The High-Latitude F-region Irregularity Structure During the October 30–November 4, 1968, Magnetic Storm


  • Jules Aarons


A study of multi-station scintillation observations of the 137-MHz transmissions from ATS-3 during the magnetic storm of October 30 to November 4, 1968, was made to separate the diurnal pattern of high-latitude irregularities from storm-time effects. The night maximum was maintained during magnetic storms, but the pattern was modulated by storm-time effects. Daytime scintillation indices were increased at specific times during the magnetic storm; a universal time correlation was observed for stations in Europe and in North America. Peak scintillation activity shifted from before midnight (under quiet magnetic conditions) to the 0130 to 0430 time period. A sharp boundary of less than 2° was noted between scintillating and non-scintillating regions. 40-MHz transmissions from Explorer 22 during one period of the storm verified that the irregularity structure extended from 48° to 50° GN to auroral latitudes. Using records of 54-MHz transmissions from Transit 4A taken between 1962 and 1965, as well as the ATS-3 data, it was found that during magnetic storms the lower edge of the scintillation boundary, which bounds the irregularity structure, moves below its quiet positions to lower latitudes, particularly in the midnight-to-dawn time period. It was found that the observations were more adequately ordered by invariant latitudes than geomagnetic (dipole) latitudes used in scintillation papers. Latitude variations in position of the boundary are compared with the trough. It is found that the irregularity-boundary changes as a function of K index and as a function of local time. Latitude variations in the position of the boundary are compared with the trough. Akasofu's concept of nearly open field lines in the plasmapause during magnetic storms might account for the increased scintillation indices as well as for the lower position of the scintillation boundary during magnetic storms.