Using a kinetic model for low-frequency dust acoustic waves (DAW)
in a dusty
plasma, we have examined the effects of a dust-size distribution on their
propagation and damping. Both Landau damping and damping due to dust-charge variation are included. We consider Gaussian and power-law dust-size
distributions. In accordance with earlier results of Melandsø et al., we find that
the dust Landau damping dominates at short wavelengths. At wavelengths
longer than the Debye length λD0, the
dust-charge variation is generally
dominant. It is always dominant for the power-law size distributions that
we
have studied. We also find that if the upper and lower size limits of the
dust are
chosen so that the average dust size remains constant, regardless of the
power-law exponent γ, the wave properties are practically identical to
those of a
monosize distribution of the average dust size. For a Gaussian dust-size
distribution, Landau damping may be the dominant damping mechanism if the
dust plasma is tenuous (P[Lt ]1) and the width of the distribution
is large.
Dust-acoustic modes in plasmas with dust distributions and charge fluctuations
