The mechanism of occurrence of lightning keeps a lot of secrets. However, thanks to the work of Academician Alexander V. Gurevich some of them managed to resolve, to lift the veil of mystery and explaining all the slender, but very subtle physics. On the new research mechanism lightning Academy Gurevich told himself.
The fact that lightning is nothing like an electric discharge in the middle of XVII century proved in the works by Benjamin Franklin. However, after the creation of the theory of electricity and the study of phenomena in a gas discharge, a new mystery: a bolt of lightning in the atmosphere occurs when the electric field, the intensity of which an order of magnitude smaller than predicted from laboratory experiments on the breakdown of the air environment. This puzzle and allowed at the end of the twentieth century, Alexander Gurevich, a member of the Physics Institute. PN Lebedev Physical Institute.
The solution is based on open Gurevich effect of runaway breakdown. It is this effect allows the avalanche of fast electrons accelerated by electric fields is much smaller than those that are required for the static breakdown of the air layer.
"The essence of the theory of runaway electrons, — says Alexander, — lies in the fact that electrons with an energy of 1 keV, the electric field can be accelerated in the gas (the acceleration comes from Cavanaugh to MeVa). That is, the electrons do not move fast as usual, and particularly accelerated, but it is the presence of gas. In 1992, when the first work on the observation of gamma radiation in the atmosphere, our group has developed a theory of runaway electron avalanche formation: not just run away, but form with an avalanche, this is called runaway breakdown. "
Alexander and his students have created a theory of the phenomenon, and he became a leader of the pilot areas in which in recent years has conducted verification of predictions of the theory. To verify the accuracy of the predictions were carried out laboratory and field experiments (of the Tien Shan mountain scientific station of LPI near Alma-Ata, in the mountains, where he created a range of equipment, such as installation of "The Storm"). For several seasons recorded initiated by cosmic ray extensive air showers (EAS) and gamma-ray and radio emission generated during a lightning strike. Gamma radiation is observed during a storm in the air experiments (on the aircraft, balloon, and spacecraft), and with the help of ground-based equipment. All these observations are in accordance with the duration of event registration can be divided into two classes. One class uses a short recording lasting about a millisecond or less — these are processes with a time resolution in the submicrosecond range. The second class of observations using a longer recording time — about a minute (subsecond processes). The Tien Shan station measurements of gamma radiation produced during the entire time the lightning discharge (on average 0.1-1 sec) at an altitude of 3340 to 3880 m above sea level.
"Now it is important not simply to observe during atmospheric discharge a large amount of gamma radiation (a large number of fast electrons), but also identified with atmospheric discharge. Not so long ago in the United States observed gamma-ray emission lasting about 100 ms before the lightning, when it is already on the idea of coming to the earth. We are now seeing 100-600 ms — is 3 orders of magnitude longer, in fact, we see gamma radiation during atmospheric discharge. From this we can conclude that almost all of the processes in the atmospheric discharge, accompanied by a large number of fast electrons, "- says the results of the academician.
Today Alexander Gurevich, perhaps the only scientist in the world, which synthesizes the most complete knowledge of the nature of lightning. Created a theory of this effect and run a series of experimental studies of discharges in the atmosphere (including satellite: at the end of 2011 is scheduled to launch a special satellite "Chibis", which will collect data on the storm phenomena "from above"), academician Gurevich is currently working on a comprehensive model of the phenomenon. He sees his task is to reconcile the data Tien Shan experiments with laboratory experimental data and take into account all possible factors. For example, the experimental data obtained in different seasons, different, and we need to understand why this is happening.
During a storm in the cloud, charged with negative ions produced an electric charge of about 10 km2 on the pendant (1019 negative ions provides 1 C). For example, if a cloud of 5 km, then discharge will be 300 Kl. Such an electric field, under certain conditions should induce sufficient conductivity in a cloud, or impossible to transfer the charge. There is a "thin cord" with a diameter of a few millimeters, warmed to a temperature 3500oS sufficient for conductivity. However, the electric charge is so large that it can not be placed in such a thin cord, and the discharge is occurring "on the trail" of the cord is in a channel with a diameter of approximately 5 m movement of charge from cloud to cloud or from cloud to ground occurs in several stage, as it were, step by step: the one charge that sat on the cloud droplets is transferred to the air ions, and is moving ahead thin cord-leader.
And when it comes to other clouds or the Earth, is the leader of the counter, they meet, and there is a flash. All the stored energy in about 50 microseconds converted into radiation. We see a flash of lightning, the temperature in such a channel reaches about 20 million degrees. The process of promotion lasts leader, conventionally, a minute — kilometer, a rate he crawls around 10 seconds from the cloud to the Earth. The very same discharge occurs within 50 microseconds, and the lightning speed of 108 m / s.
"The leader — a sort of thing that takes charge and distributes it in the space between, say, one second and a cloud, and then is burned is the discharge itself. During the movement of a leader, I believe, and there is a strong electric field, which can accelerate and multiply the electrons necessary for the continuation of the movement leader. This acceleration is accompanied by the emission of electrons in different spectral bands, from radio to gamma-rays, "- explains Gurevich.
New data on these emissions, particularly on emerging atmosphere of gamma-ray bursts pose increasingly detailed job experimenters: "We want to record at the same time a source of gamma rays and radio waves, and radio and direct and reflected from the Earth, then we can uniquely identify them source, ie, register the signals not only from the lightning bolt, but the leader. In addition it would be desirable to determine when the field reaches its maximum and where. It is also important to simultaneously measured more ultraviolet and low-frequency radiation, they must also provide the necessary details of the future model that no one has known. "
Building on the fundamental laws, scientists are building a large model of a natural phenomenon, which will have a very important practical applications.