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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 5
Ann. Geophys., 22, 1765–1771, 2004
https://doi.org/10.5194/angeo-22-1765-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 1765–1771, 2004
https://doi.org/10.5194/angeo-22-1765-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  08 Apr 2004

08 Apr 2004

Evidence for storm-time ionospheric ion precipitation in the cusp with magnetosheath energy

H. Stenuit and J.-A. Sauvaud H. Stenuit and J.-A. Sauvaud
  • CESR/CNRS, 9 av. du colonel Roche, 31028 Toulouse, France

Abstract. We present evidence for a sporadic precipitation into the north polar cusp of ionospheric O+ and He+ ions accelerated up to the magnetosheath flow speed during a magnetic storm. This is deduced from data obtained on board the Interball-Auroral satellite showing that the energy/charge ratios of the H+, He++, He+ and O+ populations are similar to those of ion masses. These measurements pertain to a very disturbed magnetic period. A storm was in progress with a Dst reaching -149nT during the cusp measurements, while the AE index reached values higher than 1000nT. This result is discussed in terms of ion circulation from the magnetosphere to the magnetosheath and back to the magnetosphere. We suggest that the acceleration of O+ and He+ ions up to a magnetosheath-like velocity is directly linked to the large By component of the IMF.

Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; magnetosheath; storms and substorms)

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