Ion‐neutral momentum coupling near discrete high‐latitude ionospheric features

We have developed a two-dimensional numerical model to study the momentum coupling between the ionosphere and neutral atmosphere in the vicinity of discrete high-latitude features, such as convection channels and plasma density troughs. The model, which is based on generalized magnetohydrodynamic equations, takes account of global pressure gradients, viscous dissipation, ion drag, the Coriolis force, and electrodynamic drifts. From our initial steady state investigation, we have found the following: (1) in convection channels, significant shears and rotations of the thermospheric flow can occur below 200 km if a minimum in the electron density profile is present between the E and F regions; (2) in convection channels, the thermospheric wind decreases with height in the F region owing to the effects of horizontal viscosity; (3) at low altitudes, the boundaries of convection channels may produce Ekman spirals; (4) a convection channel acts to induce a thermospheric motion over a region that extends up to 1000 km on both sides of the convection channel owing to the effects of horizontal viscosity; (5) in general, thermospheric winds driven by large-scale pressure gradients have an appreciable effect on the thermospheric flow in and near convection channels; (6) narrow channels of rapidly convecting, low density plasma produce a small thermospheric response; and (7) Joule heating is generally the dominant heat source inside convection channels, while viscous heating dominates outside. Frequently, however, viscous heating can be the dominant heat source both inside and outside of convection channels.