Single-particle Langevin model of particle temperature in dusty plasmas

A model of heating a particle in a dusty plasma is developed to predict the particle kinetic temperature. A Langevin approach is developed, generalizing a familiar Brownian motion model. Particles are cooled by neutral gas while being heated by one of two mechanisms: fluctuating electric fields and randomly fluctuating particle charge. Expressions are derived for the particle temperature resulting from these mechanisms. In both cases, the balance of heating and cooling leads to a particle kinetic temperature that varies inversely with gas pressure. When a particle is electrostatically suspended against gravity, the temperature is independent of particle size when heated only by electric field fluctuations, whereas it increases with size when heated only by charge fluctuations. An experiment is reported to demonstrate the use of the model in analyzing laboratory data.