Global Observations of Exospheric Temperature During the Bastille Day Event and Comparisons With the MTIEGCM Model and NRLMSIS-2000

We present observations of the global exospheric temperature and its variation during the Bastille Day geomagnetic storm that occurred on July 14-18, 2000. The Bastiile Day event was initiated by an X-class solar flare that was followed by a coronal mass ejection. The CME eventually produced a major geomagnetic storm. Global exospheric temperatures were derived by fitting the topside intensity distribution of limb scan data observed by the Low Resolution Airglow and Aurora Spectrograph (LORAAS) on the Advanced Research and Global Observation Satellite (ARGOS). The ARGOS was launched into a sun-synchronous orbit on 23 February 1999 at 2:29:55 AM Pacific Standard Time. The LORAAS obtained limb scans every 90 seconds providing soundings spaced by approximately 5.4° of latitude. We compare the LORAAS-derived exospheric temperatures with exospheric temperatures predicted by the Mass Spectrometer and Incoherent Scatter (MSIS) with Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (MTIEGCM). We find that the measured temperatures are systematically higher, by ~200 K, than predicted by the NRLMSIS-2000 model and the temporal evolution of the temperature changes is also not well reproduced by the model. The MTIEGCM model, with its more accurate picture of the geomagnetic and solar effects, is shown to better capture both the time evolution of the storm-time temperature changes and to also more accurately predict the quiet time temperatures.