Your descriptions of "explosion-like" burst would match the HAARP experiments and also the orbital release of charged particles, but not the re-entry of a vehicle (no "sparks" as the pieces break apart). The drift rate you mention still makes me think more about the orbital experiment, rather than HAARP. However, it is possible that on that day, HAARP used that drift rate.
Meanwhile, I searched in older journal and found that they were already doing experiments with rockets in 1969: they sent them high enough above the denser parts of the atmosphere, then emitted streams of free electrons in a direction parallel to the local lines of force.
"Artificial aurora experiment: Experiment and principal results" by Hess, W. N., M. C. Trichel, T. N. Davis, W. C. Beggs, G. E. Kraft,E. Strasinopoulos, and E. J. R. Maier
Journal of Geophysical Research, vol. 76, page 6067, 1971.
Obviously, this one is not the one you saw (the 1971 paper was about the experiment done in 1969).
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Going through papers on "Artificial aurora experiments" conducted between 2004 and 2006, I find that they were using a combination of rockets (sub-orbital flights) releasing plasma and/or electron beams, some satellites (same kinds of release) and radio emissions depositing energy in the ionosphere. Some of the experiments were combined (simultaneous use of radio + either rocket or satellite).
There were many (a handful) in that time period. However, I have not yet found one that matches your dates. I still think that what you saw is the "rocket or satellite" contribution... but I am not willing to bet my next paycheck on that.