ANGULAR SCATTERING OF RADIO-WAVES - IMPLICATIONS FOR MODE-COUPLING INTHE SOLAR CORONA

The solar corona is highly inhomogeneous. The magnetionic modes may th erefore couple under certain circumstances, and the polarization prope rties of solar radio sources may, as a consequence, be modified. An ap plication of the simple theory of mode coupling to the propagation of radio waves in the solar corona leads to the expectation that mode cou pling in quasi-transverse (QT) magnetic field regions should always be weak (coupling ratio Q much less than 1) at meter wavelengths. Observ ations to date suggest that, on the contrary, mode coupling is moderat e (Q similar to 1) to strong (Q much greater than 1) in QT regions at meter wavelengths. I suggest that observations and theory can be recon ciled by including the effect of turbulence on mode coupling. Specific ally, angular scattering on turbulent inhomogeneities greatly reduces the spatial scale relevant to the theory at low frequencies. As a resu lt, the coupling ratio is increased by a corresponding factor and mode coupling may be moderate to strong in QT regions at meter wavelengths .