A theory of the low current ionization waves (striations) in inert gases

Abstract

The solution of the Boltzmann equation found in the foregoing paper was utilized to calculate the dispersion of the fast as well as slow ionization waves (moving striations) in the positive column of a low-current neon discharge. Two balance equations of heavy particles were used: atomic ions guiding the fast waves and metastable atoms guiding the slow waves. The theory yields basically two kinds of waves: hydrodynamic r-variety and those waves that occur due to the spatial resonances of the electron gas: s-, s′- and p-variety, which are all experimentally known. Moreover, the theory predicts a new “p′”-variety as a fast wave with the same characteristic potential as the p-wave. Fixation of the characteristic potentials of the low-current ionization waves as well as high ratio of the group to phase velocity naturally follows from the theory as is shown by means of an approximative method. Numerical solutions are also presented giving full agreement for the optimum wavelength forE/p ₀≲3 V/cm. torr, but for higherE/p ₀ having by a few per cent lower values. The phase-shifts between various perturbed plasma parameters are also computed showing certain differences if compared with those expected from a hydrodynamic description but having in all cases the production term for the particles leading the wave in the right place demanded by the ionization mechanism of amplification and propagation of the wave.