Climatology of Thermospheric Temperature and Oxygen Density during 2002-2013 at Millstone Hill

Abstract:

In recent years, climate change has become an area of increasing importance as researchers strive to better understand the impact of increased greenhouse gas concentrations on earth’s atmosphere. Past studies suggest that in the thermosphere and ionosphere, there is a cooling effect which results in a reduction in neutral densities and height dependent changes in electron density. The purpose of this study is to further investigate the long-term changes in the neutral atmosphere by using ground-based incoherent scatter radar (ISR) measurements of the ionosphere and thermosphere. Ion energy balance calculations can be used to estimate exospheric temperature and neutral oxygen density from the radar-measured ionospheric parameters. By using modified versions of existing codes that describe the ion energy balance equations [Nicolls et al., 2006], ionospheric data collected from the Millstone Hill ISR (42.6°N, 288.5°E) between 200 and 600 km from 2002-2013 has been used to calculate exospheric temperature and neutral oxygen density. These results are then used to create a new local empirical model that can describe the climatology of these parameters, varying with local time, season, and solar and geomagnetic activities. Comparing the exospheric temperature and neutral oxygen density data measured at Millstone Hill to corresponding MSIS values, there is a possible long-term cooling trend seen in these observed thermospheric parameters at Millstone Hill. These results, based on the most recent solar cycle observations, will be extended to include more solar cycles, and a much improved understanding of the thermospheric long-term trends may be reached.