Articles | Volume 16, issue 5
Ann. Geophys., 16, 549–565, 1998
Ann. Geophys., 16, 549–565, 1998

  31 May 1998

31 May 1998

SuperDARN studies of the ionospheric convection response to a northward turning of the interplanetary magnetic field

J. R. Taylor1, S. W. H. Cowley1, T. K. Yeoman1, M. Lester1, T. B. Jones1, R. A. Greenwald2, G. Sofko3, J.-P. Villain4, R. P. Lepping5, and M. R. Hairston6 J. R. Taylor et al.
  • 1Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
  • 2Applied Physics Laboratory, The Johns Hopkins University, Johns Hopkins Road, Laurel, Maryland 20723-6099, USA
  • 3Institute for Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan S7N 0W0, Canada
  • 4CNRS/LPCE, 3A Avenue de la Recherche Scientifique, 45701 Orléans Cedex 2, France
  • 5NASA Goddard Space Fight Center, Greenbelt, Maryland 20771, USA
  • 6W.B. Hansen Center for Space Sciences, University of Texas at Dallas, PO Box 830688, Richardson, Texas 75083, USA

Abstract. The response of the dayside ionospheric flow to a sharp change in the direction of the interplanetary magnetic field (IMF) measured by the WIND spacecraft from negative Bz and positive By, to positive Bz and small By, has been studied using SuperDARN radar, DMSP satellite, and ground magnetometer data. In response to the IMF change, the flow underwent a transition from a distorted twin-cell flow involving antisunward flow over the polar cap, to a multi-cell flow involving a region of sunward flow at high latitudes near noon. The radar data have been studied at the highest time resolution available (~2 min) to determine how this transition took place. It is found that the dayside flow responded promptly to the change in the IMF, with changes in radar and magnetic data starting within a few minutes of the estimated time at which the effects could first have reached the dayside ionosphere. The data also indicate that sunward flows appeared promptly at the start of the flow change (within ~2 min), localised initially in a small region near noon at the equatorward edge of the radar backscatter band. Subsequently the region occupied by these flows expanded rapidly east-west and poleward, over intervals of ~7 and ~14 min respectively, to cover a region at least 2 h wide in local time and 5° in latitude, before rapid evolution ceased in the noon sector. In the lower latitude dusk sector the evolution extended for a further ~6 min before quasi-steady conditions again prevailed within the field-of-view. Overall, these observations are shown to be in close conformity with expectations based on prior theoretical discussion, except for the very prompt appearance of sunward flows after the onset of the flow change.

Key words. Ionosphere (Auroral ionosphere) · Magnetospheric physics (Magnetopause · cusp · and boundary layers; Magnetosphere · ionosphere interaction)