Statistical comparison of isolated and non-isolated auroral substorms

We present results from a superposed epoch analysis of the morphology and energy deposition of isolated and non-isolated auroral substorms. The study is based on auroral data acquired by the global ultraviolet imager (GUVI) on board the TIMED satellite and a total number of 13717 geomagnetic bay onsets identified with magnetometer data from SuperMAG and published previously by Newell and Gjerloev [2011]. Here the isolated substorms are those having separation of two consecutive onsets no less than 3 hours. While the three phases substorm are clearly shown in both isolated and non-isolated substorms, there are noticeable differences between the two types of substorms: (1) In the growth phase, the nighttime auroral power slightly increases for both types of substorms; isolated (non-isolated) substorms are associated with smaller (greater) nighttime auroral power; (2) In the expansion phase, substorm energy release is greater and more explosive for isolated than non-isolated substorms; (3) The recovery phase period is longer for isolated than for non-isolated substorms; (4) The winter-to-summer auroral power ratio is approximately constant throughout the three substorm phases and the ratio is larger for isolated (30%) than for non-isolated (20%) substorms. We also found that the polar cap area increases during the growth phase until ~10 min prior to the magnetic substorm onset and decreases rapidly after onset. The decrease is associated with the closure of the nightside auroral oval associated with substorm expansion. We found most of these differences can be related to the differences in their solar wind driving. We will present the results in detail and make a conclusion.