Magnetospheric—ionospheric effect on the ground-level atmospheric electric field at Helsinki

Abstract The magnetospheric—ionospheric influence on the ground-level atmospheric electric field measured at Helsinki is investigated on the basis of comparison with a numerical model of the high-latitude ionospheric electric field of solar wind of magnetospheric origin. It is found that the contribution of the magnetospheric-ionospheric generator to the ground-level atmospheric electric field varies with the local time, the season and the conditions of the magnetosphere, and the large-scale electrodynamic features of the ionosphere. The latter are characterized as disturbances in the east and north components of the interplanetary magnetic field. The atmospheric electric field values can differ in winter by 100–150 Vm −1 between extremely quiet and extremely disturbed magnetospheric conditions.