Observations of ionospheric electron content at medium latitude geomagnetically conjugate stations

Electron content data recorded at Cold Bay, Alaska and Invercargill, New Zealand have been used to study the geomagnetic conjugate effects. The correlation on day-to-day variations at these two stations is found to be negative at extreme magnetic quiet and it then increases to positive values with magnetic activities. When disturbed magnetically, the correlation is + 0.73. Evidence is presented to show that, on the first day following the sudden commencement, the afternoon rise and the subsequent pre-sunset fall in electron content is controlled geomagnetically.