Open AccessOn the origin of Saturn's outer auroral emission
Author(s) -
Grodent Denis,
Radioti Aikaterini,
Bonfond Bertrand,
Gérard JeanClaude
Publication year - 2010
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009ja014901
Subject(s) - physics , saturn , magnetosphere , brightness , astrophysics , population , electron , polar , flux (metallurgy) , zodiacal light , emission spectrum , ring current , astronomy , spectral line , plasma , planet , demography , materials science , quantum mechanics , sociology , metallurgy
Ultraviolet Hubble Space Telescope images reveal a faint but distinct auroral emission equatorward of the main ring of emission of Saturn's southern polar region. This outer auroral emission is only visible near the nightside limb for the strongly tilted viewing geometry achieved in January 2004. We model the limb‐brightening amplification of this emission, and we show that the observations are compatible with an ∼7° wide emission ring approximately centered on the 67°S parallel. The 1.7 kR brightness of this emission requires an injected electron energy flux of ∼0.3 mW m −2 . The outer auroral emission maps to a region of the equatorial plane between 4 and 11 R S . We suggest that a population of suprathermal electrons observed by Cassini can provide more than the required energy flux without the need for field‐aligned acceleration. This auroral UV emission may also be associated with energetic neutral oxygen and hydrogen atoms originating from the energetic protons and O + of magnetosphere and/or with a secondary infrared auroral oval.