Thermospheric temperatures and meridional winds measured at Albany, New York during geomagnetically disturbed periods

Abstract

High quality optical data, obtained by using a high-resolution Fabry-Perot interferometer, were used to derive the thermospheric neutral temperatures and meridional wind velocities at a mid-latitude station, Albany (42.7°N, 73.8°W), New York, during the period 1978–1982. A total of 24 geomagnetically active nights, when the K p index was more than 3, were selected during the observation period. The neutral temperatures varied between about 900 and 1600 K, with a mean value of 1276 ± 54 K. Thermospheric temperatures were also estimated for these selected nights, using the 83 and 86 versions of the MSIS thermospheric model to compare with the experimental values. The experimentally determined temperature variations at the F-region heights were found to be in qualitative accord with the predicted variations based on the thermospheric models. However, the MSIS-83 model gave temperatures smaller than the measured values by about 250 K, while the difference was less than 200 K with the MSIS-86 estimates. In summary, the results of this study show a fair agreement between the observed temperature variations and the estimated variations using the MSIS models for geomagnetically active periods, and there is an increasing need to resolve the quantitative differences. The meridional wind velocities are generally equatorward and they increase from about 125 m s −1 shortly after sunset, to a maximum value of around 200 m s −1 before local midnight, and then decrease to less than about 100 m s −1 toward the early morning hours and become poleward by morning twilight. The mean meridional wind is essentially equatorward in agreement with the thermospheric circulation theory and also in general accord with other mid-latitude optical wind observations.