Bursty Bulk Flows and Substorm-Time Magnetotail Dynamics.
thesisposted on 29.06.2009, 12:16 by Colin Forsyth
I present three studies of magnetospheric tail dynamics associated with bursty bulk flows (BBFs) and substorms, concentrating on observations of the current systems of the BBFs and the dynamics of magnetotail current sheet waves. From a case study, I show that the observed magnetospheric current system of a BBF consisting of two flow bursts matched the current system predicted by Sergeev et al. (1996), and that the currents were consistent with previous studies. I also show that the particle signatures of the BBF were similar to the particle signatures in the PSBL prior to the BBF observations, demonstrating that the BBF was produced by the reconnection of lobe magnetic field-lines. From a survey of 628 BBF events, I show that BBF occurrence is highest during the recovery phase of substorms and lowest during non-substorm times and substorm growth phases. Using a subset of 211 BBF encounters that were sufficiently far from the magnetotail current sheet to determine the field-aligned currents, I show that the current magnitude is larger during the expansion and recovery phases of substorms than during the growth phase. Furthermore, the current magnitude is larger in the pre-midnight sector on large scale sizes. Utilising data from ground- and space-based observatories, I investigate an interval of current sheet wave activity following a solar wind pressure pulse and two substorms. By comparing the propagation of aurora and tail dipolarization signatures and the neutral sheet waves, I conclude that the propagation of these features is controlled by the same mechanism. I test two models of neutral sheet wave propagation and find that the model of Erkaev et al. (2008) gives a good fit to the data.