Substorm onset observations by IMAGE‐FUV

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.