Global auroral response to a solar wind pressure pulse

A global intensification of the aurora was observed by the Ultraviolet Imager on the NASA Polar spacecraft in conjunction with the arrival of the sheath from a solar coronal mass ejection. The aurora was first observed to brighten on the dayside and then the intensification progressed rapidly toward the nightside. During this time the IMP-8 spacecraft in the solar wind recorded a 35-minute period of increased solar wind dynamic pressure. A small substorm (or, possibly pseudobreakup) occurred within a minute of the arrival of the auroral intensification on the nightside in conjunction with a second peak in the dynamic pressure. We propose that the intensification of the aurora can be explained on the basis of the compression of the magnetopause and the generation of hydromagnetic waves by the rapid increase in the solar wind dynamic pressure. It is also evident that the substorm was triggered by waves, generated by a second rise in the dynamic pressure, that propagated to flux tubes connected to the premidnight auroral region. (C) 2000 COSPAR. Published by Elsevier Science Ltd.