Authors

L. R. Lyons
Department of Atmospheric Sciences
University of California, Los Angeles
Los Angeles, CA 90095-1565

I. O Voronkov
Department of Physics, University of Alberta
Edmonton, Alberta T6G 2J1, Canada

J. M. Ruohoniemi
Johns Hopkins University, Applied Physics Laboratory
11100 Johns Hopkins Rd., Laurel, MD 20723-6099

and

E. F. Donovan
Department of Physics and Astronomy, University of Calgary
Calgary, Alberta T2N 1N4, Canada

Invited ipaper based on presentation at the Sixth International Conference on Substorms
in Sixth International Conference on Substorms, ed. by M. M. Winglee, p. 47, University of Washington, Seattle, 2002

Abstract

Auroral breakup at substorm onset often is observed along a new arc that forms a few minutes prior to the time traditionally identified as substorm onset. The breakup arc increases in intensity approximately monotonically prior to onset and then becomes non-linear at onset, suggesting that the magnetosphere undergoes a transition to an unstable configuration a few minutes prior to onset and that the resulting instability is responsible for the substorm expansion phase. A reduction in the strength of dayside convection is also often observed to initiate few minutes prior onset, and we suggest that this reduction causes the magnetosphere to make the transition from stability to instability. If this inference is correct, then the critical outstanding question concerning substorms is how does a convection reduction cause the transition to instability and how does this transition lead to formation of the breakup arc prior to onset and to the substorm current wedge.

All full manuscripts and figures are available in PDF format only. For another format or hardcopies you will need to contact the Authors.

Paper (pdf format)