論文摘要

Generation of superthermal hydrogen beams in the vicinity of the Saturnian rings

[ Poster ]

Hua-Shan Shi (Institute of Space Science, National Central University, Taiwan); Wing-Huen Ip (Institute of Space Science, National Central University, Taiwan; Institute of Astronomy, National Central University, Taiwan); Meng-Tse Yang (Institute of Space Science, National Central University, Taiwan)

The Ion Neutral Mass Spectrometer (INMS), the Cassini Dust Analyzer (CDA) and the MIMI energetic charged particle experiments detected large fluxes of small nanodust grains during the ring plane crossing of the Cassini spacecraft in its Proximal mission. It has been further suggested by Mitchell et al. (Science, 362, 50, 2018) that the collisional interaction between the infalling dust grains and the hydrogen exosphere will lead to the production of a thin-disk population of high-speed H-atoms and H2-molecules in eccentric or escaping orbits. This scenario is interesting because such a process might be associated with the unexplained UVSI observation of a narrow hydrogen gas plume emitted from the near-surface region of Saturn (Shemansky, Liu and Merlin, Planet. Space Sci., 57, 1659, 2009). In this work, we will re-examine the orbital motion of ring dust particles of different masses by assuming a dust size frequency distribution. Using the dust mass influx values estimated by INMS and MIMI as constraints, the production rates of the putative high-speed hydrogen gas plume will be estimated from a set of Monte Carlo model calculations.