Global Alfvenic Interaction and Substorm Onset

Substorm onset is a result of Alfvenic interactions in the global current system including the tail and magnetopause current sheets as well as the auroral field-aligned current system. During the growth phase, the solar wind-magnetosphere interaction occurs in multiple regions throughout the magnetopause current sheets and stresses the tail current sheet, leaving it susceptible to the breakdown of the frozen-in condition. Changes in solar wind parameters or intrinsic tail plasma processes lead to a force imbalance that can often generate plasma flows and fast mode wave packets. These wave packets interact with the stressed current sheet and cause the breakdown of the frozen-in condition in multiple active localized regions throughout the tail current sheet. During this process and the further reconfiguration of the plasma sheet, Alfven waves carrying field aligned currents can be generated, which can cause auroral intensification and lead to the subsequent auroral development seen in the expansion phase. Observations predicted by this alternative Alfvenic interaction theory on substorm triggering and timing will be compared with the CD and NENL models.