A Statistical Model of the Electric Field and F-Region field-aligned
Ion Drift over Millstone Hill

John M. Holt and Shun-Rong Zhang
MIT Haystack Observatory, Route 40, Westford, MA 01886

Abstract

All Millstone Hill incoherent scatter radar data collected since 1978 are
available through the Madrigal Database at MIT Haystack Observatory.  A
set of empirical models for basic and derived incoherent scatter
parameters, including electron density Ne, electron and ion temperatures
Te and Ti, electric field and parallel ion drift is being developed from
this extensive dataset. Such models of the average behavior of key
ionosphere-thermosphere (IT) parameters, based on long term accumulated
data, are important for space weather studies not only in terms of
quantitative descriptions of the IT system but also in terms of clarifying
several outstanding scientific problems.

This paper presents statistical models of the local electric field and
geomagnetic-field-aligned ion drift in the ionospheric F-layer.  All local
(radar elevation > 45 degrees) ion line-of sight measurements are sorted
into bins. The binning parameters are local time (0000-2400 LT), and day
of year (season).  Each data point has a corresponding solar flux index
F107 and geomagnetic activity index Ap. A least-squares fit to all the
data in each bin is computed to determine the electric field as a function
of Ap and the field-aligned drift as a function of F107 and Ap.  Unlike
previous Millstone Hill local electric field models, the components of the
drift are determined in a statistical sense rather than by first computing
the parallel and perpendicular drift components from triplets of
line-of-sight measurements. We will present the data distribution in each
bin and discuss the main features of the results.