Fig. 1From: EUV signals associated with O+ ions observed from ISS-IMAP/EUVI in the nightside ionosphereEUV image taken from EUVI-B during 21:08:26–21:09:25 UT (a) and 21:18:38–21:19:37 UT (b) on December 26, 2012. The red square in each panel indicates the region where the EUV count is averaged to obtain Fig. 3. The orange contours in each panel indicate the altitude (in \({\mathrm km}\)) at the tangential point along the line of sightBack to article page