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Surface-plasma Interactions at Europa in Draped Magnetospheric Fields: the Contribution of Energetic Electrons to Energy Deposition and Sputtering

Presentation #501.04D in the session Icy Galilean Satellites: Magnetosphere and Exosphere (Oral Presentation)

Published onOct 23, 2023
Surface-plasma Interactions at Europa in Draped Magnetospheric Fields: the Contribution of Energetic Electrons to Energy Deposition and Sputtering

We calculate the time-varying spatial distribution of energetic magnetospheric electron influx onto Europa’s surface by combining a hybrid model of the moon’s draped electromagnetic environment with a relativistic particle tracer. We generate maps of the energetic electron influx patterns at four distinct locations of Europa relative to the center of the Jovian magnetospheric current sheet. For a full synodic rotation of Jupiter, these results are applied to constrain the averaged number and energy influx patterns as well as the O2 sputtering rates associated with energetic electron precipitation. We also determine the relative contributions of magnetospheric ions and electrons to surface erosion and exospheric genesis at Europa. Our major results are: (a) Except for a small region near Europa’s downstream apex, the moon’s entire surface is exposed to heavy irradiation by magnetospheric electrons. (b) The spatial distribution of energetic electron influx onto Europa’s surface is only slightly modified by field line draping and the induced magnetic field from the moon’s subsurface ocean. (c) Magnetospheric electrons contribute only 28% of the total power deposited onto Europa’s surface by charged particle impacts; the other 72% is imparted by ions. (d) Of the O2 released from Europa’s surface via charged particle sputtering, electrons contribute roughly 20%, while the other 80% stems from magnetospheric ions. (e) The spatial distribution of electron energy influx and the observed concentrations of sulfuric acid (H2SO4) are only weakly correlated, suggesting that energy deposition by magnetospheric electron impacts is not a necessary agent for H2SO4 production within Europa’s surface.

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