Abstract
Titan's nitrogen-rich atmosphere is directly bombarded by energetic ions, due to its lack of a significant intrinsic magnetic field. Singly charged energetic ions from Saturn's magnetosphere undergo charge-exchange collisions with neutral atoms in Titan's upper atmosphere, or exosphere, being transformed into energetic neutral atoms (ENAs). The ion and neutral camera, one of the three sensors that comprise the magnetosphere imaging instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images these ENAs like photons, and measures their fluxes and energies. These remote-sensing measurements, combined with the in situ measurements performed in the upper thermosphere and in the exosphere by the ion and neutral mass spectrometer instrument, provide a powerful diagnostic of Titan's exosphere and its interaction with the Kronian magnetosphere. These observations are analysed and some of the exospheric features they reveal are modelled.
Highlights
The exosphere is the uppermost part of an atmosphere, where collisions between particles are negligible (Chamberlain 1963)
charge energy mass spectrometer (CHEMS) provides the energetic ion (3–220 keV qK1) composition, low energy magnetospheric measurement system (LEMMS) measures the fluxes of the energetic ions and electrons and ion and neutral camera (INCA) measures the fluxes of energetic neutral atoms (ENAs) or ions, providing images with a 908!1208 field-of-view and with a good angular resolution
The resulting altitude profiles for these species are shown in figure 4. These altitude density profiles have been used to simulate the expected ENA fluxes, using as input for the parent ion fluxes those measured by magnetosphere imaging instrument (MIMI)/LEMMS in Saturn’s magnetosphere, in the vicinity of Titan, and the simulation results have subsequently been checked for consistency with the ENA data acquired by MIMI/INCA
Summary
The ion and neutral camera, one of the three sensors that comprise the magnetosphere imaging instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images these ENAs like photons, and measures their fluxes and energies. These remotesensing measurements, combined with the in situ measurements performed in the upper thermosphere and in the exosphere by the ion and neutral mass spectrometer instrument, provide a powerful diagnostic of Titan’s exosphere and its interaction with the Kronian magnetosphere. These observations are analysed and some of the exospheric features they reveal are modelled
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