Geophysical Research Letters:  The vertical ion motion in the equatorial ionosphere plays a key role in the space weather. Satellite observations found that such vertical motion during periods with low solar activity can be quite different from the known climatology, and the cause is not clear. Using a whole atmosphere general circulation model, WACCM-X, we are able to reproduce the pattern of the vertical ion motion similar to that observed during low activity solar cycle periods. By analyzing the model results, we find that the relative significance of the different atmosphere tidal wave components and its variation with solar activity contribute to the solar dependence of the vertical ion motion. The propagating altitudes of tide with 12-hour period, as well as where and when the tidal wind becomes large, are of particular importance.

WACCM-X simulation, vertical ExB drift

WACCM-X simulation of monthly averaged vertical ExB drift (a) for June over all local times, and (b) for 0 hour local time over all year under solar minimum conditions.