Mode Couplings and Conversions for Horizontal Dust Particle Pairs in Complex Plasmas

The normal modes for horizontal dust particle pairs in a complex plasma are investigated using two methods, a numerical calculation and a molecular dynamics simulation. The ion wakefield downstream of each particle and the variation of charge with particle levitation height are taken into account independently. It is shown that both mechanisms can create mode couplings or hybrid modes. As the modes hybridize, their frequencies are altered. Mode conversions and resonance instabilities are also observed and examined near the resonance points. The resulting power spectrum clearly resembles the experimentally observed high energy density signature for large crystals. The criteria for the occurrence of both the mode conversion and resonance instability are found to be accurately calculated by the double derivative of the interparticle potential, for both the ion wakefield and charge variation cases.