Ann. Geophysicae 18, 1097±1107 �2000) Ó EGS ± Springer-Verlag 2000 The dawn and dusk electrojet response to substorm onset

• Main Authors: E. Boraè Lv, P. Eglitis, H. J. Opgenoorth, E. Donovan, G. Reeves, P. Stauning
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: more localized substorm current wedge. The convection; Greenland; EISCAT
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.371.4530; http://hal.archives-ouvertes.fr/docs/00/31/67/82/PDF/angeo-18-1097-2000.pdf

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 identi®ed 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 ®rst few minutes following substorm onset, sudden enhancements of the electrojets were identi®ed 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 ¯ows from the near-Earth neutral line model. Case studies with ionospheric coherent �SuperDARN) and incoherent �EISCAT) radars have been performed to see whether a convectioninduced electric ®eld or enhanced conductivity is the main agent for the reactions in the electrojets. The results indicate an imposed electric ®eld enhancement.