Articles | Volume 26, issue 8
Ann. Geophys., 26, 2485–2502, 2008

Special issue: 13th International EISCAT Workshop

Ann. Geophys., 26, 2485–2502, 2008

  20 Aug 2008

20 Aug 2008

Ion-dispersion and rapid electron fluctuations in the cusp: a case study

J. Lunde1, S. C. Buchert2, Y. Ogawa3, M. Hirahara4, K. Seki5, Y. Ebihara6, T. Sakanoi7, K. Asamura8, M. Okada3, T. Raita9, and I. Häggström10 J. Lunde et al.
  • 1Department of Physics and Technology, University of Tromsø, Norway
  • 2Swedish Institute of Space Physics, University of Uppsala, Sweden
  • 3National Institute of Polar Research (NIPR), Tokyo, Japan
  • 4Department of Earth and Planetary Science, University of Tokyo, Japan
  • 5STEL, Nagoya University, Japan
  • 6IAR, Nagoya University, Japan
  • 7PPARC, Tohoku University, Japan
  • 8ISAS/JAXA, Sagamihara, Japan
  • 9Sodankylä Geophysical Observatory, University of Oulu, Finland
  • 10EISCAT Scientific Association, Kiruna, Sweden

Abstract. We present results from co-ordinated measurements with the low altitude REIMEI satellite and the ESR (EISCAT Svalbard Radar), together with other ground-based instruments carried out in February 2006. The results mainly relate to the dayside cusp where clear signatures of so-called ion-dispersion are seen in the satellite data. The cusp ion-dispersion is important for helping to understand the temporal and spatial structure of magnetopause reconnection. Whenever a satellite crosses boundaries of flux tubes or convection cells, cusp structures such as ion-dispersion will always be encountered. In our case we observed 3 distinct steps in the ion energy, but it includes at least 2 more steps as well, which we interpret as temporal features in relation to pulsed reconnection at the magnetopause. In addition, fast variations of the electron flux and energy occurring during these events have been studied in detail. The variations of the electron population, if interpreted as structures crossed by the REIMEI satellite, would map near the magnetopause to similar features as observed previously with the Cluster satellites. These were explained as Alfvén waves originating from an X-line of magnetic reconnection.