  A model for element abundance fractionation between the solar chromosphere
and corona is further developed. The ponderomotive force due to Alfven waves
propagating through, or reflecting from the chromosphere in solar conditions
generally accelerates chromospheric ions, but not neutrals, into the corona.
This gives rise to what has become known as the First Ionization Potential
(FIP) Effect. We incorporate new physical processes into the model. The
chromospheric ionization balance is improved, and the effect of different
approximations is discussed. We also treat the parametric generation of slow
mode waves by the parallel propagating Alfven waves. This is also an effect of
the ponderomotive force, arising from the periodic variation of the magnetic
pressure driving an acoustic mode, which adds to the background longitudinal
pressure. This can have subtle effects on the fractionation, rendering it
quasi-mass independent in the lower regions of the chromosphere. We also
briefly discuss the change in the fractionation with Alfven wave frequency,
relative to the frequency of the overlying coronal loop resonance.
