Rotation of the Variation of Upper Atmosphere

Abstract

FROM observations of satellite orbits it has been deduced that the atmosphere above about 200 km altitude rotates 20–30% faster than the Earth, so that there exists a net west-to-east wind of order 100 m s⁻¹ (refs. 1, 2). This “super-rotation” has not yet been satisfactorily explained. The wind systems driven by the diurnal heating and cooling of the thermosphere³ do not produce any significant net rotation at mid-latitudes⁴. The satellite data are somewhat weighted towards low latitudes so the rotation may be most pronounced there; calculations suggest that the thermospheric winds may produce some net rotation at low latitudes⁵, though probably not enough to account fully for the observations. Ionospheric motions driven by dynamo electric fields in the E region do not seem to make any significant difference to this result⁵.