Method for super Fresnel resolution in electromagnetic diagnostics of inhomogeneous plasma

The method of electromagnetic diagnostics is suggested, which promises to perform super Fresnel resolution of plasma inhomogeneities, that is resolution, distinguishing details smaller than Fresnel radius. To realize super Fresnel resolution it is suggested to represent the wave field of the source in the form of double weighted Fourier transform (DWFT), deals with Fourier transform simultaneously in coordinates of the sources and in coordinates of receivers. Important property of DWFT is that DWFT transfers into geometrical optics (GO) approximation for smooth inhomogeneous media and becomes equivalent to the Rytov or to small angle Born approximation in the case of weak inhomogeneities. As a result, inverse DWFT allows obtaining linear integral of plasma density both for large scale inhomogeneities, as in GO approximation, and also for inhomogeneities, whose transverse sizes are small as compared with Fresnel radius. DWFT embraces also the results of the phase screen method and allows to take into account phenomenon of micro-multirayness and to describe strong amplitude fluctuations.Using inverse DWFT algorithm, the authors study resolution of systems consisting of discrete sources and receivers. Both analytical estimates and the results of numerical modeling evidence opportunity to observe small scale plasma inhomogeneities with super Fresnel resolution.