Reconnection, substorms and solar flares

We review the concept of a 'magnetic field reconfiguration' instability as the cause of solar flares and magnetospheric substorms. In this approach it is emphasized that it is not so much the need to break the frozen-field theorem but rather that the evolution of a magnetic field configuration, controlled by external influences, should lead to the formation of a neutral point somewhere within the configuration where magnetic field reconnection can Lake place rapidly in a manner which is controlled 'internally' and may therefore be catastrophic. (C) 1998 Elsevier Science Ltd. All rights reserved.