Saint-Santin Radar Observations of Lower Thermospheric Storms
Résumé
Incoherent scattare measurements of ion drift velocities obtained by Saint-Santin-Nançay radar have been used to study the lower thremospheric wind disturbances during geomagnetic storms. A storm-time meridional circulation with equatorward wind velocities at higher altitudes (h> 135 km) is revealed. The transition altitude below which the circulation reverses direction is also traceable. The strenght of the circulation is in good agreement with Blanc and Richmond's (1980) model simulation for intense storms. Some evidence is also found for phase variations in the semidiurnal tide during storm periods, but its interpretation is difficult because of the restriction of the data to daytime hours