Nocturnal Sporadic-E Activity at Two Southern Hemisphere Stations over Three Solar Cycles

Abstract

Analyses are presented of monthly values of the occurrence of the ionospheric parameters j~ E; and foE; for the South Pacific stations Christchurch and Rarotonga over three complete solar cycles. For each station both pre-midnight and post-midnight data show seasonal variations similar to daytime with the high latitude station showing a winter enhancement. Data fluctuations of scales longer than a year are very pronounced compared with variations in other ionospheric parameters. No correlations exist between any of the data sets and either the sunspot number Rz or geomagnetic index. Long-term variations in fi.E, and fo E; are uncorrelated at a particular station.