Linewidth Differences of Neutrals and Ions Induced by MHD Turbulence
  We address the problem of the difference of line widths of neutrals and ions
observed from molecular clouds and explore whether this difference can arise
from the effects of magnetohydrodynamic (MHD) turbulence acting on partially
ionized gas. Among the three fundamental modes of MHD turbulence, we find fast
modes do not contribute to linewidth differences, whereas slow modes can have
an effect on different line widths for certain parameters. We focus on
Alfv\'{e}nic component because they contain most of the turbulent energy, and
consider the damping of this component taking into account both neutral-ion
collisions and neutral viscosity. We consider different regimes of turbulence
corresponding to different media magnetizations and turbulent drivings. In the
case of super-Alfv\'{e}nic turbulence, when the damping scale of Alfv\'{e}nic
turbulence is below $l_A$, where $l_A$ is the injection scale of anisotropic
GS95-type turbulence, the linewidth difference does not depend on the magnetic
field strength. While for other turbulent regimes, the dependence is present.
For instance, the difference between the squares of the neutral and ion
velocity dispersions in strong sub-Alfv\'{e}nic turbulence allows evaluation of
magnetic field. We discuss earlier findings on the neutral-ion linewidth
differences in the literature and compare the expressions for magnetic field we
obtain with those published earlier.
