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The brightness ratio of H Lyman‐ α /H 2 bands in FUV auroral emissions: A diagnosis for the energy of precipitating electrons and associated magnetospheric acceleration processes applied to Saturn
Author(s) -
Tao Chihiro,
Lamy Laurent,
Prangé Renée
Publication year - 2014
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 - 10.1002/2014gl061329
Subject(s) - physics , electron precipitation , magnetosphere , electron , saturn , brightness , particle acceleration , atomic physics , range (aeronautics) , jupiter (rocket family) , plasma , flux (metallurgy) , astrophysics , astronomy , planet , nuclear physics , materials science , space shuttle , metallurgy , composite material
We propose that the ratio of the auroral brightness of H Lyman‐ α to that of far ultraviolet H 2 and the absolute value of the H 2 brightness provide good indicators of the acceleration versus nonacceleration processes for field‐aligned auroral electron precipitation in the Saturn magnetosphere‐ionosphere coupled system. This finding is based on model results indicating that this ratio is a decreasing function of the auroral electron energy over the whole auroral energy range, as previously suggested by Cassini observations. For electron energies above 5 keV, the results agree with the Knight relation, as in the environments of the Earth and Jupiter. On the other hand, decreasing electron flux with increasing electron energies below a few keV is also found and alternately explained as a nonacceleration reflecting the magnetospheric plasma distribution and/or wave‐particle interactions.