Climatology of globally averaged thermospheric mass density

Abstract

We present a climatological analysis of daily globally averaged density data, derived from orbit data and covering the years 1967–2007, along with an empirical Global Average Mass Density Model (GAMDM) that encapsulates the 1986–2007 data. The model represents density as a function of the F10.7 solar radio flux index, the day of year, and the Kp geomagnetic activity index. We discuss in detail the dependence of the data on each of the input variables, and demonstrate that all of the terms in the model represent consistent variations in both the 1986–2007 data (on which the model is based) and the independent 1967–1985 data. We also analyze the uncertainty in the results, and quantify how the variance in the data is apportioned among the model terms. We investigate the annual and semiannual variations of the data and quantify the amplitude, height dependence, solar cycle dependence, and interannual variability of these oscillatory modes. The auxiliary material includes Fortran 90 code for evaluating GAMDM.