Non-local effects in spatial distribution of excitation rates in positive column of glow discharge plasma of molecular gases

At simulations of gas-discharge plasmas the electron distribution function (EDF) is usually calculated using a local approximation (LA) which is applicable only when electron energy relaxation length \textit{le} $< \quad R -- $plasma size. For atomic gases \textit{le} $> \quad 100l$ ($l$ -- electron free-path-length), so the LA for EDF is not valid up to high pressures. By contrast, in molecular gases due to strong vibrational excitation with low energy threshold, the length \textit{le} is small \textit{le$\sim $l}. And so it is assumed everywhere that the LA for EDF calculation in molecular gases is valid in any cases when diffusive approximation $R $>$ l $ is applicable. In this report it is shown that in molecular gases local approximation is inapplicable on the discharge periphery, where ambipolar field exceeds longitudinal field. A heating of fast electrons in ambipolar field gives rise to excitation constants from centre to periphery of discharge.