A model of cathode spot motion in a transverse magnetic field

A spot grouping and retrograde motion model based on previous study of the cathode thermal regime and the plasma flow in the near cathode region is proposed. The current per group spot is calculated by assuming that the plasma kinetic pressure is comparable to the self-magnetic pressure in the acceleration region of plasma jet. The results of the calculations indicate a linear increase of the current per spot group and retrograde spot velocity with the magnetic field and arc current, in agreement with previous experiments. The spot retrograde motion in a short gap and at atmospheric pressure arcs and the reversal motion in strong magnetic fields (> 1T) observed by Robson and Engel are discussed.