F-region enhancements in the Antarctic

Daily and seasonal variations of the monthly median F2-region critical frequency (ƒoF2) in the Antarctic are examined. The abnormally large increase in ƒoF2 is found to be most distinctive in winter in the areas around Ellsworth, South Pole, Byrd, Little America, Cape Hallett, and Terre Adelie. Statistically, the increase occurs between 0400 and 0900 universal time, although individual days may differ. Synoptic maps of ƒoF2 indicate that areas of abnormally large ƒoF2 extend from the sunlit hemisphere across to the night hemisphere. Equivalent current systems of the magnetic variation coincide qualitatively with the ƒoF2-distribution patterns. An explanation for this anomaly is given which takes into account the horizontal drift motion of electrons in the F2 region that is caused by the interaction of the electric field deduced from the magnetic Sq and Sd variation with the magnetic field in the polar regions. Time variations of the ƒoF2 worldwide distribution and of the F2-region behavior as recorded on ionograms seem to support the drift theory.