A Simulation Study of Ionization Depletion in the Auroral Ionospheric F-Region Caused by Strong Convection Electric Field

The effects of strong convection electric field on the electron density in the auroral ionospheric F region have been simulated numerically by means of a physical model. It is found that an enhancement of electric field directed west northward in post noon or west southward in pre noon results in an ionization depletion with its maximum at altitudes 40 50 km higher than that of the F 2 peak. When the enhanced electric field lasts for 45 min and has a maximum about 32 mV/m, the resulted ionization depletions reach their maximum at the time just ～10 min behind the time when the convection electric field and ion temperature enhancements reach their maximum. This is consistent well with EISCAT observations. The magnitudes of the percentage ionization depletions and their recovery time are dependent not only on the intensity of the electric field, but also on the diurnal variation phase of the background electron density.