F-Region Dynamo Simulations at Low and Mid-Latitude

The “ F -layer dynamo” or “ F -region dynamo” concept was introduced by Rishbeth (Planet. Space Sci. 19(2):263–267, 1971a ; 19(3):357–369, 1971b ). F -region winds blow the plasma across magnetic field lines setting up transverse drifts and polarization electric fields leading to equatorial downward current during the daytime and upward current at dusk which were confirmed by satellite observations. In the daytime the F -region current can close through the highly conducting E -region. At night when the E -region conductivity is small the F -region dynamo generates polarization electric fields and is mainly responsible for the nighttime drift variations. In the evening the F -region dynamo is instrumental in generating an enhanced vertical drift, the pre-reversal enhancement. The current due to the F -region dynamo is larger at day than at night, but the F -region dynamo contributes approximately 10–15 % to the total current at day versus approximately 50 % at night (Rishbeth in J. Atmos. Sol.-Terr. Phys. 43(56):387–392, 1981 ). The F -region dynamo effects strongly depend on the Pedersen conductivity and therefore on the solar cycle. We will review the influence of the F -region dynamo on the ionosphere in general and particularly focus on the role it plays in generating ionospheric currents and magnetic perturbations at low-earth orbiting (LEO) satellite altitudes.