We are currently in the process of adding a forward modeling capability to IDA4D. Our philosophy has been, and remains to stay as simple as is physically plausible. Therefore, we are implementing a forward model of the electron density continuity equation, since it is electron density that IDA4D solves for.
We have currently implemented a forward model transport of the electron density due to ExB drifts at high latitudes and equatorial latitudes. At high latitudes we use the AMIE data assimilation method to get estimates of ExB drifts, and project them along field lines to other altitudes.
At equatorial latitudes, we have implemented a method by which we take daytime equatorial drifts at Jicamarca inferred from ground-based magnetometers using a method developed by Dr. Dave Anderson. These drifts are projected along field lines, providing a progressively larger northward (southward) drift velocity the further away from the equator the field line gets.
An example result is presented below for November 20, 2003. The inferred equatorial drifts for November 20 are given in the figure (red color). The link to the movie provides results from IDA4D for a 2D slice (altitude versus latitude) along the geomagnetic longitude at Jicamarca. The upper panel is the case with the equatorial drifts and the lower panel without. Note that the drifts do not start until a little after 12 UT (7 local time).