ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Springer Verlag Göttingen, Germany 10.1007/s00585-998-1105-7 ULF wave measurements onboard the Interball auroral probe Perraut S. 1 Roux A. 1 Darrouzet F. 1 de Villedary C. 1 Mogilevsky M. 2 Lefeuvre F. 3 CETP/UVSQ, 10-12 Av. de l'Europe, F-78140 Velizy, France<br>Fax: +1/39 25 49 22; e-mail: sylvaine.perraut@cetp.ipsl.fr Space Research Center, Profsoyuznaya 84/32, Moscow, Russia LPCE, 3A, Av. de la Recherche Scientifique, F-45071 Orleans cedex 2, France 30 09 1998 16 9 1105 1116 Copyright: © 1998 S. Perraut et al. 1998 © European Geosciences Union 1998 This article is available from https://angeo.copernicus.org/articles/16/1105/1998/angeo-16-1105-1998.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/16/1105/1998/angeo-16-1105-1998.pdf

The IESP experiment implemented onboard the Interball auroral probe measures the six components (3<i>B</i>, 3<i>E</i>) 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 <i>&#x03B2;<sub>i</sub></i> and by the O<sup>+</sup> concentration.<br><br><b>Key words. </b>Magnetospheric physics · Auroral phenomena · Plasma waves and instabilities · Interball Auroral probe</p>