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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 10
Ann. Geophys., 14, 1032–1043, 1996
© European Geosciences Union 1996
Ann. Geophys., 14, 1032–1043, 1996
© European Geosciences Union 1996

  31 Oct 1996

31 Oct 1996

EISCAT/CRRES observations: nightside ionospheric ion outflow and oxygen-rich substorm injections

N. G. J. Gazey1, M. Lockwood1, M. Grande6,1, C. H. Perry1, P. N. Smith2, S. Coles2, A. D. Aylward3,1, R. J. Bunting4, H. Opgenoorth5, and B. Wilken7 N. G. J. Gazey et al.
  • 1Rutherford Appleton Laboratory, Chilton, Oxfordshire, OX11 0QX, UK
  • 2Space Science Centre, Sussex University, Falmer, BN1 9QH, UK
  • 3Atmospheric Physics Laboratory, UCL, London, W1P 7PP, UK
  • 4Department of Physics, York University, York, YO1 5DD, UK
  • 5Institutet för Rymdfysik, Uppsala, 75591 Uppsala, Sweden
  • 6Space Physics Department, Warwick University, Coventry, CV4 7AL, UK
  • 7Max-Planck Institut für Aeronomie, Katlenburg-Lindau, 37189, Germany

Abstract. We present combined observations made near midnight by the EISCAT radar, all-sky cameras and the combined released and radiation efects satellite (CRRES) shortly before and during a substorm. In particular, we study a discrete, equatorward-drifting auroral arc, seen several degrees poleward of the onset region. The arc passes through the field-aligned beam of the EISCAT radar and is seen to be associated with a considerable upflow of ionospheric plasma. During the substorm, the CRRES satellite observed two major injections, 17 min apart, the second of which was dominated by O+ ions. We show that the observed arc was in a suitable location in both latitude and MLT to have fed O+ ions into the second injection and that the upward flux of ions associated with it was sufficient to explain the observed injection. We interpret these data as showing that arcs in the nightside plasma-sheet boundary layer could be the source of O+ ions energised by a dipolarisation of the mid- and near-Earth tail, as opposed to ions ejected from the dayside ionosphere in the cleft ion fountain.

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