Theory for the breathing mode of a complex plasma disk

A nonlinear equation of motion for the breathing-mode oscillation of a complex plasma disk is derived. Particles interact via a shielded Coulomb force with a Debye length lambda and are confined in a parabolic potential well. Damping is due to the Epstein drag force. This system is modeled as a circular disk having uniform charge and mass densities. The equilibrium radius R-0 and breathing frequency omega(br) are calculated as a function of lambda and d, the effective nearest-neighbor separation. For the unshielded Coulomb force (lambda-->infinity), omega(br)(2)=3. When R-0/lambda<1, omega(br)(2)-3 varies as (R-0/lambda)(2). When R-0/lambda>1, the value of omega(br) depends on d. In the plasma regime dlambda, omega(br)(2) increases linearly with R-0/lambda with a slope proportional to d. (C) 2004 American Institute of Physics.