Latitudinal and Diurnal Variations of Neutral Density forQuiet Geomagnetic Conditions

摘要

An extensive database of CHAMP neutral density measurements during 2001-2005 is used to re-examine latitudinal and diurnal variations of the exosphere temperature. Exosphere temperatures were derived from the measured neutral densities based on the hydrostatic assumption. A linear regression analysis was conducted to model exosphere temperatures during periods of magnetic quiet times. To improve the previous neutral temperature models, we generalize the latitudinal and diurnal dependences of temperature on solar flux. When compared with the Jacchia 1971 model (J71), the new model shows more detailed diurnal variation. Our results indicate that dayside temperatures extend into the evening sector with small gradients until midnight. In the post midnight sector temperature drops sharply to reach a minimum near 02:00 local time and recovers gradually to daytime values near local noon. The results provide an improved understanding of thermosphere responses to solar flux and more accurate specification of thermospheric densities.