Sputtering of sulfur by kiloelectronvolt ions: Application to the magnetospheric plasma interaction with Io |
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| Institution: | 1. Institute of Geosciences, Friedrich Schiller University Jena, Carl-Zeiss-Promenade 10, 07745 Jena, Germany;2. Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University, Albert-Einstein-Straße 15, 07745 Jena, Germany;3. Hawai’i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai’i at Manoa, Honolulu, HI 96822, USA;1. Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78238, USA;2. LATMOS/IPSL, CNRS, Paris, France;3. Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA;4. LASP, University of Colorado, PO Box 4384, 130 W. Main St., Frisco, CO 80443, USA;5. Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, USA;1. Department of Mechanical Engineering, Nanjing Tech University, Nanjing, Jiangsu, 210009 China;2. Department of Mechanical Engineering, Wuhan Institute of Technology, Wuhan, Hubei, 430070 China |
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| Abstract: | Measurements of total yields, temperature dependences, mass spectra, and energy spectra of molecules sputtered from condensed sulfur (S8) at low temperatures by keV ions are reported and results are given for Jovian plasma ion bombardment of Io. A change in the reflectance of the sulfur, which can be removed by annealing, is produced by the most penetrating ions and may be connected with the darker, colder polar regions on Io. The measured sputtering yields are much lower than those estimated earlier for room temperature sulfur films but are comparable to previous measurements of keV ion sputtering of SO2 at low temperatures. The corrected mass spectrum indicates that ≈66% of the total yield corresponds to S2 ejection while only 5 and 16% correspond to S and S3, respectively. Therefore, if ions reach the surface of Io its atmosphere will have a non-negligible sulfur component of primarily S2. The ejection of S and S2 is temperature independent for temperatures characteristic of most of the surface of Io. The energy spectrum for S has an approximate 1/E2 dependence at high ejection energies, whereas S2 and S3 fall off more rapidly. Assuming 50% coverage of both sulfur and SO2 and a thin atmosphere (e.g., nightside and polar region) the direct sputter injection of sulfur atoms and molecules into the Jovian plasma torus and the indirect injection due to coronal processes are estimated. These injection rates for sulfur are compared to those for SO2 showing that injection from sulfur deposits contributes 13% to the total mass injection rate of ∼2–3 × 1029 amu/sec. |
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