Mathematical Simulation of the Atmospheric Electric Field Disturbance during a Geomagnetic Storm on 17 March 2015

It follows from the observational data that variations of the atmospheric electric field occur during geomagnetic storms. In this paper, we present the simulation results of ionospheric electric fields during the main phase of the geomagnetic storm on March 17, 2015, within the framework of a quasi-stationary model of a conductor consisting of the atmosphere and the ionosphere. For this purpose, the satellite data on the global distribution of currents between the magnetosphere and the ionosphere are used to describe the magnetospheric source of the electric field. A variation of the electric potential in the ionosphere leads to a variation of the electric field in the entire atmosphere, including its surface layer. It is important that during a geomagnetic storm, the observatory in which the atmospheric electric field is measured significantly changes its position relative to the direction of the Sun. This leads to significant changes in the ionospheric conductivity above the observatory, which affects both the ionospheric electric field and the atmospheric part of the global electrical circuit (GEC). Therefore, when assessing the effect of a geomagnetic storm on the atmospheric electric field in a particular observatory, it is necessary to take into account the local time when comparing the measurement data with the geomagnetic activity indices. For the storm on March 17–18, 2015, we found that taking into account the variations of the ionospheric electric field when calculating the atmospheric electric field allowed us to reproduce the disturbances of the fair weather electric field observed at the Borok Geophysical Observatory. Based on the simulation results, it is shown that during extremely strong magnetic storms, additional atmospheric electric field variations in some places on the Earth have the same scale as the fair-weather field itself.