The effect of non-migrating tides on thermospheric zonal wind and its relation to E and F region electrodynamics
Abstract
The effect of non-migrating tidal waves has recently been identified in many atmospheric and ionospheric parameters. Here we focus on the diurnal, eastward propagating wavenumber 3, DE3, mode. The satellite CHAMP with its sensitive accelerometer on board provides the opportunity to investigate the thermospheric dynamics in great detail. On its near-polar, low- Earth orbit (about 400 km) it is well suited to map the air density and winds along the track. In this talk we concentrate on the equatorial region. Special attention is paid to longitudinal variations of the thermospheric zonal wind. During certain seasons and local times a clear wave-4 longitudinal pattern is evident in the wind speed. From the phase change of this wave over an LT day this pattern can be related to the DE3 tidal mode. So far it has been assumed that the non-migrating wave signal is dissipating at heights above 120 km. Therefore it is still not clear how thewave-4 pattern is coupled into the upper thermospheric zonal wind. At E-layer altitudes the DE3 tides cause modulations of the electric field. These modulations are well recognisable in the longitudinal variations of the equatorial electrojet (EEJ). Highresolution CHAMP magnetic field recordings have been used to investigate the EEJ variations on a statistical basis. From them the response of the E-layer to DE3 tides could clearly be identified. We are going to compare the phase relation and the annual amplitude variation of the current signals at 110 km and the winds at 400 km altitude. From the results suggestions for the coupling mechanisms are deduced.
- Publication:
-
37th COSPAR Scientific Assembly
- Pub Date:
- 2008
- Bibcode:
- 2008cosp...37.1839L