Fine Particle Charging Rate Limit Modification to Grain Dynamics in Abrupt and Gradual Inhomogeneities

Gyro-phase drift is a guiding center drift that is directly dependent on the charging rate limit of dust grains. The effect of introducing a gyro-phase-dependence on the grain charge leads to two orthogonal components of guiding-center drift. One component, referred to here as grad-q drift, results from the time-varying, gyro-phase angle dependent, in-situ-equilibrium grain charge, assuming that the grain charging is instantaneous. For this component, the grain is assumed to be always in its in-situ-equilibrium charge state and this state gyro-synchronously varies with respect to the grain's average charge state. The other component, referred to here as the gyro-phase drift, arises from any non-instantaneous-charging-induced modification of the grad-q drift and points in the direction associated with increasing magnitude of in-situ-equilibrium charge state. Gyro-synchronous grain charge modulation may arise from either abrupt or gradual inhomogeneity in plasma conditions. This work assesses the feasibility of observing gyro-phase drift in Auburn's MDPX, and how gyro-phase drift might be used to test dust grain charging models in an experiment.