Articles | Volume 18, issue 9
Ann. Geophys., 18, 1097–1107, 2000

Special issue: IXe EISCAT

Ann. Geophys., 18, 1097–1107, 2000

  30 Sep 2000

30 Sep 2000

The dawn and dusk electrojet response to substorm onset

E. Borälv1, P. Eglitis1, H. J. Opgenoorth2,1, E. Donovan3, G. Reeves4, and P. Stauning5 E. Borälv et al.
  • 1Swedish Institute of Space Physics, Box 537, S-751 21 Uppsala, Sweden
  • 2Finnish Meteorological Institute, Geophysical Research, P.O. Box 503, FIN-00101 Helsinki, Finland
  • 3Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada T2N 1N4
  • 4Los Alamos National Laboratory, Mail Stop D-436, NM 87545, USA
  • 5Solar-Terrestrial Physics Division, Danish Meterological Institute, Lyngbyyvej 100, DK-2100 Copenhagen, Denmark
  • Correspondence to: E. Borälv
  • e-mail:

Abstract. We have investigated the time delay between substorm onset and related reactions in the dawn and dusk ionospheric electrojets, clearly separated from the nightside located substorm current wedge by several hours in MLT. We looked for substorm onsets occurring over Greenland, where the onset was identified by a LANL satellite and DMI magnetometers located on Greenland. With this setup the MARIA magnetometer network was located at dusk, monitoring the eastward electrojet, and the IMAGE chain at dawn, for the westward jet. In the first few minutes following substorm onset, sudden enhancements of the electrojets were identified by looking for rapid changes in magnetograms. These results show that the speed of information transfer between the region of onset and the dawn and dusk ionosphere is very high. A number of events where the reaction seemed to preceed the onset were explained by either unfavorable instrument locations, preventing proper onset timing, or by the inner magnetosphere's reaction to the Earthward fast flows from the near-Earth neutral line model. Case studies with ionospheric coherent (SuperDARN) and incoherent (EISCAT) radars have been performed to see whether a convection-induced electric field or enhanced conductivity is the main agent for the reactions in the electrojets. The results indicate an imposed electric field enhancement.

Key words: Ionosphere (auroral ionosphere; electric fields and currents) - Magnetospheric physics (storms and substorms)

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