Auroral and sub-auroral F-layer irregularity studies in the Northern and Southern Hemisphere during the equinox transition study September 16-26, 1984

A preliminary model detailing the auroral and sub-auroral nightly behavior of F-layer irregularities during the injection and recovery phases of magnetic storms is outlined. Initially the irregularities spread equatorwards from the auroral region. On subsequent nights in those storms where Dst slowly returns to its zero level there is activity at auroral latitudes at the end of the magnetic storm and finally, relatively high irregularity intensity primarily at sub-auroral latitudes. The model was tested with observations of the irregularities observed during the September 1984 Equinox Transition Study. Observations of irregularities and incoherent scatter were examined for the injection phase of the magnetic storm of Sep. 22 to 23. The concept was to determine what parameters are most important in indicating whether irregularities are present over a range of latitudes from 53 to 78 degrees CGL. The data set indicates distinct correlation with convection velocities in the early portion of the storm when a sub-storm was shown on magnetograms. In the latter half of the night with the magnetic storm fully developed, the data show good correlation with an electron density trough, high electron temperatures, and high velocities. For the recovery phase of a magnetic storm another period in the ETS is examined with sub-auroral irregularities observed during the recovery of Dst when quiet magnetic conditions prevailed. The general form of the model appears to be valid but many aspects of the timing and the magnitude of the irregularity intensity are to be determined.