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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 4
Ann. Geophys., 22, 1297–1304, 2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 1297–1304, 2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  02 Apr 2004

02 Apr 2004

Multiple discrete-energy ion features in the inner magnetosphere: 9 February 1998, event

Y. Ebihara1, M. Ejiri1, H. Nilsson2,3,4, I. Sandahl2,3,4, M. Grande3,4, J. F. Fennell4,5,6, J. L. Roeder4,5, D. R. Weimer5,6, and T. A. Fritz6 Y. Ebihara et al.
  • 1National Institute of Polar Research, Tokyo, Japan
  • 2Swedish Institute of Space Physics, Kiruna, Sweden
  • 3Rutherford Appleton Laboratory, Chilton, Didcot, UK
  • 4The Aerospace Corporation, Los Angeles, California, USA
  • 5Mission Research Corp., Nashua, New Hampshire, USA
  • 6Boston University, Boston, Massachusetts, USA

Abstract. Multiple discrete-energy ion bands observed by the Polar satellite in the inner magnetosphere on 9 February 1998 were investigated by means of particle simulation with a realistic model of the convection electric field. The multiple bands appeared in the energy vs. L spectrum in the 1–100 keV range when Polar traveled in the heart of the ring current along the outbound and inbound paths. We performed particle tracing, and simulated the energy vs. L spectra of proton fluxes under the dipole magnetic field, the corotation electric field, and the realistic convection electric field model with its parameters depending on the solar wind data. Simulated spectra are shown to agree well with the observed ones. A better agreement is achieved when we rotate the convection electric potential eastward by 2h inMLT and we change the distribution function in time in the near-Earth magnetotail. It is concluded that the multiple bands are likely produced by two processes for this particular event, that is, changes in the convection electric field (for >3keV protons) and changes in the distribution function in the near-Earth magnetotail (for <3keV protons).

Key words. Magnetospheric physics (energetic particles, trapped; electric field) – Space plasma physics (numerical simulation studies)

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