Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 27, 885-894, 2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
23 Feb 2009
Quasiperiodic ULF-pulsations in Saturn's magnetosphere
G. Kleindienst1, K.-H. Glassmeier1,2, S. Simon3,*, M. K. Dougherty4, and N. Krupp2 1Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstraße 3, 38106 Braunschweig, Germany
2Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Straße 2, 37191 Katlenburg-Lindau, Germany
3Institut für Theoretische Physik, Technische Univ. Braunschweig, Mendelssohnstraße 3, 38106 Braunschweig, Germany
4The Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW, UK
*now at: Universität zu Köln, Institut für Geophysik und Meteorologie, Zülpicher Str. 49a, 50674 Köln, Germany
Abstract. Recent magnetic field investigations made onboard the Cassini spacecraft in the magnetosphere of Saturn show the existence of a variety of ultra low frequency plasma waves. Their frequencies suggest that they are presumably not eigenoscillations of the entire magnetospheric system, but excitations confined to selected regions of the magnetosphere. While the main magnetic field of Saturn shows a distinct large scale modulation of approximately 2 nT with a periodicity close to Saturn's rotation period, these ULF pulsations are less obvious superimposed oscillations with an amplitude generally not larger than 3 nT and show a package-like structure. We have analyzed these wave packages and found that they are correlated to a certain extent with the large scale modulation of the main magnetic field. The spatial localization of the ULF wave activity is represented with respect to local time and Kronographic coordinates. For this purpose we introduce a method to correct the Kronographic longitude with respect to a rotation period different from its IAU definition. The observed wave packages occur in all magnetospheric regions independent of local time, elevation, or radial distance. Independent of the longitude correction applied the wave packages do not occur in an accentuated Kronographic longitude range, which implies that the waves are not excited or confined in the same selected longitude ranges at all times or that their lifetime leads to a variable phase with respect to the longitudes where they have been exited.

Citation: Kleindienst, G., Glassmeier, K.-H., Simon, S., Dougherty, M. K., and Krupp, N.: Quasiperiodic ULF-pulsations in Saturn's magnetosphere, Ann. Geophys., 27, 885-894,, 2009.
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