit a range of possible densities and spatial distributions (Hall et al., 1998, https://doi.org/10.1086/305604). To better understand this system, we must characterize how different possible configurations of the atmosphere affect the 3D magnetic fields and bulk plasma properties near Europa. To accomplish this, we conducted a parameter study using a multi-fluid magnetohydrodynamic model for Europa’s plasma interaction (Harris et al., 2021, https://doi.org/10.1029/2020ja028888). We varied parameters of Europa’s atmosphere, as well as the conditions of Jupiter’s magnetosphere, over 18 simulations. As the scale height and density of Europa’s atmosphere increase, the extent and density of the ionosphere increase as well, generating strong magnetic fields that shield Europa’s surface from impinging plasma on the trailing hemisphere. We also calculate the precipitation rate of magnetospheric plasma onto Europa’s surface. As the O2 column density increased from (1–2.5) × 1014 cm−2, the precipitation rate decreased sharply then leveled off at 2 × 1024 ions/s for simulations with low magnetospheric plasma density and 6.4 × 1024 ions/s for simulations with high magnetospheric plasma density. These results indicate that the coupling between Europa’s plasma populations and its atmosphere leads to feedback that limits increases in the ionosphere density.Plain Language SummaryJupiter’s moon Europa is situated within Jupiter’s magnetosphere, where the flow of magnetospheric magnetic fields and plasma interacts with Europa’s atmosphere. We used a computational model for this interaction to study the effects of changes in Europa’s atmosphere on these magnetic fields and the flow of plasma, as well as on the precipitation of magnetospheric plasma to Europa’s icy surface. We performed 18 simulations, varying the density and spatial extent of the atmosphere and the density of the magnetospheric plasma flowing over Europa. We found that as the density of the atmosphere increased, the region of cold plasma around Europa called its ionosphere increased in density, and the plasma interaction caused more significant perturbations to the magnetic field. This shields the upstream-facing hemisphere of Europa’s icy surface, reducing the precipitation of magnetospheric plasma. This research is important because in the 2030s NASA’s Europa Clipper mission will make new observations of Europa, providing better constraints on the properties of Europa’s atmosphere and new observations of Europa’s plasma and magnetic fields. This study makes significant progress toward a more complete understanding of the coupling between Europa’s atmosphere and plasma interaction, in preparation for Europa Clipper.Key PointsA range of Europa’s possible atmospheric profiles were explored in magnetohydrodynamic simulations to quantify their impacts on the plasma interactionGrowth of Europa’s ionospheric density is self-limited by the coupling between Europa’s atmosphere and the surrounding plasma populationsProperties of Jupiter’s thermal plasma precipitating onto Europa’s surface vary strongly in response to Europa’s atmospheric conditionsPublisher
Wiley Periodicals, Inc. University of Arizona Press
ISSN
2169-9380 2169-9402
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