Ionospheric Climatology Over Millstone Hill

Zhang, S.-R., and J. M. Holt,

MIT Haystack Observatory, Route 40, Westford, MA 01886 United States

26 years of incoherent scatter observations over Millstone Hill since 1976
have been analyzed and modeled in order to study the climatological
behavior in the local ionosphere-thermosphere system. A bin-fit technique
is applied to process and represent the huge volume of data: measurements
are binned according to local time, season, and altitude; sorted data in
each bin are fitted into an empirical model where solar activity index
F107 and geomagnetical activity index Ap are included as keyed inputs
[Holt et al., 2002]. This paper focuses on seasonal, semiannual and annual
variations and the long-term trend in electron density, electron
temperature and ion temperature measurements over a 200-500 km height
range of the F2 layer. A clear semiannual variation of the electron
density is seen above the F2 peak during the day, as well as at the F2
peak and below during the later afternoon to evening period (16-20LT) .  
The semiannual variation of the electron temperature persists with minimum
at equinox during the night, while the annual variation prevails by day
with maximum in summer.