The influence of an azimuthal nonuniformity in the magnetic field, azimuthal variations of mass flow through the anode, and the effects of cathode location on Hall thruster operation have been investigated. The gas flow generated by the hollow cathode causes shortening of the acceleration zone in the azimuthal sector in which the cathode is located. This results in shortening of the erosion bands on the walls and increased heat production in the same sector. This effect has been experimentally observed in high power Hall thruster having hollow cathodes with rather large mass flow rates. A mechanism to produce this effect is given. An increase of the magnetic field in one of the azimuthal sectors causes distortion of the acceleration zone in the same sector. In the affected sector, the drift velocity of electrons (and their energy) decreases in the part of the acceleration zone located near to the anode; and, on the contrary, increases in the part of the acceleration zone located near the channel exit. The variation in the visually observed luminosity follows the latter of these effects. A decrease of the mass flow rate through the anode in one of the azimuthal sectors forces the acceleration zone to move out beyond the magnetic field maximum in the downstream direction. These last two effects have been confirmed by by experiments. INTRODUCTION Azimuthal nonuniformity of the wall erosion of a Hall thruster discharge chambers has been observed in tests'. The width of the erosion bands in the azimuthal sector where the cathode was located differed from that in other sectors. In the cathode sector the erosion belt * Copyright © 2001 by Y. Yashnov, J. McVey, C. McLean, E. Britt, Pratt & Whitney, San Jose. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. "*" Consultant. * Senior Propulsion Engineer, Member AIAA. § Propulsion Engineer Specialist, Member AIAA. ** Chief Scientist, Member AIAA. was always shorter on the outer wall -and was sometimes longer on the inner wall as compared with other sectors. In all these tests with different erosion bands, the mass flow rate through the cathode was a significant value (^10%) of the mass flow rate through the anode. This does not match the usual rule, where the ratio rhc/ma for typical Hall thrusters does not exceed several percent. In spite of the observed correlation between the shape of the erosion belts and rhc/ma an explanation of this effect has not yet been developed. A number of interesting effects caused by azimuthal nonuniformities of the magnetic field and the mass flow rate through the anode were observed in Hall thrusters. An explanation of those effects has also not been given. An explanation for these effects is developed in this work. NOMENCLATURE r, cp, z cylindrical coordinates; e, m, c charge and mass of an electron, speed of light; Te, ne temperature and density of electrons; mc, ma -mass flow rates through the cathode and anode; E, B -electric and magnetic field intensities; Vd, i)e drift and thermal electron velocities; Va atom velocity; a, /j ionization cross-section, mean-free path; O, Uc, Ua, Uoo potential, potentials of the cathode, anode, infinity; 1 American Institute of Aeronautics and Astronautics c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. Rout, Rin, d, /a outer and inner radii of the accelerating channel, channel width, length of the acceleration zone; DERIVATION OF THE BASIC FORMULAE Let us consider the expression for a Hall current in the acceleration zone: