Milan, S. E. and Wild, J. A. and Hubert, B. and Carr, C. M. and Lucek, E. and Bosqued, J. M. and Watermann, J. F. and Slavin, J. A. (2006) Flux transport and tail dynamics during a prolonged substorm interval. In: Proceedings of the Cluster and Double Star Symposium: 5th Anniversary of Cluster in Space, 2005-09-192005-09-23.
Abstract
We present multi-point observations of a substorm which took place on 29 August 2004. The near-Earth magnetotail dynamics were observed by Cluster C1 and Double Star TC1, in conjunction with observations of the Northern Hemisphere ionospheric convection flow from the Super Dual Auroral Radar Network (Super- DARN), of the Southern Hemisphere auroral morpholo- gy from the Wideband Imaging Camera of the Far Ul- traviolet instrument onboard the Imager for Magneto- pause-to-Aurora Global Exploration spacecraft (IMAGE FUV/WIC), and of ionospheric substorm currents from the Greenland magnetometer chain. Following the substorm growth phase, expansion phase onset results in the closure of open magnetic flux for 3 hours, prolonged by continued creation of open flux at the dayside. The 3-hour duration of the substorm was punctuated by 5 dipolarizations which we interpret as individual bursts of reconnection, each closing ~0.125 GWb of flux. As- sociated with each dipolarization were auroral en- hancements, convection enhancements and a step-wise poleward progression of the substorm current wedge. We derive the amount of open flux in the magnetos- phere from observations of the ionospheric polar cap, along with the corresponding rates of dayside and night- side reconnection. From these we can model the chang- ing length of the magnetotail and variations in its radius, flaring, and lobe field strength during the course of the growth and expansion phases of the substorm. Despite the simplicity of this modeling, we demonstrate good agreement between predicted lobe field strength and the observations of Cluster.