Articles | Volume 17, issue 12
Ann. Geophys., 17, 1574–1581, 1999

Special issue: Equator S

Ann. Geophys., 17, 1574–1581, 1999

  31 Dec 1999

31 Dec 1999

Magnetopause boundary structure deduced from the high-time resolution particle experiment on the Equator-S spacecraft

G. K. Parks1, S. Datta1, M. McCarthy1, R. P. Lin2, H. Reme3, J. A. Sauvaud3, T. Sanderson4, W. Baumjohann5, G. Haerendel5, and K. Torkar6 G. K. Parks et al.
  • 1Geophysics Program, Box 351650, University of Washington, Seattle, WA
  • 2Space Science Laboratory, UC Berkeley, Berkeley, CA
  • 3CESR, Paul Sabatier University, Toulouse, France
  • 4European Space Agency, Noordwijk, The Netherlands
  • 5Max Planck Institute for Extraterrestrial Physics, Garching, Germany
  • 6Space Research Institute, Inffeldgasse 12, A-8010, Graz, Austria

Abstract. An electrostatic analyser (ESA) onboard the Equator-S spacecraft operating in coordination with a potential control device (PCD) has obtained the first accurate electron energy spectrum with energies ≈7 eV–100 eV in the vicinity of the magnetopause. On 8 January, 1998, a solar wind pressure increase pushed the magnetopause inward, leaving the Equator-S spacecraft in the magnetosheath. On the return into the magnetosphere approximately 80 min later, the magnetopause was observed by the ESA and the solid state telescopes (the SSTs detected electrons and ions with energies ≈20–300 keV). The high time resolution (3 s) data from ESA and SST show the boundary region contains of multiple plasma sources that appear to evolve in space and time. We show that electrons with energies ≈7 eV–100 eV permeate the outer regions of the magnetosphere, from the magnetopause to ≈6Re. Pitch-angle distributions of ≈20–300 keV electrons show the electrons travel in both directions along the magnetic field with a peak at 90° indicating a trapped configuration. The IMF during this interval was dominated by Bx and By components with a small Bz.

Key words. Magnetospheric physics (magnetopause · cusp · and boundary layers; magnetospheric configuration and dynamics; solar wind · magnetosphere interactions)

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