Last changed in November 2001
Plasma drift/electric field model
The plasma drift/electric field model will provide electrostatic
potential patterns and the corresponding electric fields and ExB
plasma drifts over the apex magnetic latitude range of 50 degrees
through 82 degrees, based on data from the complete Millstone Hill and
Sondrestrom ISR databases.
Line of sight Doppler ion drift measurements are used to determine the
northward and eastward ion drift components as a function of Apex
latitude, local time, and season. The drifts in each of these bins are
then fit to the IMF By and Bz values, using the following relationship
V_North = A + B * (By) + C * (Bz)
V_East = D + E * (By) + F * (Bz)
Where A-F are the fit coefficients, and By and Bz are the 15
minute averages of the IMF. The IMF data is corrected to account for
propagation from the IMP 8 satellite to the ionoshpere.
The plasma drift/electric field model will represent the average
response to the solar wind induced changes in the magnetospheric
convection, thus providing a baseline from which the more variable
effects of substorms and storm, and disturbed neutral wind (the
disturbance dynamo) can be isolated [e.g. Foster et al, 1986].
Millstone Hill lies near the equatorward boundary of most convection
models, so our plasma drift model, which will include data near and to
the south of Millstone, will help specifiy the low-latitude boundary
of the magnetospheric convection pattern which is not well represented
at present.
Model Status
The preliminary work of binning the data and computing the fit
parameters has been completed. Examiniation of the fit parameters for
each bin, as well as any necessary smoothing of the parameters between
local time and latitude bins remains to be done. For that reason,
results from out electric field model are currently unavailable. We
have made two movies of the model output, which you can click on
below, which show convection changes as one component of the IMF
changes. It is evident from these movies that there are some bins for which some tweaking of the parameters is necessary.
There are still a number of modifications which need to be made to the model:
- Utilize IMF data from other solar wind monitors (Wind, ACE, etc.)
- Parameterize the model by polar cap index and/or hemispheric power index
- Include observations from the Sondrestrom Incoherent Scatter Radar
- Compute polar cap potential patterns based on velocity measurements
Animated Gifs of selected Model output
References