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Ann. Geophys., 17, 1574-1581, 1999
www.ann-geophys.net/17/1574/1999/
© European Geosciences Union 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
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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