Multi‐Fluid MHD Simulations of Europa's Plasma Interaction Under Different Magnetospheric Conditions

• Published in: Journal of geophysical research. Space physics 2021-05, Vol.126 (5), p.n/a
• Main Authors: Harris, Camilla D. K., Jia, Xianzhe, Slavin, James A., Toth, Gabor, Huang, Zhenguang, Rubin, Martin
• Format: Article
• Language: English
• Subjects: Aerospace environments; Charge exchange; Charged particles; Computational fluid dynamics; Electron impact; Europa; Fluid flow; Flyby missions; Ionization; Ionosphere; Jovian magnetosphere; Jupiter; Jupiter atmosphere; Jupiter satellites; Lunar surface; Magnetic fields; Magnetohydrodynamics; Magnetospheric particles; Magnetospheric plasma; Mathematical models; Model accuracy; Moon; multi‐fluid MHD; Neutral particles; Parameters; Planetary magnetic fields; Planetary magnetospheres; Plasma; plasma interaction; Plasma interactions; Precipitation; Precipitation rate; Simulation; Sputtering; Three dimensional models
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2020JA028888

Europa hosts a periodically changing plasma interaction driven by the variations of Jupiter's magnetic field and magnetospheric plasma. We have developed a multi‐fluid magnetohydrodynamic (MHD) model for Europa to characterize the global configuration of the plasma interaction with the moon and its tenuous atmosphere. The model solves the multi‐fluid MHD equations for electrons and three ion fluids (Jupiter's magnetospheric O+, as well as O+ and O2+ originating from Europa's atmosphere) while incorporating sources and losses in the MHD equations due to electron impact and photo‐ionization, charge exchange, recombination and other relevant collisional effects. Using input parameters constrained by the Galileo magnetic field and plasma observations, we first demonstrate the accuracy of our model by simulating the Galileo E4 and E14 flybys, which took place under different upstream conditions and sampled different regions of Europa's interaction. Our model produces 3D magnetic field and plasma bulk parameters that agree with and provide context for the flyby observations. We next present the results of a parameter study of Europa's plasma interaction at three different excursions from Jupiter's central plasma sheet, for three different global magnetospheric states, comprising nine steady‐state simulations. By separately tracking multiple ion fluids, our MHD model allows us to quantify the access of the Jovian magnetospheric plasma to Europa's surface and determine how that access is affected by changing magnetospheric conditions. We find that the thermal magnetospheric O+ precipitation rate ranges from (1.8–26) × 1024 ions/s, and that the precipitation rate increases with the density of the ambient magnetospheric plasma. Plain Language Summary The moon Europa is embedded within Jupiter's magnetosphere, a region of space dominated by Jupiter's powerful magnetic field. The magnetosphere is filled with charged particles (plasma) which originate mainly from Jupiter's moon Io. Jupiter's magnetic field and plasma circulate throughout the magnetosphere. They flow around Europa and pile up as they approach Europa's ionosphere, a layer of plasma that surrounds the moon and partially shields the surface from the impact of Jupiter's magnetospheric plasma. Europa's ionosphere is generated from its atmosphere, which is in turn generated by surface sputtering, a process in which neutral particles are released when charged particles strike Europa's icy surface. We have deve