Stokes parameters

Four real quantities— I, Q, U, and V—that describe electromagnetic radiation’s total intensity and its linear and circular polarization, including partially polarized and unpolarized light.

Polarization: A property of transverse waves describing the orientation and evolution of their oscillations. Stokes parameters quantify polarization alongside total intensity.
Stokes I parameter: The Stokes quantity equal to total electromagnetic intensity. It sets the overall brightness against which the polarization components are measured.
Radio astronomy: The study of celestial objects through the radio waves they emit or absorb. Radio observations use Stokes parameters to map polarized emission and magnetic environments.
Jones vector: A complex two-component vector describing the electric-field amplitudes of a fully polarized wave. Unlike Stokes parameters, it retains phase information and cannot directly represent unpolarized light.
Plane of polarization: The plane containing a wave’s propagation direction and its electric-field oscillation. Its orientation determines how linear polarization appears in a chosen reference frame.
Stokes Q parameter: The Stokes quantity measuring linear polarization along two perpendicular reference axes. It distinguishes polarization aligned with the chosen horizontal and vertical axes.
Cosmic microwave background polarization: The linear polarization pattern imprinted on relic microwave radiation by early-universe scattering and later gravitational effects. Its measurements are reported through the linear-polarization Stokes components.
Coherency matrix: A matrix of pairwise statistical correlations between components of a wave’s electric field. Its entries provide a matrix representation equivalent to Stokes data for polarization.
Degree of polarization: The fraction of a wave’s intensity contained in its polarized component. It is calculated from the Stokes values relative to total intensity.
Stokes U parameter: The Stokes quantity measuring linear polarization along axes rotated 45 degrees from the reference axes. It captures linear polarization orientation that Q alone cannot distinguish.

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