Global manifestations of a substorm onset observed by a multi-satellite and ground station network
Escoubet, C. P.; Liu, Z. X.; Frey, H. U.; Réme, H.; Wang, H.; Lühr, H.; Pu, Z. Y.; Ritter, P.; Ma, S. Y.
China, United States, Germany, Netherlands, France
Abstract
With a favorable constellation of spacecraft and ground stations, a study is made on the global manifestations of a substorm onset. The onset occurred simultaneously and conjugately in both hemispheres, confirmed by observations of the auroral breakup from IMAGE FUV-WIC and a sudden intensification of a westward electrojet from ground-based magnetometers. Concurrently with the onset, field-aligned and Hall currents in the auroral ionosphere are observed by CHAMP, which are consistent with the signature of a Harang discontinuity. Immediately after the onset a magnetic field dipolarization is clearly observed by Double Star TC-1, located near the central magnetotail and subsequently, by the Cluster quartet. The observations can be explained by a dawnward propagation of the substorm current wedge at a speed of about 300 km/s.