"Ball lightning is a well-documented phenomenon in the sense that it has been seen and consistently described by people in all walks of life since the time of the ancient Greeks. There is no accepted theory for what causes it. It does not necessarily consist of plasma; for example, ball lightning could be the result of a chemiluminescent process. The literature abounds with speculations on the physics of the ball lightning."

Peter H. Handel in the department of physics and astronomy at the University of Missouri at St. Louis provided a detailed overview and advances his favored model of ball lightning:

"According to statistical investigations carried out by J. R. McNally in 1960 (J. R. McNally, "Preliminary Report on Ball Lightning" in Proceedings of the Second Annual Meeting of the Division of Plasma Physics of the American Physical Society, Gatlinburg, No. 2AD5 [1960], Paper J-15, pp. 1AD25), ball lightning has been seen by 5 percent of the population of the earth. This percentage is about the same as the fraction of the population that has seen an ordinary lightning strike at close range--that is, close enough to see the direct point of the lightning impact.

"Ball lightning was seen and described since antiquity, often by groups of people, and recorded in many places. It is in general described as a luminous sphere, most often the size of a small child's head. It appears usually during thunderstorms, sometimes within a few seconds of lightning but sometimes without apparent connection to a lightning bolt. In some cases, ball lightning appears after a thunderstorm--or even before it. Its lifetime varies widely, ranging from a few seconds to several minutes; the average duration is about 25 seconds. The lifetime of ball lightning tends to increase with size and decrease with brightness. Balls that appear distinctly orange and blue seem to last longer than average. Many of these general characteristics are based on the work of A. I. Grigoriev, who analyzed more than 10,000 cases of ball lightning (A.I. Grigoriev, " Statistical Analysis of the Ball Lightning Properties," in Science of Ball Lightning, edited by Y. H. Ohtsuki, World Scientific Publishing Co., Singapore, 1988, pp. 88AD134).

"Ball lightning usually moves parallel to the earth, but it takes vertical jumps. Sometimes it descends from the clouds, other times it suddenly materializes either indoors or outdoors or enters a room through a closed or open window, through thin nonmetallic walls or through the chimney. When it passes through closed windows, the lightning ball damages them with small holes about one third of the time. The balls have no observable buoyancy effect. All these attributes led the great Russian physicist Pyotr Kapitsa in 1955 to interpret ball lightning as an electrodeless discharge caused by a standing UHF waves of unknown origin present between the earth and the cloud; earlier versions of this idea date back to the 1930s.

"Scientists have since refined Kapitsa's speculation. The Maser-Soliton Theory, which I first described in 1975 (P.H. Handel, "Maser Theory of Ball Lightning" in Bulletin of the American Physical Society Series II, Vol. 20 [1975], No. 26), is the present-day version of the UHF discharge approach. I have been directing research on the Maser-Soliton Theory at the Kurchatov Scientific Center in Moscow since 1992. According to this theory, outdoor ball lightning is caused by an atmospheric maser-- analogous to a laser, but operating at a much lower energy--having a volume of the order of many cubic kilometers.

"In technical terms, the maser is generated by a population inversion induced in the rotational energy levels of the water molecules by the short field pulse associated with streak lightning. The large volume of air that is affected by the strike makes it difficult for photons to escape before they cause 'microwave amplification by stimulated emission of radiation' (the maser effect). Unless the volume of air is very large or else is enclosed in a conducting cavity (as is the case of ball lightning in airplanes or submarines and to a certain degree also indoors), collisions between the molecules will consume all the energy of the population inversion. If the volume is large, the maser can generate a localized electrical field or soliton that gives rise to the observed ball lightning. Such a discharge has not yet been created in the laboratory, however.

"The Maser-Soliton Theory is supported by three well-known facts. First, ball lightning never occurs on sharp mountain peaks, high-rise buildings and other high points that attract lightning and that are used for lightning research by specialists in atmospheric electricity. (Lightning researcher Karl Berger told me he spent his life registering and measuring hundreds of thousands of lightning discharges hitting his laboratory on top of Mount Salvatore in Lugano, Italy, without getting a trace of ball lightning.) The inability to observe ball lightning in such settings has led to widespread frustration and even skepticism about the reality of the phenomenon. But in fact, the field pulse of the lightning striking high, peaked objects is localized in a narrow cone that encloses a relatively small volume. According to the Maser-Soliton Theory, this environment precludes the maser effect. On the other hand, when lightning strikes the flatlands, the resulting field pulse is huge: about 10 kilometers wide and three kilometers high. Ball lightning thus keeps its secrets: it visits the farmer and avoids the scientist!

"Second, ball lightning is harmless inside airplanes and submarines or in homes that have a conducting frame. Again according to the Maser-Soliton Theory, the energy of the maser in such settings is limited to about 10 joules (contrasted to a limit of 109 to 1010 joules in the open air), too little to be dangerous to life.

"And third, open-air ball lightning often ends with a violent explosion, sometimes causing extensive damage. The explosion is particularly strange because it violently displaces conducting objects to a larger degree than dielectrics. For instance, electric connection boxes are sometimes extracted from within the walls of houses by outdoor ball lightning and thrown in the middle of the street. The Maser-Soliton Theory predicts that such spiking would occur when the load suddenly disappears. (When the discharge that was consuming the photons generated by the maser suddenly disappears, these photons get to live longer and to multiply instantly, unbounded by the maser effect. This proliferation triggers an even larger instantaneous avalanche of photons and a practically instantaneous exponential growth of the electrical field. The increase occurs too rapidly to cause electric breakdown or heating but could cause very large ' ponderomotive forces'--mechanical effects that can tear apart composite objects having varied dielectric constants.)

"The pioneering UHF discharge ball-lightning experiments of Ohtsuki and Ofuruton in Japan (Y. H. Ohtsuki and H. Ofuruton, 'Plasma Fireballs Formed by Microwave Interference In Air' in Nature Vol. 350 (1991), page 139) and the above-mentioned research at Kurchatov in Moscow (V. A. Zhil' tsov, C9. A. Manykin, E. A. Petrenko; and A. A. Skovoroda, J. F. Leitner and P. H. Handel, 'Spatially Localized Microwave Discharge in the Atmosphere,' in JETP Vol. 81 [1995] ,pp. 1072-81) have aided in the solution of the ball-lightning enigma. Now that we seem to understand the true nature of ball lightning, it is particularly unfortunate that no funds are available in the U.S. for the study and the controlled reproduction of this fascinating phenomenon.

"A focal point for ball-lightning research will be the Fifth International Symposium on Ball Lightning on August 26-29, 1997, organized by Y. H. Ohtsuki and H. Ofuruton from Tokyo Metropolitan College of Aeronautical Engineering (for information, send e-mail to ofuruton@kouku-k.ac.jp). I will be the U.S. ball-lightning representative on the International Committee; I can be contacted at handel@jinx.umsl.edu"

The scientific community is increasingly convinced that ball lightning is a real phenomenon (although there remain some skeptics). What could cause ball lightning, on the other hand, is a source of steady controversy. Earlier, we ran the above theory. John Lowke, a plasma physicist at the Institute of Industrial Technologies, CSIRO, in Australia, offers another theory about the phenomenon:

"Although there is at least one textbook on lightning that questions the existence of ball lightning and I have never seen the phenomenon personally, I feel that there is no question that ball lightning exists. I have talked to six eyewitnesses of the phenomena and think there is no reasonable doubt as to the authenticity of their observations. Furthermore, the reports are all remarkably similar and have common features with the hundreds of observations that appear in the literature.

"Ball lightning is typically described as a luminous ball one to 25 centimeters in diameter having about the intensity of a 20-watt incandescent lamp; the phenomenon usually occurs after a lightning strike. It almost always moves, has a top speed of about three meters per second and floats about one meter above the ground. The motion can be counter to the prevailing breeze and can change direction erratically. Ball lightning may last up to 10 seconds, whereupon the ball extinguishes either noiselessly or with a bang. There have been many observations of ball lightning inside of houses and even in airplanes. There have also been a number of observations of ball lightning passing through closed glass windows, with no apparent damage to the glass. Usually there is no discernible heat production, although a recent observation reported a wooden plank that was singed. Several people have reported the smell of ozone and nitrogen oxides associated with ball lightning and also static in a transistor radio.

"Scientists have struggled for decades to formulate a plausible explanation for the existence of a stable plasma ball. A hot globe of plasma should rise like a hot-air balloon, yet observations do not generally report such behavior. Why does such a ball move, usually counter to the wind? What energy source sustains the lightning ball, given that such a ball would be expected to diminish rapidly in intensity?

"There have been hundreds of papers, and at least three books, discussing ball lightning. Most theories raise more questions than they claim to solve. Probably the most famous theory was advanced by the Russian Nobel Prize winner Pyotr Kapitsa, who claimed that ball lightning is caused by a standing wave of electromagnetic radiation. But why should there be a standing wave of electromagnetic radiation? Other theories assert a variety of sources of energy for ball lightning, including atomic energy, antimatter, burning material or the electrical field from a cloud.

"There is no generally accepted theory of ball lightning. I have my own theory, published in the Journal of Physics D: Applied Physics, ("A Theory of Ball Lightning as an Electric Discharge" in Vol. 29, No. 5, pages 1237-1244; May1996). I propose that ball lightning is powered by the electrical field associated with dispersing charges in the earth after a lightning strike. The movement of the ball is controlled by the velocity of the electrical charge as it disperses in the ground after the initial period of electrical 'breakdown' that occurs at the moment of the strike. In my paper, I suggest that this discharge is similar to a corona discharge (as occurs around high-voltage transformers) and consists of a succession of electrical pulses that take place on a microsecond time scale.