Electrostatic Modeling of Dust Impact Signals Based on the Expanding Plasma Cloud

Signals generated by dust impacting spacecraft can be detected by electric field instruments. These signals have been simulated by numerous models. However, few models can accurately characterize the expansion of the plasma cloud generated by dust impact. The COMSOL model presented in this paper provides a way to understand the expansion properties of ions and electrons. The model can also be used to analyze the various expected waveforms of dust impact signals as a function of different parameters, such as the spacecraft voltage and the ambient plasma temperature. The results show that close to 50% of ions and electrons in the impact plasma cloud are collected by spacecraft at weak spacecraft potentials and that a fraction of the ions is still collected rather than all of them streaming away from the impact location at V _SC > 0 V. The model also confirms that in the expanding plasma cloud, ions are in the form of plumes, while electrons diffuse in an isotropic manner.