The Physics of the Retograde Motion of the Electric Arc

The retrograde motion of the cathodic arc attachment point in a transverse magnetic field is examined and is attributed to the asymmetrical confinement of the cathode-spot plasma which results from the asymmetrical combination of the self and applied magnetic fields. The confinement of the cathodic vapor on the retrograde side of the microspot enhances the electron emission on that side, and thus favors the observed retrograde motion of the arc attachment point. The model is shown to be consistent with a number of the reported features of the retrograde motion and of the cathode spot.