Total ionospheric electron content at middle latitudes during sunspot minimum

Abstract

A technique is presented which allows values of total ionospheric electron content deduced from recordings of Faraday rotation rate, made on a single frequency, to be corrected for the effects of NS gradients in electron content. Results obtained by the use of this technique are presented for three stations situated at middle latitudes of the southern hemisphere. Some of these results are compared with corresponding results obtained from the more accurate technique which makes use of dispersive Faraday rotation. This comparison indicates that systematic errors due to gradients can be virtually eliminated and shows that in the case considered the remaining random errors have a spread of about ±8 per cent. For daytime results the spread is only ± 5 1 2 per cent. The ionospheric electron content at midday was observed to be on the average 1·5 times larger in summer than in winter. At night the electron content decays towards a constant value of about 0·3 × 10 17 electrons/m 2 rather than towards zero. There is also a suggestion in a few cases of a minor peak in electron content around midnight. The observing stations differ only slightly in latitude, but in general an increase of electron content towards the equator is observed. Results from satellites observed at Sydney are combined with results from ionosondes to give values of ion temperatures near the peak of the F2-layer. At night temperatures as low as 550°K are observed in winter, and as low is 675°K in summer. The maximum daytime temperatures are 775°K in winter and 1000°K in summer.