Interstellar Scintillations of Polarization of Compact Sources.

We demonstrate that the measurement of fluctuations of polarization due to the Galactic interstellar scintillations may be used to study the structure of the radiation field at compact radio sources. We develop a mathematical formalism and demonstrate it on a simple analytical model in which the scale of the polarization variation through the source is comparable to the source size. The predicted amplitude of modulation of the polarized radiation flux is approximately 20%pismsc, where pis is the characteristic degree of polarization of radiation at the source and msc is the typical modulation index due to scattering, i.e., msc approximately 1 for diffractive scintillations and msc<1 for refractive scintillations.