Theoretical explanation of the solar limb effect

Abstract

The general theory of relativity predicts a wavelength shift of the lines in the solar spectrum with respect to corresponding terrestrial lines by an amount of 2.12 × 10 −6. However, it is an established fact that at the extreme solar limb (at radial distances greater than about 95 per cent of the radius of the disk) the Fraunhofer lines exhibit a red-shift substantially exceeding the shift required by the relativity theory (the phenomenon will be referred to as limb effect). On the basis of the general theory of wave propagation in inhomogeneous moving media it is shown that the extreme red-shift values observed at the solar limb are produced by radial currents in the solar atmosphere due to an effect different from the familiar one which is responsible for the wavelength shifts observed at the inner parts of the solar disk.