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.
References