The initiation of lightning in thunderclouds: The possible influence of metastable nitrogen and oxygen molecules in initiating lightning streamers

Abstract

An examination is made of the possible role of metastable molecules of oxygen and nitrogen to contribute to the difference between the observed breakdown field in air of~25 kV/cm and the electric fields observed in thunderclouds which generally have a maximum of~3 kV/cm, which suggest much lower breakdown fields. Analysis of steady state equations for electron, ion, and metastable densities indicates that reductions on the order of a factor of 5 are possible in the electric field necessary to sustain a steady state discharge because of (1) electron detachment from negative ions by the oxygen metastable molecules and (2) increased ionization through deexcitation collisions of electrons with metastable nitrogen vibrational states, assuming high vibrational temperatures of the order of the electron temperature. However, solution of the time-dependent equations for the particle densities indicates that for a uniform discharge, times on the order of 0.1 s are required for the production of sufficient densities of the metastable particles from initial electron densities of~10 11 cm À3. In such times, electron diffusion would have dispersed electrons from any initial narrow electron pulse postulated to be produced by cosmic rays. It is concluded that the role of the metastable molecules, particularly the nitrogen vibrational states, is unlikely to be significant in the initiation of lightning streamers.

Distribution of inception times in repetitive pulsed discharges in synthetic air

“…We think that by opening the vessel we allowed H 2 O to enter the vessel. From [42] we know that H 2 O is an effective quencher of excited O 2 and N 2 states which could correspond with the removal of the second peak. Since H 2 O is not easily pumped out of the vessel we required a week to obtain the original synthetic air composition of 80% N 2 and 20% O 2 .…”

Experimental investigation on streamer inception from artificial hydrometeors

“…In thunderclouds, cosmic rays can produce the free electrons that are required for the inception, and Dubinova et al [14] predicted that to initiate a discharge, 100 free electrons cm 3 are required. Another possible free electron source is electron detachment from metastable oxygen and nitrogen, as suggested by Lowke [34]. In our experiment, we exert the experiments under repetitive pulsed conditions.…”

Possible scenarios for the initial acceleration of electrons of the core of ball lightning

“…Probably, the typical values of are greater than those of by several tens of per cent, for the following reasons. The region in which the electrons are accelerated also contains excited molecules and atoms, the collisional ionization cross-sections of which are greater than , and (Raizer 2009; Lowke 2015). At of the order of , some of the collisionally excited molecules and atoms undergo quick tunnel ionization (Bethe & Salpeter 1957; Delone & Krainov 2001) and, therefore, some of the excitation events are equivalent to ionization (Shmatov 2015 a ; see also appendix A).…”

“…Air contains about 78.08 % N 2 , 20.95 % O 2 and 0.93 % Ar (Kuznetsov 1965;Budyko 1988). Thus, σ (Raizer 2009;Lowke 2015). At E of the order of 10 6 -10 7 V cm −1 , some of the collisionally excited molecules and atoms undergo quick tunnel ionization (Bethe & Salpeter 1957;Delone & Krainov 2001) and, therefore, some of the excitation events are equivalent to ionization (Shmatov 2015a; see also appendix A).…”