Universal time control of the south polarFlayer during the IGY

Abstract

A reexamination of south polar F layer data from the International Geophysical Year has been made, and these results were compared with recent satellite measurements of low-energy electrons. The ionospheric data were plotted so that they would show more clearly the dominance of universal time in the control of polar F layer electron densities. This plot of the data also establishes the clear dependence of polar F layer electron densities on corrected geomagnetic latitude. Comparison between the latitudinal dependence of the F layer electron densities and that of the low-energy electron measurements shows close agreement. This agreement suggests that influxes of low-energy electrons into the ionosphere may be responsible for maintaining or enhancing the south polar F layer. Thus, if universal time control of the F layer is due to precipitation of low-energy electron fluxes, one could say that electron precipitation itself must be dependent on universal time. The latitudinal dependence of south polar F layer electron densities indicates that in winter the area of universal time control is restricted to corrected geomagnetic latitudes greater than 50°. Other workers have indicated that in summer universal time control existed at midlatitudes, but only in the South American sector. Present satellite measurements do not support an intrusion of these low-energy electrons down to midlatitudes. Thus, an unknown process confined to this area in summer appears to be operating.