ULF wave measurements onboard the Interball auroral probe
- 1CETP/UVSQ, 10-12 Av. de l'Europe, F-78140 Velizy, France
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- 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