Frequency averaging for beam waves in weak and very strong turbulence

The scintillation index for a temporally partially coherent beam wave source is calculated in the narrow-band approximation for weak and very strong atmospheric turbulence. It is found that frequency averaging in weak turbulence is not affective for collimated and focused beams with sizes much less than the first Fresnel zone. In the limit of very strong turbulence, frequency averaging effect on the scintillations becomes large for large source sizes.