Plasma response to jump of insulator surface potential in ionospheric plasma environment

摘要

Once an arc occurs on a solar array in low Earth orbit, it might grow by taking charges from a remotely located insulator through a current path formed by the plasma. A laboratory experiment and a computer simulation are carried out to study the response of plasma to a sudden potential change of the insulator surface induced by arcing on a solar array in low-Earth-orbit plasma environment. The experiment gives an artificial potential jump to the insulator surface. The simulation employs a Monte Carlo particle-in-cell method in axisymmetrical two-dimensional space that simulates the laboratory experiment. When a set of simulation parameters as close as possible to the experiment is used, the unsteady response of the plasma observed in the experiment is reproduced very well. Once the insulator surface potential jumps up due to arcing, a positive sheath develops. If the neutral density is high enough to be of the order of magnitude of 10(18) m(-3), explosive expansion of the sheath is set off due to the feedback mechanism induced by ionization inside the sheath. The explosive sheath expansion alone, however, cannot explain the current path formation between the array and the insulator observed in the arcing experiment, and the importance of electrons ejected from the arc spot on the onset of arcing is pointed out. References: 12