Fried parameter

The Fried parameter, often denoted as \( r_0 \), is a measure of the atmospheric turbulence that affects the propagation of electromagnetic waves, particularly in astronomy and telecommunications. It characterizes the coherence of a wavefront as it travels through turbulent media, such as the Earth's atmosphere. In more technical terms, the Fried parameter quantifies the size of the area over which a wavefront (such as light from a star) remains relatively undistorted due to turbulence.