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Ann. Geophys., 19, 1471-1481, 2001
www.ann-geophys.net/19/1471/2001/
© European Geosciences Union 2001
Multi-spacecraft observations of broadband waves near the lower hybrid frequency at the Earthward edge of the magnetopause
M. André1, R. Behlke1, J.-E. Wahlund1, A. Vaivads1, A.-I. Eriksson1, A. Tjulin1, T. D. Carozzi1, C. Cully1,2, G. Gustafsson1, D. Sundkvist1, Y. Khotyaintsev1, N. Cornilleau-Wehrlin3, L. Rezeau3, M. Maksimovic4, E. Lucek5, A. Balogh5, M. Dunlop5, P.-A. Lindqvist6, F. Mozer7, A. Pedersen8, and A. Fazakerley9
1Swedish Institute of Space Physics, Uppsala division, Sweden
2University of Calgary, Canada
3CETP, Vélizy, France
4DESPA/CNRS, Observatoire de Paris, Meudon, France
5The Blackett Laboratory, Imperial College, London, UK
6Royal Institute of Technology, Stockholm, Sweden
7Space Science Laboratory, University of California at Berkeley, Berkeley, USA
8Department of Physics, University of Oslo, Norway
9Mullard Space Science Laboratory, University College London, London, UK
Abstract. Broadband waves around
the lower hybrid frequency (around 10 Hz) near the magnetopause are studied,
using the four Cluster satellites. These waves are common at the Earthward edge
of the boundary layer, consistent with earlier observations, and can have
amplitudes at least up to 5 mV/m. These waves are similar on all four Cluster
satellites, i.e. they are likely to be distributed over large areas of the
boundary. The strongest electric fields occur during a few seconds, i.e. over
distances of a few hundred km in the frame of the moving magnetopause, a scale
length comparable to the ion gyroradius. The strongest magnetic oscillations in
the same frequency range are typically found in the boundary layer, and across
the magnetopause. During an event studied in detail, the magnetopause velocity
is consistent with a large-scale depression wave, i.e. an inward bulge of
magnetosheath plasma, moving tailward along the nominal magnetopause boundary.
Preliminary investigations indicate that a rather flat front side of the
large-scale wave is associated with a rather static small-scale electric field,
while a more turbulent backside of the large-scale wave is associated with
small-scale time varying electric field wave packets.
Key words. Magnetospheric physics
(magnetopause, cusp, and boundary layers) – Space plasma physics (waves and
in-stabilities)
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