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

Abstract

[1] 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.Citation: Saunders, A., H. Lewis, and G. Swinerd (2011), Further evidence of long-term thermospheric density change using a new method of satellite ballistic coefficient estimation,

Thermospheric mass density: A review

“…Alternatively, one can calibrate the estimated B values of a collection of objects against density derived from a known object at coincident times and altitudes (e.g., . Discussions of empirical B estimation may be found in Bowman (2002), Cefola et al (2003), Emmert et al (2004Emmert et al ( , 2006, Picone et al (2005), Bowman and Moe (2005), Emmert (2009), Pardini et al (2010, Saunders et al (2011), andSang et al (2013).…”

“…More recently, computationally intensive methods were presented by Cefola et al (2003), Bowman et al (2004), Picone et al (2005), and Saunders et al (2011).…”

“…Orbit-derived estimates of long-term density trends have been prepared by Keating et al (2000), Emmert et al (2004Emmert et al ( , 2008Emmert et al ( , 2011Emmert et al ( , 2015, Marcos et al (2005), and Saunders et al (2011). These studies have been reviewed by Emmert (2015).…”

“…Density data for individual objects have been compiled by Jacchia and Slowey (e.g., 1963,1972,1975, Barlier et al (1978), Bowman (2004), Emmert et al (2004), , Saunders et al (2011), and Dudok de Wit and . Density values are typically associated with perigee altitude, latitude, and local solar time, although King-Hele (1987) showed that an altitude that is ½ scale height above perigee is more appropriate (a scale height is the altitude change corresponding to a reduction of mass density by a factor of 1/e).…”

Climate Change in the Upper Atmosphere

“…Keating et al (2000), Emmert et al (2004Emmert et al ( , 2008, Emmert & Picone (2011), Marcos et al (2005) and Saunders et al (2011) used this technique and confirmed that the thermospheric density at fixed height is indeed decreasing. Observed trend magnitudes range from about -2%/decade to about -6%/decade, and generally increase with altitude.…”