The structure and voltage-current characteristic of a negative-corona
generation zone are analyzed for the cases of cylindrical and spherica
l electrodes. Using the Engel-Steenbeck model for the cathode sheath o
f glow discharge we have shown the presence of a minimum in the voltag
e-current characteristic curve of a corona ionization zone and have re
vealed a dependence of the current density at the minimum upon cathode
geometry.