On the day and night reversal in NmF2 North-South asymmetry

Abstract

A time varying solution of the full continuity equation for electrons in the F2-region is obtained. The effects of production, loss, diffusion and electrodynamic E × B drift are taken into account. In addition, the effects of a transequatorial neutral wind are included. It is shown that a constant North-South neutral wind can produce distributions similar to the day and night-time asymmetrical distributions actually observed in the F2-region. The results show that during day-time ionization is transported from one hemisphere to the other in the direction of the wind. The peak in NmF2 on the southern side is greater than the peak on the northern side during the day, and the peaks achieve their maximum values between 16 and 17 hr LT at magnetic latitudes 15.5°S and 15°N respectively. After 17 hr, the peaks start to decrease, on both sides of the magnetic equator, the southern peak decreasing at a faster rate than the northern peak, until they are equal at about 15° latitude at 20.5 hr; afterwards an asymmetry occurs in the opposite sense until sunrise. These results are compared with observations and suggest the presence of winds blowing from one hemisphere to the other across the magnetic equator.