  Context. Magnetohydrodynamic (MHD) waves are ubiquitous in the solar
atmosphere. In magnetic waveguides resonant absorption due to plasma
inhomogeneity naturally transfers wave energy from large-scale motions to
small-scale motions. In the cooler parts of the solar atmosphere as, e.g., the
chromosphere, effects due to partial ionization may be relevant for wave
dynamics and heating. Aims. We study resonant Alfven waves in partially ionized
plasmas. Methods. We use the multifluid equations in the cold plasma
approximation. We investigate propagating resonant MHD waves in partially
ionized flux tubes. We use approximate analytical theory based on normal modes
in the thin tube and thin boundary approximations along with numerical
eigenvalue computations. Results. We find that the jumps of the wave
perturbations across the resonant layer are the same as in fully ionized
plasmas. The damping length due to resonant absorption is inversely
proportional to the frequency, while that due to ion-neutral collisions is
inversely proportional to the square of the frequency. For observed frequencies
in the solar atmosphere, the amplitude of MHD kink waves is more efficiently
damped by resonant absorption than by ion-neutral collisions. Conclusions. Most
of the energy carried by chromospheric kink waves is converted into localized
azimuthal Alfven waves that can deposit energy in the coronal medium. The
dissipation of wave energy in the chromosphere due to ion-neutral collisions is
only effective for high-frequency waves. The chromosphere acts as a filter for
kink waves with periods shorter than 10 s.
