Direct evidence of gradient drift instability being the origin of a rotating spoke in a crossed field plasma

A plasma rotating spoke in a crossed field discharge is studied using 2D radial-azimuthal fully kinetic Particle-In-Cell Monte Carlo Collision (PIC/MCC) simulations. The model reveals the whole perturbation spectrum of gradient drift instability linear stage: Simon-Hoh, lower-hybrid and ion sound modes, providing direct evidence nature. two-fluid dispersion relation was utilized to analyze development instabilities charge separation effect incorporated fluid theory super-resolution signal processing method (multiple classification) applied obtain numerical frequency spectrum. simulated growth rate show excellent agreement with theoretical (real imaginary frequency) over investigated cases. most linearly unstable mode found be lower hybrid transition into m=1 macroscopic structure after saturation phase accompanied by an inverse energy cascade. In nonlinear stage, pronounced phenomena can occur when heating $\mathbf{E_{\theta}\times B}$ electron flow channeled front passage suffices provide enhanced ionization.