forwardscattered

Forward scattering refers to scattering processes in which incident light or other waves are deflected predominantly in the forward direction, with scattering angles near zero relative to the original propagation direction. The angular distribution of scattered intensity is described by a phase function that often shows a peak at small angles, indicating a forward peak. A common summary of forward scattering is the asymmetry parameter g = ⟨cos θ⟩, which ranges from -1 (complete backward scattering) to +1 (complete forward scattering). Values near +1 indicate strong forward scattering, typically associated with particles larger than the wavelength, as in Mie scattering. In Rayleigh scattering, for particles much smaller than the wavelength, the distribution is more isotropic and g is near zero.

Forward scattering is a key factor in atmospheric optics, where aerosols and cloud droplets produce bright forward lobes that affect radiative transfer, visibility, and remote-sensing measurements. In astronomy, forward scattering by circumstellar disks, planetary rings, or interplanetary dust can create brightness asymmetries and influence interpretations of observed flux. In optical engineering and imaging, forward scattering can enhance transmission through turbid media but also complicate deconvolution and quantitative analysis.

Modeling approaches include the Henyey-Greenstein phase function as a simple analytic approximation, while Mie theory provides exact solutions for spherical particles. Radiative-transfer calculations often use approximations (such as delta-Eddington) to handle strong forward scattering efficiently. Forward scattering is contrasted with backward and isotropic scattering and is a common consideration across atmospheric science, astronomy, and optical physics.