How are lightning born? Scientists have proposed a fundamentally new fundamental mechanism

Scientists have proposed a mechanism according to which only natural intracloud dynamics are sufficient for lightning initiation in thunderclouds. This is a fundamentally new concept, because previously existing scenarios assumed the presence of auxiliary factors, such as high-energy cosmic ray particles. In addition, it turned out that the process of lightning initiation is similar to snowball growth: at each stage it unfolds on larger and larger spatial and temporal scales. The discovery allowed to find an answer to the question about the mechanism of lightning initiation, which remained unresolved for more than 250 years. The results of the study are published in the journal Scientific Reports.
Lightnings attracted mankind attention since ancient times when their occurrence was explained by action of supernatural forces, for example anger of gods. With the development of science in the 18th century, these natural phenomena began to be unequivocally associated with atmospheric electricity. However, until now the process of lightning initiation in thunderstorm clouds remains unexplained and tops the list of ten most important unsolved problems of lightning physics. Since lightning poses a danger to human life and health, as well as to the operation of electronic devices, it is necessary to know how to effectively protect against it. The most commonly used lightning rods actually attract electrical discharges but do not prevent them. In order to develop more effective lightning protection methods, it is necessary to figure out the causes of lightning and the mechanisms of its propagation.
Researchers first proposed a theoretical scheme explaining the process of lightning initiation step by step. According to this scheme, small ice crystals and water droplets in thunderstorm clouds – so-called hydrometeors – collide and create “bursts” of electric field, which generate a large number of differently charged particles – ions. If there are many such centers of ion formation in the cloud and they occur close to each other, their total electric charge gradually accumulates and creates a strong electric field that exceeds the breakdown threshold of the air.
Local field amplification on decimeter scale without any other external influences leads to formation of streamers – cold weakly conducting plasma channels. Subsequently, scattered streamers merge into a more viable three-dimensional network, inside which a lightning “germ” is formed in places where the highest currents are concentrated. Lengthening along the direction of the electric field, it turns into a full-fledged lightning channel. The characteristic scale of the process increases at each stage: bursts of the electric field occur at millimeter and centimeter scales, streamers are about a meter long, and the “embryo” of lightning is ten to one hundred meters long.
“Our work helped to solve one of the main problems of modern physics of atmospheric electricity. The proposed mechanism of lightning initiation has an experimental basis and, unlike earlier hypotheses, does not require fulfillment of any elusive conditions, such as, for example, presence of high-energy cosmic ray particles. The obtained knowledge will help to develop new methods of lightning protection”.