On the origin of Saturn's outer auroral emission

Planetary Sciences: Solar System Objects: Saturn; Planetary Sciences: Fluid Planets: Aurorae; Magnetospheric Physics: Planetary magnetospheres (5443; 5737; 6033); Magnetospheric Physics: Energetic particles: precipitating; Magnetospheric Physics: Auroral phenomena (2407)

Abstract :

[en] 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[SUP]‑2[/SUP]. The outer auroral emission maps to a region of the equatorial plane between 4 and 11 R[SUB]S[/SUB]. 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[SUP]+[/SUP] of magnetosphere and/or with a secondary infrared auroral oval.

Disciplines :

Space science, astronomy & astrophysics

Author, co-author :

Grodent, Denis ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)

Radioti, Aikaterini ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)

Bonfond, Bertrand ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)

Gérard, Jean-Claude ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)

Language :

English

Title :

On the origin of Saturn's outer auroral emission

Publication date :

2010

Journal title :

Journal of Geophysical Research. Space Physics

ISSN :

2169-9380

eISSN :

2169-9402

Publisher :

Wiley, Hoboken, United States - New Jersey

Volume :

115

Pages :

08219

Peer reviewed :

Peer Reviewed verified by ORBi

Available on ORBi :

since 10 November 2010

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