Publication Date:
2016-06-08
Description:
For most Cassini passes through the inner magnetosphere of Saturn, the hot-electron population (〉 few hundred eV) largely disappears inside of some cut-off L-shell. Anode-and-actuation-angle averages of hot-electron fluxes observed by the Cassini Electron Spectrometer (ELS) are binned into 0.1-R s bins in dipole L to explore the properties of this cutoff distance. The cut-off L-shell is quite variable from pass to pass (on time scales as short as 10-20 h). At energies of 5797 eV, 2054 eV, and 728 eV, 90% of the inner boundary values lie between L ~ 4.7 and 8.4, with a median near L = 6.2, consistent with the range of L values over which discrete interchange injections have been observed, thus strengthening the case that the interchange process is responsible for delivering the bulk of the hot electrons seen in the inner magnetosphere. The occurrence distribution of the inner boundary is more sharply peaked on the night side than at other local times. There is no apparent dependence of the depth of penetration on large-scale solar wind properties. It appears likely that internal processes (magnetic stress on mass-loaded flux tubes) are dominating the injection of hot electrons into the inner magnetosphere.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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