Empirical Model of Lower Thermospheric Density for Low Solar Flux and Quiet Geomagnetic Conditions

Abstract

An extensive atmospheric density data base has been developed for the altitude region 140-250 km. The data were obtained with accelerometers on the four low altitude satellites Atmosphere Explorer -C, -D and -E, and S3-1. Measurements obtained over a low solar flux period, January 1974 to November 1976, provide coverage over all latitudes and several cycles of local time variation. Data from over 2000 orbits occurring during geomagnetically quiet days (ap ≤ 15) are analyzed using least-squares multiple linear regression. The resulting empirical model gives neutral density as a function of altitude, solar flux, geomagnetic activity (up to ap ≤ 15), day of year, season and local time. The results are compared with the MSIS and Jacchia 1971 and 1977 models.