Formation of maximum electric potential at the geomagnetic equator by the disturbance dynamo

The effect of a disturbance dynamo during geomagnetic activity on the equatorial ionospheric electric fields is investigated, using model results from the NACR/TIEGCM (National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model). Model runs are made for different time-lengths of geomagnetic activity, for different seasons, and for different solar activities to investigate how and where the maximum electric potential forms. Model results show that the maximum electric potential is located at around 300 km altitude and at local time after the pre-reversal enhancement at equinox for high solar activity. For the case at solstice, without pre-reversal enhancement, the location moves to around 110 km altitude and to the local time close to midnight. Giving various parameters in the model runs to simulate different background conditions, many important output quantities are used to study the distributions of perturbed electric potential at the geomagnetic equator. Model investigation indicates that normal quiet time electrodynamics, at different seasons with different solar activities, significantly affect the distribution of perturbed current density associated with geomagnetic activity. Furthermore, model results also reveal that significant perturbed zonal electric fields tend to build up six hours after the onset of geomagnetic activity, except at regions close to sunset and sunrise, and the perturbed vertical electric fields increase with the time length of geomagnetic activity.