Peculiarities of the resonant structure of the electron distribution function in S-, P- and R-striations

S-, P- and R-striations, which can be observed in an inert gas dc discharge at low pressures and small current densities, are considered. Mechanisms of the resonant formation of the electron distribution function (EDF) in S-, P-, Q- and R-striation-like fields are discussed on the basis of an accurate numerical solution of the Boltzmann kinetic equation and from the standpoint of the analytical theory. For S-, P- and Q-resonances, the EDF has the form of maxima of equal magnitudes. The maxima move in the plane (energy, coordinate) along the resonance trajectories. In the case of R-resonance, alternation of the magnitudes of these maxima takes place. The cause of such behavior of the EDF is elucidated. The experimental investigation of the EDF in R-striations in neon has also been carried out. The probe voltage-current characteristics were measured in each striation phase. The EDFs were determined by the second derivative of the probe characteristics. The ill-posed problem of the computation of the second derivative was solved by the Tikhonov regularization method. Comparison of the results of the measurements with the calculations shows the adequacy of the developed theoretical notions about the resonant character of the EDF formation for both integer S-, P- and Q-resonances and non-integer R-resonance.