A novel model describing the probability-density function (PDF) of the irradiance fluctuations in a turbulent atmosphere is presented. The change in the PDF as turbulence strength increases is explained by postulating that the reduction of the transverse coherence leads effectively to splitting of the source to a number of secondary sources. Consequently, the observer detects a number of independent light sources simultaneously. The statistics of this superposition are different from those of a single source. An exact calculation based on this stipulation leads to a PDF that is practically log normal at low-level turbulence, transforms continuously, and converges to the exponential distribution at very strong turbulence. The plots of PDF moments fit between the log-normal and the K-PDF plots.
© 1988 Optical Society of America
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