Neutral wind influence on the electrodynamic coupling between the ionosphere and the magnetosphere

Abstract

The influence of the ionospheric wind dynamo on the steady state electrodynamic interaction between the ionosphere and the inner magnetosphere is evaluated with the Magnetosphere‐Thermosphere‐Ionosphere Electrodynamics General Circulation Model (MTIE‐GCM) of Peymirat et al. [1998]. Two types of interaction between the solar wind–magnetosphere (SWM) dynamo and the ionospheric dynamo are considered: either the SWM dynamo is a voltage generator imposing a fixed electric potential in the polar cap or it is a hybrid current/voltage generator such that the electric potential in the polar cap results from the combined action of the SWM and ionospheric dynamos. The following results are found. (1) The dynamo effect of winds that are accelerated by the high‐latitude ion convection increases the meridional electric field in the auroral zone but reduces the potential variation around the Auroral Zone Equatorial boundary (AZEQ) and the plasma pressure in the nightside magnetosphere close to the Earth, corresponding to an enhancement of the shielding effect produced by Region 2 field‐aligned currents. The magnitudes of the wind‐induced effects are on the order of 10% for the shielding potential and 20% for the plasma pressure reduction. (2) The wind‐induced reduction of magnetospheric plasma pressure near the Earth is ∼4 times larger for a doubling of the plasma source density in the tail. (3) The relative influence of winds on shielding is similar for polar cap potential drops of 30 kV and 70 kV. (4) When the wind is allowed to influence the polar cap potential, it increases the potential drop along the polar cap boundary by ∼10% but does not modify the net influence on the shielding potential along AZEQ. (5) The influence of the neutral winds set up by the high‐latitude convection is restricted to the auroral zone.