Spectral characterization of the electron drift instability in a Hall thruster

Resumo

The Hall thruster is an electric propulsion device commonly used for station-keeping purposes in satel-
lites and in deep-space missions since 1971. This device generates thrust from the interaction between a plasma and

electromagnetic fields. Several aspects of this interaction and the thruster operation are still not well understood.
Recently, numerical simulations and experimental measurements have shown the occurence of a high-frequency,
low-wavenumber instability known as the E × B electron drift instability. This instability modifies the electron
cross-field mobility in the plasma and can affect the thruster efficiency.
In this study we perform numerical simulations of a SPT-100 Hall thruster using the particle-in-cell method.
We describe a two-dimensional model in cylindrical coordinates in which the axial and azimuthal directions are
kept, neglecting variations in the radial direction. Our numerical simulations show that the instability induces a

large-amplitude wave in the azimuthal electric field and the ion density, as expected. We proceed by character-
izing the frequency and wavenumber of this instability using a spectral analysis, and compute power-laws in the

resulting power spectra. Our results demonstrate that the plasma in a Hall thruster displays a turbulent behavior
with an energy cascade induced by the E × B electron drift instability. We also show that the microturbulence is
characterized by an inertial subrange which extends to scales smaller than 1 mm.