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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 4
Ann. Geophys., 16, 403–412, 1998
https://doi.org/10.1007/s00585-998-0403-4
© European Geosciences Union 1998
Ann. Geophys., 16, 403–412, 1998
https://doi.org/10.1007/s00585-998-0403-4
© European Geosciences Union 1998

  30 Apr 1998

30 Apr 1998

Article: Heating of beam ions by ion acoustic waves

A. Vaivads, K. Rönnmark, T. Oscarsson, and M. André A. Vaivads et al.
  • Swedish Institute of Space Physics, University of Umeå , S-901 87 UMEÅ , Sweden

Abstract. Satellite measurements show that ion beams above the auroral acceleration region are heated to hundreds of eV in a direction perpendicular to the magnetic field. We show that ion acoustic waves may be responsible for much of this heating. Even in the absence of a positive slope in the velocity distribution of the beam ions, ion acoustic waves can be generated by a fan instability. We present analytical estimates of the wave growth rate and ion beam heating rate. These estimates, which are confirmed by particle simulations, indicate that the perpendicular temperature of the beam ions will increase by 30 eV/s, or by 1 eV in 20–25 km. From the simulations we also conclude that the heating saturates at a perpendicular temperature around 200 eV, which is consistent with observations.

Key words. Ionosphere (wave-particle interactions) · Magnetospheric Physics (plasma waves and instabilities) · Space plasma physics (wave-particle interactions).

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