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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 24, issue 11
Ann. Geophys., 24, 3139–3150, 2006
https://doi.org/10.5194/angeo-24-3139-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 24, 3139–3150, 2006
https://doi.org/10.5194/angeo-24-3139-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.

  22 Nov 2006

22 Nov 2006

Linear prediction studies for the solar wind and Saturn kilometric radiation

U. Taubenschuss1, H. O. Rucker1, W. S. Kurth2, B. Cecconi2, P. Zarka3, M. K. Dougherty4, and J. T. Steinberg5 U. Taubenschuss et al.
  • 1Space Research Institute, Austrian Academy of Sciences, A-8042 Graz, Austria
  • 2Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242, USA
  • 3Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Observatoire de Paris, 92195 Meudon, France
  • 4Blackett Laboratory, Imperial College of Science and Technology, London SW7 2BZ, UK
  • 5Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

Abstract. The external control of Saturn kilometric radiation (SKR) by the solar wind has been investigated in the frame of the Linear Prediction Theory (LPT). The LPT establishes a linear filter function on the basis of correlations between input signals, i.e. time profiles for solar wind parameters, and output signals, i.e. time profiles for SKR intensity. Three different experiments onboard the Cassini spacecraft (RPWS, MAG and CAPS) yield appropriate data sets for compiling the various input and output signals. The time period investigated ranges from DOY 202 to 326, 2004 and is only limited due to limited availability of CAPS plasma data for the solar wind. During this time Cassini was positioned mainly on the morning side on its orbit around Saturn at low southern latitudes. Four basic solar wind quantities have been found to exert a clear influence on the SKR intensity profile. These quantities are: the solar wind bulk velocity, the solar wind ram pressure, the magnetic field strength of the interplanetary magnetic field (IMF) and the y-component of the IMF. All four inputs exhibit nearly the same level of efficiency for the linear prediction indicating that all four inputs are possible drivers for triggering SKR. Furthermore, they act at completely different lag times ranging from ~13 h for the ram pressure to ~52 h for the bulk velocity. The lag time for the magnetic field strength is usually beyond ~40 h and the lag time for the y-component of the magnetic field is located around 30 h. Considering that all four solar wind quantities are interrelated in a corotating interaction region, only the influence of the ram pressure seems to be of reasonable relevance. An increase in ram pressure causes a substantial compression of Saturn's magnetosphere leading to tail collapse, injection of hot plasma from the tail into the outer magnetosphere and finally to an intensification of auroral dynamics and SKR emission. So, after the onset of magnetospheric compression at least ~1.2 rotations of the planet elapse until intensified SKR emission is visible in a Cassini-RPWS dynamic spectrum.

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