The physics of lightning

Ultraviolet pulses of 200 fs duration and low energy (/spl ap/0.2 mJ) have a sufficiently high peak power to ionize oxygen and nitrogen by three- and four-photon ionization, respectively. It is shown that the resultant ionization channel induces a lightning like discharge at half of the natural self-breakdown voltage in nitrogen or air. The laser triggered discharging process is studied by monitoring the voltage between two planar electrodes. The effects of oxygen on the induced breakdown is investigated. A complete theoretical model is presented to simulate: (1) the electron seeding; and (2) the evolution of the plasma of electron-ion in the applied field. The results of the theory verified by small scale experiments-are used to simulate the process of laser triggered lightning in atmosphere, and helps to define the parameters of a laser system for lightning protection. >

Femtosecond ultraviolet laser pulse induced lightning discharges in gases

We test the two most commonly used lightning return stroke models, Bruce-Golde and transmission line, against subsequent stroke electric and magnetic field wave forms measured simultaneously at near and distant stations and show that these models are inadequate to describe the experimental data. We then propose a new return stroke model that is physically plausible and that yields good approximations to the measured two-station fields. Using the new model, we derive return stroke charge and current statistics for about 100 subsequent strokes.

Lightning return stroke models

We investigated the possibility to trigger real-scale lightning using ionized filaments generated by ultrashort laser pulses in the atmosphere. Under conditions of high electric field during two thunderstorms, we observed a statistically significant number of electric events synchronized with the laser pulses, at the location of the filaments. This observation suggests that corona discharges may have been triggered by filaments.

/pdf/electric-events-synchronized-with-laser-filaments-in-5avap1unj5.pdf

Electric events synchronized with laser filaments in thunderclouds

Many outstanding problems in lightning physics are linked with a difference in macroscopic behaviour between positive and negative polarity. Such differences are referred to broadly as 'polarity asymmetry'. As specific examples, the positive and negative ends of lightning propagate at different speeds, with different degrees of steadiness, and with different radiated electromagnetic energy. Positive and negative flashes to ground transfer their charge in markedly different ways—negative flashes with multiple discrete strokes (often) and positive flashes with single strokes followed by continuing current. Positive ground flashes cause sprites and negative flashes do not (generally). Positive intracloud flashes send gamma radiation upward to space and negative intracloud flashes do not (generally). Speculative arguments are presented that all of these macroscopic asymmetries are rooted in the microscopic asymmetry in mobility for free electrons and positive ions.

https://iopscience.iop.org/article/10.1088/0963-0252/15/2/S12/pdf

Problems in lightning physics—the role of polarity asymmetry

An experimental station for research on lightning and lightning effects was built in the Massif Central (France) in 1973. The experimental procedure is an application of artificial triggering of lightning flashes by means of the wire and rocket technique, which has previously been shown to be valid by M. M. NEWMAN.

Research on Artificiallyu Triggered Lightning in France

LIGHTNING has been triggered artificially in the Massif Central by launching small rockets carrying a thin steel wire connected to the ground. During two investigations in 1973 and 1974, a total of 20 triggerings have been achieved. Photographic evidence establishes the existence of two kinds of luminous object, lasting several tenths of a second, which may be similar to some varieties of ball lightning.

Artificially triggered lightning above land

/pdf/triggered-lightning-hazards-1eys3otped.pdf

R. Fieux

Papers

Research on Artificiallyu Triggered Lightning in France

Artificially triggered lightning above land

Triggered lightning hazards