Meridional thermospheric winds over the Antarctic Peninsula longitude sector

Abstract

Diurnal variations of the magnetic meridional component of the thermospheric neutral wind have been derived for Port Stanley (51.7°S;57.8°W), King George Island (62.2°S,58.8°W) and Argentine Islands (65.3°S;64.3°W). A servo-model based algorithm and two semiempirical procedures are used with ionosonde data input. Derived winds correspond to conditions of low geomagnetic activity and both low and high solar activity for months representative of autumn, winter, spring and summer. The shapes of the diurnal variations determined using the three different methods for a given location and month are fairly similar for all three locations and most months. Wind velocities at a given hour, however, may generally differ by 100 m/ s and by up to a few hundred m/s in a few cases. The amplitude of the diurnal variations is larger in winter than summer for all latitudes and at both low and high solar activity, and generally larger at low solar activity. Daily mean winds are poleward in winter and equatorward in summer at low solar activity for all latitudes but are poleward all the year round during high solar activity, and stronger during winter. There is almost no latitudinal dependence of the daily mean winds in summer and autumn, with velocities being less than about 25 m/ s . By contrast, winter daily mean winds change with latitude, particularly during low solar activity. Moreover, there seems to be a latitude at which the mean wind velocity is minimal both at low and high solar activity. A Fourier decomposition of the diurnal variations for all cases shows that all variations can be reproduced using at the most the first three Fourier components. Results are discussed with reference to other published wind determinations for the Antarctic Peninsula area and for the New Zealand longitude sector, and with reference to winds derived using the well-known HWM93 empirical model.