THE UNIPOLAR CORONA SPACE-CHARGE FLOW PROBLEM

The paper gives a critical review of old and new methods and formulas for unipolar ion flow in corona discharges, with special attention to the implications of the Deutsch assumption of ion flow along undistorted Laplacian electric field lines. Reasons for disagreements between methods are traced back to the basic assumptions made, and it is argued that approximations conserving ion flow are to be preferred to those conserving Laplacian equipotential surfaces. However, even using exact finite-element methods, the results may deviate markedly from experiments, showing that the current density distribution in the ionization region itself now remains the outstanding problem.