Dust acoustic solitons with variable particle charge: Role of the ion distribution

Dust-acoustic solitons of large amplitude with variable particle charge are studied using the Sagdeev quasipotential analysis. Two limiting casks of ion distribution are considered separately: Boltzman and highly energetic cold ions. It is;shown that in both cases only compressive (density) solitons are possible. The charge variation is not important in rarefied particle clouds, but becomes crucial-if the particle number density is sufficiently high. Analytical expressions far the range of Mach numbers where solitons might exist are obtained. It is found that solitons are allowed in the supersonic, regime, and that in:dense:clouds the width-of the Mach number;range remains finite for the Boltzmann ions, but tends to zero for highly energetic ions.