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Saturn's Innermost Radiation Belt Throughout and Inward of the D‐Ring
Author(s) -
Kollmann P.,
Roussos E.,
Kotova A.,
Regoli L.,
Mitchell D. G.,
Carbary J.,
Clark G.,
Krupp N.,
Paranicas C.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl077954
Subject(s) - enceladus , saturn , physics , van allen radiation belt , rings of saturn , atmosphere (unit) , radiation , albedo (alchemy) , proton , magnetosphere of saturn , magnetosphere , astronomy , nuclear physics , meteorology , planet , magnetopause , art , plasma , performance art , art history
Cassini discovered Saturn's innermost radiation belt during the end of its mission. The belt is populated with relativistic protons, probably up to the trapping limit of ≈20 GeV. It extends from Saturn's dense atmosphere into and throughout the D‐ring. The A–C rings separate this belt entirely from the previously known radiation belts, suggesting that the innermost radiation belt is populated entirely via cosmic ray albedo neutron decay. We find that the proton pitch angle distributions are consistent with being shaped by losses to the D‐ring and the upper atmosphere rather than, for example, wave‐particle interactions. This supports that the main loss process of this new radiation belt is energy loss in neutral material, different from Saturn's other radiation belts. This property constrains the overall scale height of Saturn's exosphere to <700 km and the average D‐ring water molecule column density to being about 1 order of magnitude below the Enceladus gas torus.