[en] The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms(1), but the relation between the solar wind and the dynamics of the outer planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system(2), whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging(3) we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Crary, Frank J.; Southwest Research Institute (Texas)
Clarke, John T.; Boston University
Dougherty, Michele K.; Imperial College of Science and Technology (London) > Blackett Laboratory
Hanlon, P. G.; Imperial College of Science and Technology (London) > Blackett Laboratory
Hansen, K. C.; University of Michigan > Space Research Building
Steinberg, John T.; Los Alamos National Laboratory
Barraclough, B. L.; Los Alamos National Laboratory
Coates, Andrew J.; University College London > Mullard Space Science Laboratory
Grodent, Denis ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Kurth, William S.; University of Iowa > Department of Physics and Astronomy
Mitchell, D. G.; Johns Hopkins University > Applied Physics Laboratory
Rymer, A. M.; University College London > Mullard Space Science Laboratory
Young, David T.; Southwest Research Institute (Texas)
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