Articles | Volume 24, issue 12
21 Dec 2006
 | 21 Dec 2006

Global manifestations of a substorm onset observed by a multi-satellite and ground station network

H. Wang, S. Y. Ma, H. Lühr, Z. X. Liu, Z. Y. Pu, C. P. Escoubet, H. U. Frey, H. Réme, and P. Ritter

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.