Field‐aligned currents in the magnetospheric boundary layer

A self‐consistent magnetopause‐boundary layer model is constructed which contains two current layers, one for the magnetopause and one for the magnetosphere‐boundary layer transition region. Field‐aligned sheet currents in the boundary layer are generated by the plasma flow along the boundary layer. The magnitude of these boundary layer field‐aligned currents is about 10−8 A/m², which can be scaled along field lines to about 5 × 10−6 A/m² near the ionosphere and therefore can be identified as a possible source for the auroral sheet currents. The cross‐field current density in the model is also about 10−8 A/m², which is sufficient to excite the lower‐hybrid‐drift waves to produce the observed electromagnetic fluctuations in the magnetopause‐boundary layer region.