Deceleration of the high-latitude thermospheric wind by polar cap gravity waves

This letter explores the hypothesis that gravity wave drag may account for the observed deceleration of the thermospheric anti-sunward wind near the n ightside auroral oval, which at times has been seen to reduce to near zero in a horizontal distance of a few hundred kilometres. Other high-latitude o bservations have revealed thermospheric gravity waves that appear to propag ate across the polar cap from the nightside to the dayside, and hence are m oving counter to the wind near magnetic midnight. Approximate constancy wit h altitude of the vertical velocity amplitudes of these waves suggests a mo derate level of energy dissipation is present. Calculations indicate a wave -mean flow interaction could lead to a deceleration of the wind of magnitud e comparable to that observed.