  A nonlinear time dependent fluid simulation model is developed that describes
the evolution of magnetohydrodynamic waves in the presence of collisional and
charge exchange interactions of a partially ionized plasma. The partially
ionized plasma consists of electrons, ions and a significant number of neutral
atoms. In our model, the electrons and ions are described by a single fluid
compressible magnetohydrodynamic (MHD) model and are coupled self-consistently
to the neutral gas, described by the compressible hydrodynamic equations. Both
the plasma and neutral fluids are treated with different energy equations that
describe thermal energy exchange processes between them. Based on our
self-consistent model, we find that propagating Alfv\'enic and fast/slow modes
grow and damp alternately through a nonlinear modulation process. The
modulation appears to be robust and survives strong damping by the neutral
component.
