Comparison of electron contents computed with satellite Faraday data from widely spaced stations

The analysis of satellite Faraday data by determining the best-fitting linear variation of ionospheric electron content with time is discussed, and a simple test of the validity of the computed results is given. One hundred and ninety-three records of Transit 4A from seven widely spaced stations in Europe have been reduced, and in some cases it has been possible to compare the results obtained from different stations for the same satellite pass. Fairly reliable values of the electron content can be calculated provided that the true variation of Faraday rotation with time has been efficiently sampled and that the true mean variation of electron content is nearly linear. The method appears to work best at middle latitudes, but becomes almost useless near the Auroral zone. Some anomalous electron content gradients have been found.