Further evidence of long-term thermospheric density change using a new method of satellite ballistic coefficient estimation

Abstract

Building on work from previous studies a strong case is presented for the existence of a long-term density decline in the thermosphere. Using a specially developed orbital propagator to predict satellite orbit evolution, combined with a new and accurate method of determining satellite ballistic coefficients, a long-term thermospheric density change has been detected using a different method compared to previous studies. Over a 40-year period between the years 1970 and 2010, thermospheric density has appeared to reduce by a few percent per decade. However, the results do not show the thermospheric density reduction to vary linearly with time. Therefore, by analyzing the derived density data over varying solar activity levels, as well as performing a Fourier spectral analysis to highlight any periodicities, connections with physical phenomena, where possible, are proposed. Copyright 2011 by the American Geophysical Union.