3D PIC Simulations on Hall Thruster Electron Drift Instability: Influence of Magnetic Field on Electron Transport

TL;DR

The study addresses how magnetic-field configuration influences EDI-driven electron transport in Hall thrusters. It employs three-dimensional PIC simulations with realistic magnetic fields (Analytic-B, Strong-B, Weak-B) and enhanced macro-particle statistics to compute the correlation $\langle n_e E_y \rangle$, the instability-induced mobility $\mu'_{\mathrm{eff}}$, and the PIC mobility $\mu_{ez}$ during low-frequency breathing modes. Key findings show that realistic B-fields produce transport patterns markedly different from radial-only analytic fields, with asymmetric transport enhanced in low-field regions, and that $\mu'_{\mathrm{eff}}$ generally agrees with $\mu_{ez}$; 2D radial-axial profiles derived from these 3D results offer a path to improved reduced-dimensional models. The work supports the development of accurate 2D diagnostics for Hall thruster design by linking magnetic-field structure to anomalous electron transport while highlighting the need for further 3D physics and experimental validation.

Abstract

Three-dimensional particle-in-cell simulations are employed to investigate electron transport characteristics in Hall thrusters, with particular focus on how magnetic field configuration affects the electron transport due to electron drift instabilities. Comparing analytic and realistic magnetic field models reveals significant differences in electron transport patterns, where radial variations in field strength lead to asymmetric transport enhanced in low-field regions. The derived effective electron mobility shows agreement with direct simulation diagnoses, and the obtained two-dimensional transport profiles provide a foundation for developing more accurate reduced-dimensional models.

Figures (13)

• Figure 1: Illustration of the simulation domain.
• Figure 2: Magnetic field configuration (a) and 1D magnetic field strength at three radial positions along $z$ (b) of the Weak-B case (and the Strong-B case with doubled field strength). The $z$ and $x$ values represent grid indices.
• Figure 3: Results of the mean ion number density over time of three cases with different $f_{pn}$ of the Strong-B case.
• Figure 4: Results of the mean ion number density over time of three cases with $f_{pn}=10$ but different B fields. The black solid curve is a reference of the Strong-B case with $f_{pn}=1$.
• Figure 5: The correlation between the electron density and the azimuthal electric field of the Strong-B case evaluated using different time periods.