Magnetospheric plasma sputtering of Io's atmosphere |
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| Institution: | 1. Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA;2. Goddard Planetary Heliophysics Institute, University of Maryland Baltimore County, 21228, USA;3. Southwest Research Institute, San Antonio, TX 78228, USA;4. University of California, Los Angeles, CA 90095, USA;5. Jet Propulsion Laboratory, Pasadena, CA 91109, USA;6. Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA;1. Horticultural Crops Research Unit, USDA ARS, 3420 NW Orchard Avenue, Corvallis, OR, 97330, USA;2. Department of Horticulture, Oregon State University, Corvallis, OR, 97330, USA;1. National Institute of Materials Physics, 077125 Magurele, Romania;2. National Research and Development Institute for Cryogenics and Isotopic Technologies – ICSI, 240050 Ramnicu Valcea, Romania;3. Faculty of Power Engineering, Politehnica University of Bucharest, 060042 Bucharest, Romania;1. Indian Institute of Geomagnetism, New Panvel, Mumbai, India;2. Department of Physics, University of Bahrain, Bahrain |
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| Abstract: | The existence of an atmosphere at Io is presumed and used as a starting point to generate neutral coronae produced by magnetospheric ion sputtering from the exobase and to calculate injection of neutrals and ions into the plasma torus. Several different exobase heights, temperatures, and compositions are used to characterize the neutral and ion ejection processes associated with possible atmospheres. Collision ejection from the sputter-produced corona is shown to be an important supply of neutrals for all atmospheres considered. The net injection rates are compared with estimates of the rates required to populate the plasma torus. We show that by including the sputtered atmospheric corona produced by assuming an unattenuated incident ion flux, the supply rate to the torus can be satisfied with an exobase very close to the surface. An exobase close to the surface would imply that the atmosphere at Io is not robust enough to support a fully photodissociated corona and that a significant fraction of the incident plasma ions can penetrate to the surface, providing a sputter source of atmospheric gas. Conversely, a high exobase could only be consistent with the estimated supply rates if the incident plasma flux is attenuated or deflected. The results presented scale approximately with the magnitude of the incident ion flux and, therefore, can be used as knowledge of both the plasma flow and atmospheric composition improve. |
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