Neutral wind effects on the equatorial F-region ionosphere

Abstract

The winds and temperatures calculated by the NCAR thermospheric general circulation model (TGCM) for equinox and solstice conditions are used to investigate their effect on the low-latitude ionospheric F-region. Calculated values of ƒof2 are compared with observed values at two stations, Huancayo, Peru (1°N dip latitude), and Tucman, Argentina (11°S dip latitude). The results show that during the solar cycle maximum equinoctial period good daytime agreement is obtained between calculated and observed ƒoF2 values at Huancayo, Peru, and at Tucuman, Argentina. Night-time agreement at Tucuman is not as good, suggesting that the observed ionospheric behaviour may be responding to dynamics associated with the midnight temperature bulge at low latitudes. The wind calculations by the TGCM consider only in situ thermospheric forcing and the results indicate that upward-propagating tides from the lower atmosphere are important for describing both thermospheric and ionospheric dynamics at low latitudes. During the December solstitial period, agreement between calculated and observed values at both Huancayo and Tucuman is improved when the wind field is included in the calculations. However, it is still necessary to include the dynamics associated with the midnight temperature bulge to obtain good agreement between the calculated and observed values of ƒoF2.