Recurrent substorm activity during the passage of a corotating interaction region

Morley, S.K., Rouillard, A.P. and Freeman, M.P. (2009) Recurrent substorm activity during the passage of a corotating interaction region. Journal of Atmospheric and Solar-Terrestrial Physics, 71 (10-11), 1073-1081. (doi:10.1016/j.jastp.2008.11.009).

Record type: Article

Abstract

Recent observations of magnetospheric dynamics driven by interaction with both high-speed solar wind streams (HSSs) and interplanetary coronal mass ejections (ICMEs) have shown periodic substorms to be common under strong driving, but with different periods of 4 and 2–3 h, respectively. However, it is unclear what causes these substorms and what determines their periodicity. Observations during the passage of a corotating interaction region preceding a high-speed stream are presented here and the observed enhancements in the AE index are shown to be a quasi-periodic sequence of substorms. The occurrence times of these substorms and the variation of the AL index are shown to be consistent with a simple loading–unloading model without the need for external triggers. A possible explanation is given for the lengthening of the inter-substorm period during HSS relative to that of sawtooth events during ICMEs.

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