GEOMAGNETIC INFLUENCES UPON TIDES - WINDS FROM MLT RADARS

The influence of geomagnetic storms on the wind field of the mesosphere and lower thermosphere was investigated by means of ground-based observations with two MF radars, four meteor radars and two LF wind profilers in middle and high latitudes of the northern hemisphere. As the wind field in the height range between about 70 and 110 km is markedly controlled by internal atmospheric processes (e.g. stratospheric warming events, seasonal transitions, atmospheric waves), the individual geomagnetic effects were often masked by such atmospheric variations. Superposed-epoch analyses demonstrate that there were enhanced westward directed winds at middle latitudes and an eastward directed component at higher latitudes (Saskatoon, Canada), whereas the effects in the meridional component as well as in the amplitudes of the tidal waves were markedly smaller.