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

• Main Authors: Gazey, N. G. J., Lockwood, M., Grande, M., Perry, C. H., Smith, P. N., Coles, S., Aylward, A. D., Bunting, R. J., Opgenoorth, H., Wilken, B.
• Other Authors: STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Space Physics Department, University of Warwick Coventry, Space Science Centre, University of Sussex, Atmospheric Physics Laboratory UCL London, University College of London London (UCL), Department of Physics, York University Toronto, Institutet för Rymdfysik, Max-Planck-Institut für Aeronomie (MPI Aeronomie), Max-Planck-Gesellschaft
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1996
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; EISCAT
• Online Access: https://hal.science/hal-00316204; https://hal.science/hal-00316204/document; https://hal.science/hal-00316204/file/angeo-14-1032-1996.pdf

International audience 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.