Last changed in December 2001 by LPG

Millstone Hill Low Thermosphere Temperature Model

Data obtained from the Millstone Hill incoherent scatter radar (42.6N, 71.5W) during the interval 1987 through 2000 have been analyzed to obtain an experimental model of neutral temperature in the lower thermosphere. The database used in this study covers over 180 days, and spans the altitude range from 105 to 140 km.

The presented model is an extension of Millstone Hill Ionospheric Plasma Model and utilizes the same approach and binning techniques. Local measurements of ion temperature (assumed to be equal to neutral temperature at 105-140 km) are binned in 1 hour local time and 5 km altitude. In each bin, the dependencies on solar and magnetic activity are determined through a least squares fit to the following equation:
    Tn = A + B * F10.7 + C * Ap + D * Ap*F10.7
where Tn is neutral temperature, A-D are the fit coefficients, F10.7 is the previous day's F10.7 index, and Ap is the Ap index for the previous 3 hours. The experiments were assigned to 4 different seasons as follows:

winter 45 > daynumber < 299 spring 45 < daynumber <= 115 summer 115 < daynumber < 229 autumn 229 <= daynumber <= 299,
which leads to relative scarsity of data in spring and autumn. Furthermore, autumn season has the smallest number of data due to lack of experiments. Only day-time data are available at these altitudes due to low signal-to-noice ratio at night. Currently model limits the local time coverage for a particular season based on number of points in the bin and quality of the fit for the bin. Approximately 12 hours of data are available at summer time and 8 hours in winter.