Sawtooth-substorm connections: A closer look

Abstract

[1] This paper seeks to improve understanding of sawtooth events (STEs) that occur during the main phases of geomagnetic storms. We consider the dynamics of diverse space environments encountered during a magnetic storm on 24 March 2002 when four STEs were identified in energetic particle fluxes measured by Synchronous Orbit Particle Analyzers on Los Alamos National Laboratory satellites. Over the reported interval, 28 substorms were identified in magnetometer traces obtained via the SuperMAG international collaboration. Magnetic inclination variations sampled by the Geostationary Operational Environment Satellites 8 and 10 on the nightside indicate that STEs coincided with substorms marked by strong and prolonged dipolarizations. Significantly, the four STEs were accompanied by partial recoveries of the SYM-H index. Two SuperMAG substorms were marked by weak dipolarizations and energetic particle flux increases. The remaining 22 substorms showed no such signatures near 6.6 RE. We regard the latter SuperMAG events as indicating intensifications of the DP 2 current system driven by episodically enhanced reconnection at the distant X line. Presented data are shown to be consistent with the conjecture of Huang et al. (2009) that STEs occur only after open flux in the magnetotail exceeds a critical level near 109 Wb. During STEs, significant quantities of open flux were removed from the magnetotail at near-Earth reconnection lines. It took ~3 h to eject plasmoids and replenish open flux in the magnetotail to a critical level via continued dayside merging, thereby driving quasi-cyclic STE occurrences.