Long-Term Thermospheric Trends Based on Satellite Drag Analysis
Abstract
A new database of thermospheric densities has been derived for the period 1970 - 2000 from satellite orbital decay analysis. The data are generated from actual radar tracking observations, rather than from the less accurate historical element sets, to form precise orbit and drag/density data with improved accuracy and one-day resolution. Satellites with high eccentricities were used to achieve long lifetimes and relatively localized latitude and local time resolution. Data are compared to three empirical models (Jacchia, NRLMSIS and NASA MET). The data were normalized to remove systematic model errors vs solar activity detected in all three models. A linear regression through the normalized data was obtained for each satellite. The weighted average of these fits show, at 400 km altitude, a downward trend of about 5% over 30 years with a 95% confidence interval of about 25%. The data are also analyzed as a function of altitude, solar flux and geomagnetic activity, and compared to theoretical predictions. Assuming a linear fit, these results tend to agree with other recent studies indicating a long-term cooling trend in the thermosphere.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMSA53A..04M
- Keywords:
-
- 0350 Pressure;
- density;
- and temperature;
- 0355 Thermosphere: composition and chemistry;
- 0358 Thermosphere: energy deposition;
- 1600 GLOBAL CHANGE