Authors: André Nicolov (Caltech), Paul Bellan (Caltech)

When surrounded by plasma, astrophysical dust acquires charge through collisions with electrons. The dust-plasma system is governed by its own unique dynamics, dependent on both the plasma and the dust properties. The equilibrium charge developed on dust grains is controlled by the energy distribution of electrons in the bulk plasma. Within the heliosphere, the plasma environment is dependent on dynamic solar processes which often result in non-Maxwellian electron distributions. These distributions influence the properties and behavior of astrophysical dust contained throughout the solar system, including the interplanetary medium, planetary magnetospheres, and outer atmospheres. A mechanism is devised for calculating the effects of varying electron distributions on dust charging and morphology, and this is applied to a range of plasma environments throughout the solar system. It is found that hot electrons dominate the charging process, such that small fractions of high-energy electrons cause significant changes to equilibrium dust charge. Calculated dust surface potentials and charge-to-mass ratios are compared to measurements.

Funding:
NSF/DOE Partnership in Plasma Science and Engineering via DOE Award DE-SC0020079