[en] The individual roles played by cooling, ionization, recombination and ambipolar diffusion are quantitatively studied in an argon arc burning at atmospheric pressure. Complete and partial local thermodynamic equilibria are examined before, during and after cutting off the electric field. Electron cooling is represented by relaxation of the excited states of the atom, measurement of this parameter allows evaluation of the exact role of ionization in the electron density balance. The use of different arc chamber diameters allowed the contribution of ambipolar diffusion and that of electron-ion recombination, on the disappearance of electrons, to be isolated and the corresponding coefficients, Dsub(a) and α to be determined. (orig.)