A signature of non-local plasma fluctuations in Thomson scattering

Thomson scattering from plasma fluctuations in a plasma layer with an electron density maximum is considered. It is shown that the scattering spectrum shape is highly dependent on whether the fluctuations are local or not local. Using the example of Langmuir fluctuations, we demonstrate how non-locality effects manifest themselves by the occurrence of the oscillatory structure in the spectrum. In our case, the non-locality lies in a limited damping and the coupling of fluctuations in different locations where the scattered waves are generated. At the same time, the non-locality may exist even if the damping length for the fluctuations is significantly less than the plasma layer width. The results of the paper show that taking into account the non-locality may be important for improvement of the fluctuation models and for interpreting the Thomson scattering experiments. Specific calculations presented in the paper allow for finding additional information about plasma parameters from Thomson scattering experiments.