G2-8


         WEB-BASED EMPIRICAL MODELS OF THE IONOSPHEIEE
         AND THERMOSPHERE USING INCOHERENT SCATTER
         RADAR DATA

         J.M. Holt, S. Zhang
         hlIT Haystack Observatory
         Westford, MA 01886


    Improved specifications and predictions of the
ionosphere/thermosphere (IT) system are an important objective of the
National Space Weather Pro- gram. As a contribution toward meeting this
objective, we have developed several empirical models of the average
behavior and variability of key parameters which characterize the IT
system. These models will be valuable in several ways to space weather
studies and systems. Incoherent scatter radar data are available only a
few days a month due to budgetary restrictions, but the models will
always be available to provide a climatological representation of the
state of the ionosphere and its variability for any set of conditions.
The models covers a wide range of latitudes and altitudes and thus are
useful for validation of global theoretical and empirical models. They
will also be used in investigations of specific scientific problems,
such as storm-time density gradients and enhancements. Preliminary model
results are now available over the World Wide Web
(http://www.openmadrigal.org) for user-specified input parameters.

    The models are based on Millstone Hill incoherent scatter radar data
from 1977 to the present. They include a local model of the E and
F-region ionosphere over Millstone Hill; a regional model of basic and
derived F-region scalar parameters as measured from Millstone Hill,
including electron density, electron and ion temperature; and a model of
the ExB plasma drifts and corresponding electrostatic potentialpatterns.
The scalar models are keyed to solar and geornagnetic indices chosen by
multiple regression, so that deviations of actual data from the model
represent the remaining day-to-day variability due to such causes as
tidal forcings, gravity waves and uncertainties in the solar EUV flux.
The electric field model is keyed to the interplanetary magnetic field.
It represents the average response to solar wind induced changes in the
magnetospheric convection, thus providing a baseline from which more
variable effects of substorms, storms and disturbed neutral winds (the
disturbance dynamo) can be isolated.


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