Relations Between Bursty Bulk Flows in the Magnetotail and Substorms

Abstract

By using the data of three satellites of Cluster from 2001 to 2002, we study BBFs in the magnetotail and its relation to substorms. It is found that sometimes one or two of three satellites have already observed the BBF, and however the rest haven't. The reasons are as follows: (1) while the bulk flows satisfy the selection criterion of BBFs, the satellite isn't in the region requested in the rule; (2) while the satellite is in the central plasma sheet, the bulk flows don't satisfy. Since BBFs are highly localized, they are very difficult to be observed by all satellites. The whole durations of BBFs observed by C1, C3, C4 account for 55.07%, 77.48%, and 55.52% of that observed by three satellites jointly. Statistical studies indicate that most substorms are accompanied by one or more BBF events. Only a few substorms are not accompanied by BBF events, which may be caused by: (1) the satellite isn't in the region requested in the selection rule; (2) the structure and motion of neutral sheet are complicated, (3) the BBF selection criteria are arbitral and limited; (4) BBF events are highly localized.