Depletion of electrons in a multiple substorm event

Using the IMAGE FUV instrumentation it is possible to determine the power of auroral events. Proton power can be calculated using the SI12 instrument and the power of the LBH spectrum can be calculated using the WIC camera. The resulting power spectrums can compared, examining the relationship of the precipitating particles. Data will be presented from a multiple substorm event from November 15, 2001. The multiple substorm event consists of two events that have no apparent IMF trigger during a strong southward IMF (-10 nT). These events are then followed by two substorm events that have external triggers (that being northward turnings). The peaks of the events starting at 1738 UT and 1815 UT have ratios of the SI-12/LBH power of roughly 45%, indicating that the aurora is primarily due to precipitating electrons. The breakup at 1900 UT has a peak of SI-12/LBH power of 170%. Clearly the protons make up much more of the particle precipitation into the auroral oval as the WIC images show weak intensities likely related to secondary electrons from the proton precipitation. The recovery phase after this final substorm is quick for the LBH power but the proton power shows that the decay is longer, perhaps even with another event occurring at 2140 UT with only a proton power signature. Loss cone for the electrons means they are favoured to precipitate into the oval but are depleted in the later substorm and protons make up the majority of the precipitating particles. Particle measurements will be used in conjunction with images from IMAGE FUV instruments to help determine the relationship between the protons and electrons in this multiple substorm event scenario. Key words: substorms, IMAGE FUV, multiple events