The Stability of Sunward Convection: A Triggering and Operative Mechanism for Substorms

摘要

In the 30 years since the substorm was first recognized as a distinct phenomenon, identification of the mechanism responsible for triggering the magnetospheric substorm has eluded the space physics community. In this paper, we wish to set forth the fundamental theoretical/physical context in which the substorm should be viewed. This is the context of M-I coupled convection and the compression of magnetospheric plasma. Within this context we argue that the process of substorm expansion is one in which a 'triggering' and an 'operative' mechanism need be distinguished. While we view the operative mechanism as near-Earth reconnection, we suggest a modified ballooning scenerio, involving a critical role for M-I coupling in the stability of the magnetospheric configuration, as a mechanism for triggering onset of the substorm expansion phase.