Theoretical study of the ionospheric dynamo region inside the South Atlantic Anomaly

The South Atlantic Anomaly (SAA) is a region where the geomagnetic field is significantly lower than that of the surrounding area. On the basis of the models of CHAOS-7.8, Mass Spectrometer Incoherent Scatter Model (NRLMSISE-00), and International Reference Ionosphere 2016 (IRI-2016), we theoretically investigated the lower and upper boundaries of the ionospheric dynamo region inside the SAA. In the ionospheric dynamo region, electrons are coupled with magnetic field lines, whereas ions are decoupled from magnetic field lines. Our results showed that the ionospheric dynamo region inside the SAA is higher and larger than that outside the SAA. We also studied the boundary variations of the dynamo region inside the SAA depending on the seasons and solar activities. We found that the dynamo region inside the SAA is the highest and largest in the summer of the southern hemisphere at solar maximum. The larger and higher altitude range of the ionospheric dynamo region in the SAA can contribute to the stronger ionospheric currents in this region.