Effects of azimuthally inhomogeneous flow field on high-frequency azimuthal instability and electron transport in Hall thrusters via 2D PIC simulations

Abstract Experiments with asymmetric gas supply have shown that an azimuthally inhomogeneous flow field can modify Hall thruster discharge behavior and enhance cross-field electron transport. Here, the inhomogeneous flow field is modeled by imposing an azimuthally nonuniform plasma-generation source. Two complementary two-dimensional particle-in-cell configurations are used: a radial-azimuthal model that resolves wall sheath dynamics and the coexistence of electron cyclotron drift instability, modified two-stream instability, and long-wavelength modes, and an axial-azimuthal model that allows the axial electric field to form self-consistently. The radial-azimuthal simulations show that flow field inhomogeneity mainly redistributes fluctuation energy during the early transient and has only a weak effect after nonlinear saturation. In contrast, the axial-azimuthal simulations show that, compared with the homogeneous case, the effective electron mobility increases by approximately 17.3%, 26.4%, and 23.6% for β inh = 8 % , 16%, and 24%, respectively. Further mechanism analysis indicates that the azimuthally inhomogeneous flow field modifies the self-consistent axial electric field and the electron drift, thereby reshaping the azimuthal instability spectrum. The resulting change in the intensity of azimuthal instabilities determines the correlation between density and azimuthal electric field azimuthal fluctuations, and thus controls the effective electron mobility.