Ionospheric recombination and the polar stratospheric warming

Abstract

On 23 October, 1958 an abrupt increase in noon value of β, the linear coefficient of recombination at the maximum of production of the ionospheric F-layer, occurred at Cape Hallett, Antarctica. This sudden change, which was followed by a generally higher level of β during the summer months, is shown to be distinct from the normal magnetic disturbance effect. The event was simultaneous with the onset of the explosive phase of the polar stratospheric warming in Antarctica and the beginning of the movement of the cold polar vortex off the Antarctic continent. The accumulated evidence supports King's (1963) theory that there is a change in meridional circulation at high atmospheric levels when the polar vortex begins to move and is replaced by a summer-time high pressure system. Gas welling up in this system could increase molecular concentration at F-region levels and this would result in an increase in β, which is a measure of molecular/atomic ratio at these heights. A similar abrupt increase in β, observed between 9 and 12 October, 1957, confirms the conclusions from the 1958 data. A second sharp increase in β on 7 November, 1957 and 26 November, 1958 appears to be associated with the final movement of the polar vortex off Antarctica when the last change in meridional circulation to a stable summer-time pattern probably occurs.