Interplanetary shock triggering of substorms: WIND and Polar Original Research Article

WIND solar wind data and POLAR UV imaging data are used to study magnetospheric responses to interplanetary shocks. It is found that the solar wind preconditions determine the different auroral responses. A ∼ 1.5 hr “precondition” (upstream of the interplanetary shocks) gives good empirical results. If the upstream IMF Bz is strongly southward preceding interplanetary shocks, a substorm expansion phase results (44% of all events). If the IMF Bz is ∼ 0, pseudobreakups occur. If Bz is northward, there is no obvious resultant nightside geomagnetic activity.