Some Ramifications of the Power-Law Spectral Index for Propagation Modeling

摘要

Accurate modeling of radio-wave propagation phenomena is important for verifying our understanding of the physics of ionospheric instabilities that structure the ambient electron density as well as predicting deleterious systems effects. New results in radio-wave propagation theory have quantified the relationship between the power-law index that characterizes the average striation size distribution and the signal structure under strong scatter conditions. This report discusses some ramifications for propagation modeling of these new theoretical results. The phase structure function and various functionals of it characterize the striation environment for predictive modeling. Two very different approximations to the phase structure function are currently being used. One, an asymptotic approximation, is valid when the one-dimensional phase spectral density function falls off less rapidly than f-3. The other, a quadratic approximation derived from the formal Taylor series expansion of the phase structure function, is valid when the one-dimensional phase spectral density function falls off more rapidly than f-3. The f-3 power law marks an important transition in the behavior of the complex signal moments. For the f-3 and more steeply sloped phase spectral density functions, the large-scale structure exerts a strong influence on the signal statistics.