Substorm onset observations by IMAGE-FUV: 2003-2005

Frey, H.U., S.B. Mende


Following a previous study of substorm onset observations by the FUV instrument
on the IMAGE spacecraft between 2000-2002 (Frey et al., 2004] this report
extends the investigation to the time period of January 1, 2003 to March 31,
2005.  Due to the precession of the IMAGE orbit and long times spent at apogee
around the equator with unfavorable viewing conditions for the exact
determination of the onset location, only 1301 substorm onsets could be observed
during this time period, compared to almost twice as many in the first
investigation.  However, almost 75% of the onsets were observed in the southern
hemisphere compared to only northern hemisphere onsets in the first study.  The
average onset magnetic local time and absolute values of magnetic latitude are
exactly the same as in the first study despite the different periods within the
solar cycle and slightly different average IMF conditions. Here again we publish
the list of onsets to allow for further investigation.

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Submitted to Journal of Geophysical Research, 2005JA011564, 2005