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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 31, issue 10
Ann. Geophys., 31, 1721–1730, 2013
https://doi.org/10.5194/angeo-31-1721-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 31, 1721–1730, 2013
https://doi.org/10.5194/angeo-31-1721-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 16 Oct 2013

Regular paper | 16 Oct 2013

Comparative time-series analysis of MeV electron data by Ulysses and Pioneer 10/11 in the Jovian magnetosphere

P. Dunzlaff1,2, B. Heber2, A. Kopp1,2, and M. S. Potgieter1 P. Dunzlaff et al.
  • 1Centre for Space Research, North-West University, Potchefstroom, South Africa
  • 2Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Kiel, Germany

Abstract. The dynamics of the Jovian magnetosphere is dominated by the planet's fast rotation with a period of ~ 10 h. Within the magnetosphere, this periodicity can in particular be seen in the temporal variation of the spectral index of MeV electrons: every ~ 10 h the counting rates show a maximum (minimum), while the spectral index shows a minimum (maximum) known as the Jovian "clock" mechanism. In this study we re-analyse Ulysses and Pioneer 10/11 data and show that another periodic modulation in the MeV electrons can be identified, manifested by local maxima of the spectral index and local minima of the counting rates. For Ulysses, this modulation can be observed throughout the magnetosphere near the magnetic equator, suggesting an azimuthal asymmetric distribution of MeV electrons near the current sheet. This modulation is found to trail the "clock" mechanism by ~ 3.25 h. The Pioneer 10 data, however, only show occasional evidence of the presence of these local maxima while there is no evidence of this modulation in the Pioneer 11 data. A comparison of the times of observed minor peaks and Ulysses' distance from the current sheet using a simple rigid disc model as well as the model of Khurana and Schwarzl (2005) is performed.

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