Thermal energy density of dust in dusty plasmas: experiment and theory

A surprising observation in dusty plasma experiments is that the dust thermal energy density, P_{d}∝n_{d}T_{d}, is typically much greater than n_{d}T_{n} (where n_{d} and T_{d} are the dust density and temperature, and T_{n} is the neutral temperature), even though the dust particles would be expected to be in thermal equilibrium with the neutrals. We show here, theoretically and experimentally, that the anomalously high dust thermal energy density can be accounted for if electrostatic interactions between the dust particles and the background plasma are taken into account. Thus, the dust pressure in dusty plasma is mostly of electrostatic origin.