An investigation into the influence of tidal forcing on F region equatorial vertical ion drift using a global ionosphere-thermosphere model with coupled electrodynamics

A recent development of the coupled thermosphere-ionosphere-plasmasphere mo del (CTIP) has been the inclusion of the electrodynamic coupling between th e equatorial ionosphere and thermosphere. The vertical ion drifts which res ult are shown to be largely in agreement with empirical data, on the basis of measurements made at the Jicamarca radar and other equatorial sites [Sch erliess and Fejer, 1999]. Of particular importance, the CTIP model clearly reproduces the "prereversal enhancement" in vertical ion drift, a key featu re of the observational data. Inacurracies in the modeled daytime upward io n motion have been investigated with regard to changing the magnitude and p hase of components of the lower thermospheric tidal forcing. The results sh ow that daytime vertical ion motion is highly dependent upon both the magni tude and phase of the semidiurnal tidal component. In addition, the CTIP mo del shows the prereversal enhancement. to be unaffected by changes in tidal forcing, but only for conditions of high solar activity. During periods of low solar activity the form of the prereversal enhancement is clearly depe ndant upon the magnitude and phase of the semidiurnal tide.