Article (Scientific journals)
Variable morphology of Saturn's southern ultraviolet aurora
Grodent, Denis; Gérard, Jean-Claude; Cowley, S. W. H. et al.
2005In Journal of Geophysical Research. Space Physics, 110 (A7)
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Abstract :
[en] The Space Telescope Imaging Spectrograph camera on board Hubble Space Telescope obtained 68 FUV images of Saturn's southern auroral emission between 8 and 30 January 2004, during Cassini's approach to Saturn's magnetosphere. The HST observations took place in four different solar wind regimes with a low-field rarefaction region from 8 to 16 January, a minor compression event on 17 January, a rarefaction region with intermediate field strengths from 19 to 25 January, and a major compression region from 26 to 30 January. The images have been projected onto polar maps in order to characterize and compare the general morphology of the auroral emission. The first 20 images were obtained during a period covering about 70% of one full rotation of Saturn. They show that the bright ring of auroral emission actually consists of several arcs of different width and brightness and forming along different parallels. Overall, the auroral region is shown to rotate at similar to 65% of the full planetary rotation, although the angular velocity of some isolated auroral structures constantly decrease with time, down to 20%. The strongest auroral precipitations are observed in the morning sector. The polar projections of the 48 remaining images confirm dramatic changes in morphology, characterized by different average zones. During the campaign, short intervals during which the auroral region is significantly contracted and clearly forms a spiral were followed by intervals of reinflation of the auroral region. It is suggested that the two major auroral contraction events corresponded to the arrival of the solar wind shocks observed by Cassini on 17 January and 25 January. The present analysis indicates that Saturn's auroral morphology responds to the solar wind conditions at Saturn.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Grodent, Denis  ;  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.
Cowley, S. W. H.
Bunce, E. J.
Clarke, J. T.
Language :
English
Title :
Variable morphology of Saturn's southern ultraviolet aurora
Publication date :
15 July 2005
Journal title :
Journal of Geophysical Research. Space Physics
ISSN :
2169-9380
eISSN :
2169-9402
Publisher :
Amer Geophysical Union, Washington, United States - Washington
Volume :
110
Issue :
A7
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
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