IGPP Seminar Series

Magnetospheric Substorms: Observational Constraints on Trigger Models

by Prof. Shin Ohtani
Johns Hopkins University/APL


The trigger mechanism of magnetospheric substorms has been a focal issue of magnetospheric physics for many years. Associated phenomena such as auroral breakup, magnetic reconfiguration and particle injection in the near-Earth tail, and fast plasma flow in the plasma sheet have been studied extensively, and it is now widely accepted that magnetic reconnection and the reduction of the tail current are two fundamental processes of the substorm trigger. The former takes place most often in the mid-tail region (20~30 Re), whereas the latter is most manifest in the near-Earth (< 10 Re) region. However, it still remains to be understood how, or if, magnetic reconnection and tail current disruption are physically related. In the present talk I shall critically review two different ideas about causality between these two processes. A focus is placed on the outside-in model, the idea that magnetic reconnection is the very initial process of the substorm trigger. Although this model is more widely supported than the other model, the inside-out model, it has difficulties in explaining some basic features such as the sequence of auroral development and external trigger. I shall discuss such observational constraints that might be overlooked but should be implemented in future modeling efforts of the substorm trigger.
Tuesday, 14 November 2006
3845 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM