THERMOSPHERIC NIGHTTIME NEUTRAL TEMPERATURE AND WINDS OVER FRITZ-PEAK-OBSERVATORY - OBSERVED AND CALCULATED SOLAR-CYCLE VARIATION

Nighttime thermospheric winds and temperatures have been measured over Fritz Peak, Colorado (39.9 degrees N, 105.5 degrees W), with a high-r esolution Fabry-Perot spectrometer for nearly 17 years between 1968 an d 1985. We use data for two specific November periods, (1) 1984, near solar cycle minimum, and (2) 1979, near the peak of solar cycle 21, to illustrate the measured solar cycle variation of nighttime neutral ga s temperature and winds over the station. In particular, we present da ta for November 11, 1979, the day following the day when the solar F-1 0.7 radio flux emission reached its greatest daily value of 367 J (1 J = 1.0 x 10(-22) W m(-2) Hz(-1)). The nighttime measurements, all sele cted for geomagnetic quiet conditions, show a considerable variation o f the thermospheric temperature between solar minimum and solar maximu m of nearly 500 K but a relatively minor variation in the thermospheri c winds. The recently developed National Center for Atmospheric Resear ch thermosphere-inosphere-electrodynamics general circulation model (T IE-GCM) is used to simulate the geomagnetic quiet time variation of gl obal thermospheric properties for the two periods and also to perform a time-dependent simulation to calculate the thermospheric variation d uring November 9-12, 1979, when the solar F-10.7 flux varied from 314 J, 367 J, 325 J, and 294 J, respectively The TIE-GCM histories are use d to construct the diurnal variation of thermospheric temperatures and winds as a function of altitude over Fritz Peak Observatory. The aero nomy calculated by the TIE-GCM is also used to predict the diurnal var iation and height of the 630-nm volume emission rate. The station proc essor calculates the emission-weighted height-integrated Doppler line profiles and Doppler shift profiles as would be observed from a ground station. These profiles are reduced into winds and temperatures in a manner similar to the experimental measurements and can be compared wi th the actual observations. The results show that the TIE-GCM calculat ed Doppler temperature and winds are in reasonable agreement with the observations for the two periods representing solar minimum and extrem e maximum conditions, suggesting that the solar flux model and aeronom ic processes in the TIE-GCM can simulate the main thermospheric variat ions throughout the solar cycle. Furthermore, the time-dependent calcu lated variations of Doppler temperature and winds also remain in good agreement with the observations of November 11, 1979, which is the day following the maximum solar EUV perturbation of the Earth's upper atm osphere during the entire solar cycle 21. These results show the need for time-dependent calculations when geophysical parameters have large changes during; the course of the period of simulation. The station p rocessor results indicate that the altitude of the 630-nm emission var ies during the solar cycle by keeping at a near-constant pressure surf ace, whose geometrical height changes with the solar cycle.