  For paraxial propagation of scalar waves the classic electromagnetic theory
definition of transverse linear (TLM) and orbital angular (OAM) momenta of the
beam wave are represented in terms of the coherence function. We show in
examples that neither the presence of optical vortices is necessary for the
intrinsic OAM, nor does the presence of optical vortices warrant the non-zero
intrinsic OAM. The OAM is analyzed for homogeneously coherent and twisted
partially coherent beam waves. A twisted Gaussian beam has an intrinsic OAM
with a per-unit power value that can be continuously changed by varying the
twist parameters. Using the parabolic propagation equation for the coherence
function, we show that both total TLM and OAM are conserved for the free-space
propagation, but not for propagation in an inhomogeneous medium. In the
presence of the random inhomogeneous medium, the total TLM and OAM are
conserved in average, but the OAM fluctuations grow with the propagation path.
This growth is slower for beams with rotation-symmetric irradiance.
