Impacts of Ionospheric Conductance on Magnetosphere-Ionosphere Coupling

Understanding the consequence of the complex interplay between solar flare and geomagnetic storm on the magnetosphere-ionosphere (M-I) coupling is a critical aspect to space weather research. This is the first attempt to simulate the concurrent solar flare and geomagnetic storm effects on M-I coupling using the state-of-art geospace model which integrates Lyon-Fedder-Mobarry -Thermosphere-Ionosphere-Electrodynamics General Circulation Model -the Rice Convection ring current Model (LTR) in a self-consistent way. Our results indicate that dayside E-region electron density enhancements peak nearly at the same time as the flare and these electron density enhancements at middle latitudes are not very sensitive to storm forcing. F-region electron densities also have an immediate response to solar flares but take longer to recover compared to E-region ionosphere, and dayside F-region electron density enhancements are more prominent for more stormy conditions. These dayside middle-latitude F-region enhancements intensify tongue of ionization in the polar cap region. Both E- and F-region electron density increases contribute to polar ionosphere conductance enhancements that have both local and global consequences. Flare-induced conductance enhancements tend to reduce the amount of Joule dissipation into upper atmosphere and cross polar cap potential around solar flare peak (12:00 UT), and increase dayside field aligned currents and Joule dissipation afterward (12:20-13:30 UT). These effects are more appreciable for stronger solar wind driving conditions. These simulation results provide important references for interpreting observed solar activity/cycle dependence of magnetosphere-ionosphere coupling phenomena.