Non-additive surface and volume backscattering from a rough interface over a correlated random medium
Abstract
We compute the first-order incoherent backscattering cross-section of a rough surface over a half-space with randomly fluctuating permittivity, when the two random fields are correlated, so that surface and volume scattering are not additive. A non-orthogonal coordinate transformation flattens the rough boundary and turns the geometric roughness into volume sources of the same Helmholtz equation as the dielectric fluctuations, propagated by the same Green's function: both mechanisms and their interference follow from one calculation, with no equivalent surface currents and no prescription for the field discontinuity. The geometric part of the amplitude reproduces the small-perturbation kernel exactly, for any incidence angle, permittivity and profile function. The interference term is obtained for both co-polarized channels, with an explicit surface-dielectric correlation coefficient. The departure from additivity reaches twenty percent at full correlation, changes sign with that coefficient, and is governed by a balance condition and a coherence condition on the depth of the correlated layer. It carries no angular signature and shifts the co-polarized ratio by less than a tenth of a decibel, so an additive inversion absorbs it, biasing the retrieved amplitude of the dielectric fluctuations by tens of percent.
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BibTeX
@misc{franco2026nonadditive,
title = {{Non-additive surface and volume backscattering from a rough interface over a correlated random medium}},
author = {Mariano Franco and Esteban Calzetta},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.39897},
eprint = {2609.39897},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.39897},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Non-additive surface and volume backscattering from a rough interface over a correlated random medium
AU - Mariano Franco
AU - Esteban Calzetta
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.39897
UR - https://arxiv.org/abs/2609.39897
AB - We compute the first-order incoherent backscattering cross-section of a rough surface over a half-space with randomly fluctuating permittivity, when the two random fields are correlated, so that surface and volume scattering are not additive. A non-orthogonal coordinate transformation flattens the rough boundary and turns the geometric roughness into volume sources of the same Helmholtz equation as the dielectric fluctuations, propagated by the same Green's function: both mechanisms and their interference follow from one calculation, with no equivalent surface currents and no prescription for the field discontinuity. The geometric part of the amplitude reproduces the small-perturbation kernel exactly, for any incidence angle, permittivity and profile function. The interference term is obtained for both co-polarized channels, with an explicit surface-dielectric correlation coefficient. The departure from additivity reaches twenty percent at full correlation, changes sign with that coefficient, and is governed by a balance condition and a coherence condition on the depth of the correlated layer. It carries no angular signature and shifts the co-polarized ratio by less than a tenth of a decibel, so an additive inversion absorbs it, biasing the retrieved amplitude of the dielectric fluctuations by tens of percent.
ER -