Numerical investigations of a cylindrical Hall thruster
  A new 3 dimensional Particle-in-Cell code was applied to simulate the operation of a 100 W CHT thruster. In the simulation a spoke moving with a velocity of about 0.8 cm/\mu s was observed. The initial position of the spoke was found to be strongly correlated with the cathode placement. The simulation has shown that the depletion of neutral gas can lead to azimuthal asymmetry of the discharge and possibly to the spoke phenomenon. 
K. Matyash, R. Schneider, O. Kalentev, Y. Raitses, and N. J. Fisch
physics.plasm-ph