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| Titel |
The latitudinal structure of the nightside outer magnetosphere of Saturn as revealed by velocity moments of thermal ions |
| VerfasserIn |
Z. Nemeth, K. Szego, L. Foldy, M. G. Kivelson, X. Jia, K. M. Ramer, S. W. H. Cowley, G. Provan, M. Thomsen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 33, no. 9 ; Nr. 33, no. 9 (2015-09-30), S.1195-1202 |
| Datensatznummer |
250121251
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| Publikation (Nr.) |
 copernicus.org/angeo-33-1195-2015.pdf |
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| Zusammenfassung |
| In this study we investigate the latitudinal behavior of the azimuthal
plasma velocities in the outer magnetosphere of Saturn using the numerical
ion moments derived from the measurements of the Cassini Plasma
Spectrometer. One of the new results presented is that although these
moments display some scatter, a significant positive correlation is found to
exist between the azimuthal velocity and the plasma density, such that on
average, the higher the density the higher the rotation speed. We also found
that both the azimuthal velocity and the density anticorrelate with the
magnitude of the radial component of the magnetic field and drop rapidly
with increasing distance from the magnetic equator. The azimuthal velocities
show periodic behavior with a period near the planetary rotation period,
which can also be explained by the strong dependence on magnetic latitude,
taking into account the flapping of the magnetodisk. It is thus found that
the dense plasma near the magnetic equator rotates around the planet at high
speed, while the dilute plasma at higher latitudes in the northern and
southern hemispheres rotates significantly slower. The latitudinal gradient
observed in the azimuthal speed is suggested to be a direct consequence of
the sub-corotation of the plasma in the outer magnetosphere, with highest
speeds occurring on field lines at lowest latitudes mapping to the rapidly
rotating inner regions of the plasma sheet, and the speed falling as one
approaches the lobe, where the field lines are connected to strongly
sub-corotating plasma. |
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