Publication Date:
2017-07-27
Description:
The thermospheric zonal winds measured by the CHAMP satellite are used to statistically determine climatology under quiet and active geomagnetic conditions. By collectively analyzing the bin-averaged wind trend with F 10.7 and the solar-induced difference in wind structures, the solar flux dependence of global thermosphere zonal wind is determined. The increase of solar flux enhances the eastward winds at low latitudes from 18-06 MLT. The increased ion drag reduces the night-time eastward wind in the subauroral latitudes, and the daytime westward winds from 06-08 MLT at all latitudes decrease with increasing solar flux. Zonal winds show coupled seasonal/extreme ultraviolet (EUV) dependency. The equatorial zonal winds from 18-04 MLT indicate weaker eastward winds during the June solstice at high solar flux levels. Quiet-time eastward winds at subauroral latitudes from 16-20 MLT are further decreased in the winter hemisphere. Influenced by asymmetries in solar illumination and the magnetic field, zonal winds show hemispheric asymmetries. Quiet daytime winds are additionally influenced by solar illumination effects, and the westward winds at the middle and subauroral latitudes are always stronger in the summer. The night-time eastward winds are higher in the winter hemisphere during the solstices, as in the southern hemisphere during equinoxes, with the winter-summer asymmetry lessened or receding at the solar maxima. Storm-induced subauroral westward disturbance winds are higher in the summer hemisphere and in the northern hemisphere during equinoxes. At a high level of solar flux, the westward disturbance winds are comparable in the two hemispheres during December solstice. Geomagnetic disturbance wind observations from CHAMP agree well with the empirical geomagnetic disturbance wind model (DWM07), except for stronger subauroral westward jets. Westward winds during the afternoon may be enhanced in the auroral latitudes before the initial time of a storm main phase.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
Permalink