Ionospheric parameters deduced from the Faraday rotation of lunar radio reflections

Abstract

The total electron content of the ionosphere has been determined by Browne, et al.,1 and Evans2,3 by deducing the rotation of the plane of polarization (Faraday effect) of lunar radio echoes from fading curves of two closely spaced frequencies. The Faraday rotation arising from the double passage of linearly polarized radio waves through the ionosphere is given by where ƒ is the frequency in cps, B the magnetic induction in gauss at ionospheric levels, θ the angle between the propagation path and the earth's magnetic field, δ the zenith angle of the propagation path, N the number of electrons per cm3, dh a height element in cm, and h1 and h2 the lower and upper limit, respectively, of the ionized region contributing to the Faraday rotation. Since ϕ is ambiguous in multiples of π, determination of absolute values of the total electron content of the ionosphere requires the use of two frequencies to resolve this ambiguity or a single frequency high enough (>400 Mc/s) to have a total Faraday rotation less than π radians at the time of minimum electron concentration.