Red shift of spectral lines in the Sun´s chromosphere

An unexplained center-to-limb variation (CLV) of solar wavelengths has been known for 75 years. A theory is described which not only explains this variation but also predicts its amplitude without the use of any adjustable parameter. The model considered is based on the fact that the momentum transfer of the solar photons to the electrons of the atoms of the solar atmosphere produces secondary radiation due to bremsstrahlung. The energy of this bremsstrahlung radiation is taken away from the energy of the initial photons and leads to a red shift. No ad hoc parameters are used, and all constants are either fundamental physical constants or well-known solar parameters. The model can explain the variation of the CLV as a function of its position on the disk and near the limb, and even the change in the lineshapes especially near the limb