Source and evolution of the ionospheric F-region tongue of ionization and patches

English Abstract:

The high-resolution NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) has been employed to numerically study the source and evolution of the ionospheric F-region tongue of ionization (TOI) and patches, which are electron density enhancements in the polar region with fine structures. The model is run for different interplanetary magnetic field (IMF) conditions. It is found that the formation of TOI and patches is critically dependent on the Universal Time (UT). TOI and patches occur preferentially at the UT when the high latitude ion convection pattern is closer to the daytime high middle latitude ionosphere so more plasma can be transported into the polar region. This UT dependence is different between the northern and southern hemispheres because of the different separations of the magnetic poles from the geographic poles in the two hemispheres. Furthermore, the effect of subauroral polarization streams (SAPS) on the formation of TOI and patches is examined by running the TIEGCM with and without the SAPS in the model.