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Non‐uniform motion and extended media effects on the mutual coherence function: An analytic solution for spaced frequency, position, and time
Author(s) -
Nickisch L. J.
Publication year - 1992
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/91rs02356
Subject(s) - mutual coherence , coherence (philosophical gambling strategy) , doppler effect , physics , diffraction , scattering , optics , coherence time , coherence length , fourier transform , computational physics , position (finance) , wave propagation , quantum mechanics , superconductivity , finance , economics
An analytical expression for the two‐frequency, two‐position, two‐time mutual coherence function applicable to propagation through thick random media with nonuniform electron density and plasma velocity is derived using the phase‐screen/diffraction method (PDM). In this method the ionization is collapsed to a number of thin screens and diffraction is developed in the free space between. The resulting mutual coherence function converges rapidly to the continuum result as the number of screens representing the medium is increased. The effects of multiple scatter occurring over long distances and varying plasma velocity over the propagation path are shown to be important in HF propagation. Scattering functions (delay‐Doppler power spectra) obtained as Fourier transforms of the PDM mutual coherence function are compared to scattering functions measured by an HF channel probe. Nonuniform velocity profiles are shown to account for the variety of delay‐Doppler couplings observed.