Comments on Protonospheric Content — ATS-6 Revisited

Abstract

The application of GPS observations to the determination of electron content has renewed interest in the question of how the electron content is distributed between the closer and more distant sections of the propagation path.

The ATS-6 radio beacon experiment of the mid-1970s enabled the electron content to be determined from both the modulation phase technique (which included the whole path out to 6.6 Re) and the Faraday effect (which gave an electron content biased towards the lower altitudes). The observations were also simulated using a mathematical model. Thus it was possible to consider the significance of the “protonospheric content” as the difference between the phase and the Faraday contents was usually known.

The paper presents results from those studies in the context of GPS work. It is shown that at certain times a significant fraction of the total content resides at high altitudes, and that if this is not taken into account significant errors can arise in the determination of the electron content.