Mode transitions in nonlinear evolution of the electron drift instability in a 2D annular E × B system

Abstract

Nonlinear development of electron drift instability is studied using 2D3V azimuthal-radial Particle-in-Cell simulations of an annular Hall thruster channel of 10 cm diameter. The full 2π azimuthal domain of the annular cross section is simulated with reflecting boundary conditions at the radial boundaries. It is shown that the instability, which starts as a short length scale linear instability, undergoes a sequence of nonlinear transitions into longer wavelength modes. The transitions in the mode wavelengths are accompanied by related transitions of the magnitude of anomalous axial current. In the nonlinear stages, there is evidence of azimuthal trapping and dragging of ions by the propagating wave resulting in saturation of instability. It is demonstrated that the size of the azimuthal domain influences mode dynamics and, thereby, the anomalous cross field electron transport.