Day-to-day variations of migrating semidiurnal tide in the mesosphere and thermosphere

By using a general circulation model, we examine behavior of the migrating semidiurnal tide for solar cycle moderate and geomagnetically quiet conditions. We investigate day-to-day variabilities of the migrating semidiurnal tide in the mesosphere and thermosphere and their relation with the migrating semidiurnal tide generated in the lower atmosphere. The results show that day-to-day variations of the migrating semidiurnal tide are evident from the tropopause to the thermosphere. Fluctuations of the migrating semidiurnal amplitude with periods of 10-12 and 25 days are found at altitudes from 20 to 250 km, indicating dynamical coupling between the mesosphere and thermosphere and the lower atmosphere.