Variations of total electron content during geomagnetic disturbances: A model/observation comparison

This paper studies the ionospheric response to the major geomagnetic storm of October 18-19, 1995, using the NCAR TIE-GCM simulations and the global ionospheric maps (GIM) of total electron content (TEC) observations from the worldwide network of Global Positioning System (GPS) receivers. The TIE-GCM results show a good agreement with the GPS-GIM in terms of simulating storm-time TEC disturbances over the polar regions. The model indicates that the increase of electron density in the high-latitude E and lower F regions below 200 km is directly related to the magnetospheric energy input through auroral precipitation to the ionosphere, while the decrease of TEC is mainly due to the increase in O₂ and N₂ densities in the upper F region above 200 km. During the recovery phase, both the TIE-GCM and GPS-GIM reveal a distinct hemispheric asymmetry in the TEC integrated above |50°| magnetic latitude, with a 20% decrease in the southern (summer-like) hemisphere and a 30% increase in the northern (winter-like) hemisphere.