  The quasiclassical distribution function for photon density in the phase
space is obtained from solution of the kinetic equation. This equation
describes propagation of paraxial laser beams in the Earth atmosphere where
"collision integral" embodies the influence of turbulence. The anisotropy of
photon distribution is shown and explained. For long propagation path, the
explicit expression for fourth-order moment of light is obtained as a sum of
linear and quadratic forms of the average distribution function. This moment
describes a spatial correlation of four light waves, giving the information
about the photon distribution in the cross-section of the beam. The fourth
moment can be measured using two small detectors outside the central part of
the beam. The linear form describes the shot noise (quantum fluctuations) of
photons. The range where the shot noise exceeds the classical noise is found
analytically. Derived photon fluctuations are the valuable source of
information about statistical properties and local structure of the laser
radiation that can be used for applications.
