The FTS instrument on SciSat-I observed over 1 ppmv NOx in the lower polar mesosphere, in mid February of 2004, more than 100 times normal. Using a middle atmosphere GCM we investigate whether solar proton events or subsequent associated aurorae can explain the NOx observations. We find that the solar proton events produce insufficient amounts of NOx, less than 2 ppmv at 90 km. However, it is likely that intense aurorae associated with the Oct.--Nov. 2003 solar storms, and their aftermath, produced thermospheric values of NOx reaching hundreds of ppmv. In addition, from our simulations we infer that NOx rich air must have experienced unusually confined polar night descent in the mesosphere in December and January.