. The magnitude of the refractive index fluctuations is usually measured in terms of Cn^2, the structure constant of refractive index fluctuations, which is the spectral amplitude of refractive index fluctuations in the inertial subrange of turbulence. Some types of scintillometers, such as displaced-beam scintillometers, can also measure the inner scale of refractive index fluctuations, which is the smallest size of eddies in the inertial subrage. Scintillometers also allow measurements of the… (More on Scintillometer)