Polar Ultraviolet Imager observation of auroral breakup

Abstract

The NASA's Polar satellite completed its mission in March 2008. During its 12 year operation, the Ultraviolet Imager (UVI) on-board Polar acquired a large number of auroral images in FUV bands with unprecedented spatial and temporal resolutions. The purpose of this brief report is to provide a list of auroral substorm onset identified with UVI to the community for full use. A total of 2003 auroral substorm onsets are identified in the Northern Hemisphere between 1996 and 2000 and 536 onsets in Southern Hemisphere in 2007. Distributions of the onset locations are near Gaussian, with a population mean of 65.9 (standard deviation = 2.2) in magnetic latitude (MLat) and 22.6 ( = 1.1) in magnetic local time (MLT) for the northern hemispheric events and 68.0 ( = 2.3) in MLat and 22.6 ( = 1.1) in MLT for the southern hemispheric events. A comparison with previously published IMAGE onset results suggests that substorms occur more frequently and intensely in the descending than in the ascending phase of solar cycle. The list of onset events includes the onset times and locations, and is provided as a supplement. Copyright 2010 by the American Geophysical Union.