Ionospheric Dynamo Currents and Magnetic Perturbations Modeled in a Realistic Geomagnetic Field

The National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General-Circulation Model (TIEGCM) is used to study the spatial and universal-time variations of electric currents generated by the ionospheric wind dynamo, and their associated geomagnetic perturbations. The model results will be compared with observations of quiet-day electric fields and magnetic perturbations as well as with previous model results. Significant longitudinal variations of the currents are created by longitudinal variations of the geomagnetic field, associated with both the dipole tilt and the non-dipolar distortions of the geomagnetic field. In particular, the geomagnetic-field distortion in the Atlantic sector creates much stronger equinoctial field-aligned currents between the northern and southern hemisphere than at other longitudes. These currents make a significant contribution to geomagnetic perturbations both below and above the ionosphere.