Eclipse Phenomena in Radio Astronomy

Abstract

A new field in astronomy — radioastronomy — was created by the introduction of radio waves in the observational technique. Naturally we meet here with numerous analogies of the optical phenomena including the eclipses and occultations of radio sources. In these phenomena the optical refraction is replaced by the electronic refraction whose existence is conditioned by the ionised medium, for instance, the ionosphere. The radio waves traversing such a medium, i.e. the mixture: ions + free electrons + neutral particles, will be refracted according to the law of refraction with the refraction index

$$ {\mu ^2} = 1 - \frac{{N{e^2}}}{{\pi m{f^2}}} $$

((6.1))

where N the number of particles per cm3 e their electrical charge and m their mass f the frequency of radio waves.