Microscopic quantities in discharge in air obtained from an electro-mechanical experiment

The results of an experiment of impulsive electrodynamics Eur. Phys. J. D 15, 87 (2001)] are shown to be due to electrons and ions in run-aways. By fitting the theoretical values with the experimental data, the values of microscopic quantities, at present unknown, can be derived, thus opening a new field of research. The obtained quantities are three, namely: (i) the contribution to air ionization due to the current (mainly of run-aways) and characterized by a parameter ρ; (ii) the product ζ=n_ein_ie (where n_ei is the number of ions extracted by one electron in run-away and n_ie the number of electrons extracted by one run-away ion colliding on the electrodes in electrical discharges with temperatures (for non run-aways) of ≃4×10⁴ K); (iii) the reconstruction time constant of the high-energy tail of the distribution function, from which we can derive the concentration per unit time of electrons and ions which become run-aways. The value is useful for the theoretical explanation of the electronic noise with power spectral density inversely proportional to the frequency.