Self-consistent charging of complex objects in flowing plasma: Implementation and analysis in WarpX

Abstract

The charging of conducting bodies in plasma environments is a fundamental process with implications spanning astrophysical, space, and laboratory plasmas. Accurate modeling of this charging process is essential for understanding and predicting the behavior of objects interacting with plasmas. In this study, we present the implementation of a charging algorithm in the open-source particle-in-cell code WarpX, which enables the simulation of charging for arbitrary 3D geometries in a plasma. The algorithm is verified against analytical solutions from orbital motion limited (OML) theory for a sphere in a static plasma and against published numerical results for a CubeSat in a flowing plasma. We investigate the charging of debris in Low Earth Orbit (LEO) conditions, considering both spherical and realistic debris geometries generated using a custom tool. The simulations reveal that the debris surface potential oscillates at the plasma frequency Doppler-shifted into the lab frame, a phenomenon not previously reported. The oscillations are robust to numerical convergence tests and persist for irregular debris geometries. Reduced density simulations suggest a critical threshold below which the oscillations disappear. Contrary to some earlier studies, precursor solitons do not form in our realistic LEO simulations, even with self-consistent charging of irregular debris. This study demonstrates WarpX's new capabilities for high-fidelity simulations of object charging in plasmas and highlights the complex nature of plasma-object interactions. The insights gained can inform the development of debris detection and mitigation strategies, while the WarpX code provides a valuable tool for future research in this field.