Energetic and Dynamic Coupling of the Magnetosphere-Ionosphere-Thermosphere System

This paper illustrates several important energetic and dynamic processes taking place within the magnetosphereionosphere- thermosphere system during the October 2003 geomagnetic storms. Numerical simulations based on the National Center for Atmospheric Research - Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (NCAR-TIMEGCM) were carried out to assess the relative impact of various solar and magnetospheric forcings. The model showed a significant increase of thermospheric temperature in response to Joule heating dissipation during the storms, from about 30% (or 400°K) above 400 kilometers (km) to about 10% (or ~100°K) at 150 km. Thermospheric mass density exhibited similar altitude dependence in its stormtime response, with an increase of more than 150% above 400 km to about 30% at 150 km. Around 100 km, thermospheric storm effects became indiscernible. Intense auroral and Joule heating dissipation altered the F-region peak density NmF₂ and raised the peak height hmF₂. Energetic particle precipitation not only increases the E- and D-region conductivity but also enhances Joule and particle heating in these regions. The NO_X enhancement and ozone (O₃) destruction resulting from solar energetic protons (SEP) were seen throughout the rest of year 2003 following the Halloween storms. Significant hemispheric asymmetry was found, in that the SEP-related NO_X and O₃ changes were more pronounced in the northern hemisphere than in the southern hemisphere.