Substorm onset observations by IMAGE-FUV

H. U. Frey, S. B. Mende, V. Angelopoulos, and E. F. Donovan


Over the first 2.5 years of operation, the FUV instrument on the IMAGE 
spacecraft observed more than 2400 substorm onsets in the Northern 
Hemisphere. The observations confirm earlier results of statistical studies 
in terms of a median substorm onset location at 2300 hours MLT and 66.4 
degrees magnetic latitude. The purpose of this report is to publish the list 
to allow for further investigation. The list can easily be searched for 
onsets close to certain ground stations or at specific magnetic latitudes or 
local times.  As one example of such use we demonstrate how the probability 
of onset observation was determined for the ground-based automatic 
observatories of the THEMIS (Time History of Events and Macroscale 
Interactions during Substorms) project.

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Accepted, Journal of Geophysical Research, 2004