  We extend the velocity channel analysis (VCA), introduced by Lazarian &
Pogosyan, of the intensity fluctuations in the velocity slices of
position-position-velocity (PPV) spectroscopic data from Doppler broadened
lines to study statistical anisotropy of the underlying velocity and density
that arises in a turbulent medium from the presence of magnetic field. In
particular, we study analytically how the anisotropy of the intensity
correlation in the channel maps changes with the thickness of velocity
channels. In agreement with the earlier VCA studies we find that the anisotropy
in the thick channels reflects the anisotropy of the density field, while the
relative contribution of density and velocity fluctuations to the thin velocity
channels depends on the density spectral slope. We show that the anisotropies
arising from Alfven, slow and fast magnetohydrodynamical modes are different,
in particular, the anisotropy in PPV created by fast modes is opposite to that
created by Alfven and slow modes, and this can be used to separate their
contributions. We successfully compare our results with the recent numerical
study of the PPV anisotropies measured with synthetic observations. We also
extend our study to the medium with self-absorption as well as to the case of
absorption lines. In addition, we demonstrate how the studies of anisotropy can
be performed using interferometers.
