Thermospheric winds from the satellite electrostatic triaxial accelerometer system

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Abstract
A new thermospheric wind measurement technique is reported, which is based on a satellite electrostatic triaxial accelerometer (SETA) system capable of accurately measuring accelerations in the satellite's in‐track, cross‐track, and radial directions. Cross‐track winds measured on 74 orbits between 170 and 210 km during a 5‐day period of mostly high geomagnetic activity are analyzed to demonstrate the potential contributions of SETA data to studies of thermospheric dynamics. On the basis of an analysis which depends upon alignment of null points in the cross‐track winds, the data are shown to be consistent with a two‐cell polar circulation pattern characterized by a main flow parallel to the 1600/0400 geomagnetic local time meridian and return flows in the late morning and late evening sectors. The flow pattern is asymmetric in that it is displaced about 5°–10° latitude toward the noon (geomagnetic local time) sector, and the evening cell is somewhat more diffuse than the morning cell. The system also covers a greater area of the polar cap and is more intense during active (Kp ≳ 5o) than quiet (Kp ≲ 3o) geomagnetic conditions. Average main flow velocities are characteristically of the order of 150±75 m s−1 for Kp ≈ 2o and 375±100 m s−1 for Kp ≈ 5o, the stated variabilities representing 1σ deviations.