Scattering of Electromagnetic Energy in a Randomly Inhomogeneous Atmosphere

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Abstract
First‐order perturbation theory is used to evaluate the scattered power at a receiver resulting from random inhomogeneities in the propagating medium. The integral expression for this scattered power is equivalent to the expressions as used by Pekeris and Booker and Gordon. However, it is shown that it is not appropriate to use a space correlation function of refractive index as defined by the above authors. Instead, this paper defines a time correlation function of refractive index which permits formal evaluation of the time average scattered power. It is also shown that, whereas a space correlation function of refractive index is not amenable to direct experimental evaluation, the time correlation function as defined in this paper is directly measurable. Finally, it is shown that for so‐called small‐scale turbulence the average scattered power does not depend appreciably on any particular model of atmospheric turbulence, whereas for large‐scale turbulence the frequency and scattering angle dependence of the scattered energy is affected greatly by the particular time correlation function chosen or by the assumption that scattering is the result of randomly located spheres.