Articles | Volume 21, issue 8
Ann. Geophys., 21, 1807–1826, 2003
Ann. Geophys., 21, 1807–1826, 2003

  31 Aug 2003

31 Aug 2003

Coordinated interhemispheric SuperDARN radar observations of the ionospheric response to flux transfer events observed by the Cluster spacecraft at the high-latitude magnetopause

J. A. Wild1, S. E. Milan1, S. W. H. Cowley1, M. W. Dunlop2,†, C. J. Owen3, J. M. Bosqued4, M. G. G. T. Taylor*,3, J. A. Davies1, M. Lester1, N. Sato5, A. S. Yukimatu5, A. N. Fazakerley3, A. Balogh2, and H. Rème4,† J. A. Wild et al.
  • 1Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK
  • 2Blackett Laboratory, Imperial College, London SW7 2BZ, UK
  • 3Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
  • 4CESR, BP 4346, 31028 Toulouse 4, France
  • 5National Institute of Polar Research, Tokyo 173-8515, Japan
  • *now at: Los Alamos National Laboratory, Los Alamos, NM 87545, USA
  • now at: Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK

Abstract. At 10:00 UT on 14 February 2001, the quartet of ESA Cluster spacecraft were approaching the Northern Hemisphere high-latitude magnetopause in the post-noon sector on an outbound trajectory. At this time, the interplanetary magnetic field incident upon the dayside magnetopause was oriented southward and duskward (BZ negative, BY positive), having turned from a northward orientation just over 1 hour earlier. As they neared the magnetopause the magnetic field, electron, and ion sensors on board the Cluster spacecraft observed characteristic field and particle signatures of magnetospheric flux transfer events (FTEs). Following the traversal of a boundary layer and the magnetopause, the spacecraft went on to observe further signatures of FTEs in the magnetosheath. During this interval of ongoing pulsed reconnection at the high-latitude post-noon magnetopause, the footprints of the Cluster spacecraft were located in the fields-of-view of the SuperDARN Finland and Syowa East radars located in the Northern and Southern Hemispheres, respectively. This study extends upon the initial survey of Wild et al. (2001) by comparing for the first time in situ magnetic field and plasma signatures of FTEs (here observed by the Cluster 1 spacecraft) with the simultaneous flow modulations in the conjugate ionospheres in the two hemispheres. During the period under scrutiny, the flow disturbances in the conjugate ionospheres are manifest as classic "pulsed ionospheric flows" (PIFs) and "poleward moving radar auroral forms" (PMRAFs). We demonstrate that the ionospheric flows excited in response to FTEs at the magnetopause are not those expected for a spatially limited reconnection region, somewhere in the vicinity of the Cluster 1 spacecraft. By examining the large- and small-scale flows in the high-latitude ionosphere, and the inter-hemispheric correspondence exhibited during this interval, we conclude that the reconnection processes that result in the generation of PIFs/PMRAFs must extend over many (at least 4) hours of magnetic local time on the pre- and post-noon magnetopause.

Key words. Ionosphere (plasma convection) – Magnetospheric physics (magnetosphere-ionosphere interactions; magnetospheric configuration and dynamics)