It follows from the observational data that during geomagnetic storms, variations of the atmospheric electric field occur. We developed a quasi-stationary model of the coupled ionosphere—atmosphere conductor to calculate the near-Earth electric fields driven by magnetospheric field-aligned currents. To describe the realistic magnetospheric electric generator, data from the AMPERE satellites on the global distribution of the field-aligned currents, have been used. The conductivity tensor of the ionospheric plasma is gyrotropic. We use the height profile of the scalar conductivity in the atmosphere below 50 km that is some average of known empirical models. In E- and F-layers the gyrotropic conductivity tensor of the ionospheric plasma has been constructed on the basis of the empirical models IRI-2016, MSIS 1990 E, and IGRF. In the rest layer 50–90 km we obtain components of conductivity tensor by interpolation. Because in the ionosphere the field-aligned conductivity is a few orders of magnitude larger than the transverse conductivities, a two-dimensional model can be used for the ionospheric part of the conductor. To include the auroral electron precipitation the Weimer model of the additional Pedersen and Hall conductances in the auroral zone has been used. As a result of the numerical solution of the problem, the global distributions of the electric potential are obtained for each moment of time. Variation of the electric potential in the ionosphere cause variations of the electric field throughout the atmosphere, including its near-surface layer. The results of simulations are compared with the observed disturbances of the fair-weather electric field for the strong storm on March 17–18, 2015.