Measurements of the magnetic field orientation in the Jovian ionosphere deduced from Pioneer 10 and 11 scintillation observations

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Abstract
In this paper we analyze the S band scintillations observed during the Pioneer 10 and 11 occultation measurements of Jupiter. We find that while the electron density irregularities are isotropic in the collision‐dominated lower ionosphere, they are anisotropic in the upper ionosphere because of alignment along the magnetic field. By using Rytov's approximation the frequency spectrum of the log‐amplitude scintillations is derived for a wave propagating in an anisotropic turbulent medium. It is shown that the spectrum depends to a large extent on the direction of anisotropy and is therefore useful for measuring the orientation of the magnetic field in regions that have not yet been probed by direct measurements. Applying this new technique to the Pioneer 10 and 11 observations, we deduce the first measurements of magnetic field orientation in the ionosphere of Jupiter.