Neutral-air winds in the ionospheric F-region for an asymmetric global pressure system

Abstract

This is an extension of a previous study by the author, in which a theoretical pattern of neutral-air winds, driven by pressure-gradients and moving ions, in the ionospheric F-region, was derived. Several modifications have been made to the method of analysis, including the use of a more detailed and realistic model of upper-air pressures. The new ‘asymmetric’ pressure model has pressure maximum and minimum, not at diametrically opposed points of the Earth, but at 1400 and 0330 hr LMT so that isobars are more crowded around sunset than around sunrise. As before, an equatorward wind exists at night, but this is much weaker at very low latitudes and is directed more towards the East. Other new features of the resulting wind system are a stronger, and longer lasting, evening eastward wind and a weaker morning westward wind. This results in a greater mean ‘rotation rate’ for the upper atmosphere than previously derived. The predicted angular velocity of the atmosphere at 250 km is about 1.1 times that of the Earth, but the figure for medium and low latitudes is about 1.2, which compares favourably with the result of 1.3 given by satellite orbital data. The theoretical wind pattern agrees well with available observations.