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Ann. Geophys., 16, 1105-1116, 1998
www.ann-geophys.net/16/1105/1998/
© European Geosciences Union 1998
ULF wave measurements onboard the Interball auroral probe
S. Perraut1, A. Roux1, F. Darrouzet1, C. de Villedary1, M. Mogilevsky2, and F. Lefeuvre3
1CETP/UVSQ, 10-12 Av. de l'Europe, F-78140 Velizy, France
Fax: +1/39 25 49 22; e-mail: sylvaine.perraut@cetp.ipsl.fr
2Space Research Center, Profsoyuznaya 84/32, Moscow, Russia
3LPCE, 3A, Av. de la Recherche Scientifique, F-45071 Orleans cedex 2, France
Abstract. The IESP experiment implemented onboard the
Interball auroral probe measures the six components (3B, 3E) of
the waves in the ULF range: 0.1–10 Hz and from time to time 0–30 Hz. Two
different kinds of waves have been observed in the auroral region at altitudes
between 10 000 and 20 000 km: (1) electrostatic emissions which consist of
quasi-monochromatic structures with frequencies above the oxygen gyrofrequency,
superimposed on a wide band signal interpreted as a Doppler broadening, (2)
electromagnetic wide band spectrum fluctuations. These emissions are interpreted
as current-driven electromagnetic or electrostatic ion cyclotron waves. The
electromagnetic/electrostatic character is controlled by the plasma parameter
βi and by the O+ concentration.
Key words. Magnetospheric physics · Auroral phenomena
· Plasma waves and instabilities · Interball Auroral probe
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