The performance of the Dibrugarh University low latitude 3D theoretical model at different geomagnetic activity levels and for intense geomagnetic storms has been investigated. In this model the continuity, momentum and energy balance equations of ion and electron flux along geomagnetic field lines from the Northern to the Southern hemisphere are solved simultaneously. The model is used to simulate electron density at different geomagnetic activity conditions Ap=5, 10, 20. With the increase of the geomagnetic activity, the Equatorial Ionization Anomaly (EIA) exhibits a tendency to come closure towards low latitudes and the EIA merges at Ap=20. The effect of two intense geomagnetic storms that occurred in July & November 2004 on Total Electron Content (TEC) has been investigated and compared with observed TEC data. Agreement between model and measured data was found to be very good.
