Reference : Oscillation of Saturn's southern auroral oval
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
http://hdl.handle.net/2268/4550
Oscillation of Saturn's southern auroral oval
English
Nichols, J. D. [> > > >]
Clarke, J. T. [> > > >]
Cowley, S. W. H. [> > > >]
Duval, J. [> > > >]
Farmer, A. J. [> > > >]
Gérard, Jean-Claude mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) >]
Grodent, Denis mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) >]
Wannawichian, S. [> > > >]
2008
Journal of Geophysical Research
American Geophysical Union
113
A11
Yes (verified by ORBi)
International
0148-0227
Washington
DC
[en] Saturn ; magnetic field ; aurora
[en] Near-planetary-period oscillations in the Cassini plasma and magnetic field data have been observed throughout Saturn's magnetosphere despite the fact that Saturn's internal magnetic field is apparently highly axisymmetric. In addition, the period of the Saturn kilometric radiation has been shown to vary over time. In this paper we present results from the recent Hubble Space Telescope observations of Saturn's southern ultraviolet auroral emission. We show that the center of the auroral oval oscillates with period 10.76 h +/- 0.15 h for both January 2007 and February 2008, i.e., close to the periods determined for oscillations in other magnetospheric phenomena. The motion of the oval center is described for 2007 by an ellipse with semimajor axis similar to 1.4 degrees +/- 0.3 degrees oriented toward similar to 09-21 h LT, eccentricity similar to 0.93, and center offset from the spin axis by similar to 1.8 degrees toward similar to 04 h LT. For 2008 the oscillation is consistent with an ellipse with semimajor axis similar to 2.2 degrees +/- 0.3 degrees oriented toward similar to 09-21 h LT, eccentricity similar to 0.99, and a center offset from the spin axis by similar to 2.2 degrees toward similar to 03 h LT. The motion of the auroral oval is thus highly elliptical in both cases, and the major oscillation axis is oriented toward prenoon/premidnight. This result places an independent constraint on the magnitude of the planet's dipole tilt and may also indicate the presence of an external current system that imposes an asymmetry in the ionospheric field modulated close to the planetary period.
Researchers ; Professionals
http://hdl.handle.net/2268/4550
10.1029/2008JA013444

File(s) associated to this reference

Fulltext file(s):

FileCommentaryVersionSizeAccess
Restricted access
Nichols-Sat_oscil.pdfPublisher postprint981.13 kBRequest copy

Bookmark and Share SFX Query

All documents in ORBi are protected by a user license.