Ionospheric Es in the Southern Hemisphere Temperate Zone. I. Seasonal Characteristics of f0 Es

Abstract

Detailed seasonal variations of fo Es occurrence are presented for the Southern Hemisphere Temperate zone from the analysis of approximately twenty years of ionosonde data for ten stations (9"·4 to 52"·6 geographic latitude) in the Australasian region. Significant short term features are found: a late autumn enhancement strongest at about 20"S and evidence of a secondary summertime peak one month before the solstice. A comparison between the gross seasonal characteristics of fo Es occurrence with those expected from a simple model of the wind shear mechanism shows similar latitude trends, though the model predicts autumn equinox values which are too low.