The electron content of the southern mid-latitude ionosphere, 1965-1971.

Continuous accurate records of the electron content of the ionosphere are obtained at Auckland (ionosphere point at 34 deg S geographic, 38 deg geomagnetic) and at Invercargill (42 deg S geographic, 47 deg geomagnetic). Mean hourly values scaled from these records are used to show the average diurnal, seasonal and solar cycle changes in the ionosphere from June 1965 to August 1971. The mean daytime electron content shows no seasonal anomaly at any stage of the solar cycle, at 34 deg S. There is some anomaly at 42 deg S, particularly near solar maximum. The anomaly becomes quite marked in terms of peak density because of a contraction of the ionosphere in winter. The mean amplitude of the day-to-day fluctuations in electron content shows no appreciable solar cycle change.