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Lightning strikes near the Geronimo Creek Observatory in Central Texas. Photograph by Forrest M. Mims III.

Several aspects of research on the behavior of lightning at or near the surface of the earth can provide important opportunities for the amateur researcher. In this article, I will discuss the unknowns, the difficulties of research, a rough proposal for a research plan, and some references and the difficulties attendant to them.

The lightning rod could be considered the first practical electrical device. It was invented in 1752 by Benjamin Franklin, who seems to have gotten it right on the first try. Lightning rods were quickly installed on vulnerable structures worldwide, and lightning damage decreased immediately thereafter. The instructions given in Franklin's half-column article in Poor Richard's Almanack correspond closely with those mandated in the latest edition of the National Electrical Code.

For all its success, the lightning rod was immediately controversial. Does a lightning rod encourage or discourage lightning? Should the top of the rod be pointed, blunt, tipped with a ball (glass or metal) or branched? How big is the region of protection afforded by a lightning rod? Can a large array of lightning rods affect the weather in other ways?

Lightning protection practitioners have devoted their efforts to the protection of explosives, fuels, telegraph equipment, electric power equipment, and ultimately digital electronics. But the fundamental questions first asked in the mid-eighteenth century have not yet been answered.

It has long been the contention of many researchers and practitioners that cloud-to-ground lightning strikes can be prevented by altering the charge distribution between thunderclouds and the earth. This is typically done using lightning rods with a large array of needle-like pointed wires. The tip of each needle point provides a region in which the electric field intensity exceeds the breakdown strength of the surrounding air. The result is an ionization of the air near the array and a measurable flow of charge from the earth into the air.

Devices that do this have been manufactured for many years. One of the most impressive installation can be seen at the Memphis Airport, where the computer facilities of Federal Express are protected by an array of tall towers, each topped by an umbrella-shaped structure made of spiny, stainless-steel ‘barbed wire.' Less well known is that fact that both the United States Capitol and the Washington Monument are equipped with multi-point lightning electrodes constructed with the same philosophy.

The effectiveness of lightning-prevention (as opposed to protection ) devices remains an open question. They may very well be effective, but there has been no way to construct a properly controlled experiment to learn if this is so.

Lightning instrumentation can be surprisingly simple. There are two pieces of equipment. One is the apparatus for making Lichtenburg figures. This consists of a pair of steel plates, between which is sandwiched a piece of photographic film. One plate is connected to a lightning rod or similar structure that a lightning stroke would find tempting. The other plate is connected to ground. That's it. A lightning strike will produce a distinctive pattern on the photographic film which can be compared to patterns made under known conditions. These images provide a rough measure of the highest voltage to which the upper electrode was subjected and the polarity of that voltage with respect to the earth. It is theorized that 90% of lightning strokes are negative with respect to the earth, and the remaining ten percent positive. Most positive strokes are supposedly of higher magnitude than the more common negative strokes.

The other instrument used in lightning research measures the peak current through the lightning conductor. This consists of nothing more than a steel sewing needle that is taped onto the conductor. If, after a thunderstorm, the needle exhibits permanent magnetism, it is assumed that the lightning conductor has conducted a significant current. The magnitude of the needle's magnetic field corresponds to the maximum current through the mast.

A device that used a magnetized dip needle to measure the sewing needle's magnetism on a scale was once used for this purpose. The scale was marked in increments of hundreds of amperes. These devices were used through the 1940s, but they have likely disappeared by now.

If lightning research is important, and if useful instrumentation is so simple, shouldn't most of the major questions have been answered? What work is left for amateur scientists?

Practical research on natural lightning and its behavior near the surface of the earth is, like much weather research, terribly difficult. Commercially-obtained data is very rare and expensive to obtain. It is almost impossible to set up a controlled experiment to test a theory.

In lightning protection, which is the study of the interaction of lightning and people, there are two major difficulties. One is the fact that lightning often strikes without leaving a trace (more about this later). The other is that the field is surrounded with superstition, questionable expertise, legal ramifications, and inconsistent theories.

It is well known that lightning can strike and destroy the works of man (as well as the man himself) in spite of the most heroic preventative measures. What is less well understood is that lightning can seldom be persuaded to strike where we would like it to strike. This makes much lightning science a study in frustration.

Several famous examples serve to illustrate the point. In the 1930's, Westinghouse scientists wanted to study the properties of lightning strikes as pure science and to improve the lightning resistance of the electrical equipment manufactured by their firm.

Accordingly, they designed and constructed some thirty data-gathering stations. These consisted of a sturdy shed with a metal pole extending through the roof. Instrumentation (to be described later) was connected to the pole. The sheds were placed in locations throughout the eastern United States that were known to be subject to frequent lightning strikes. (My undocumented suspicion is that every Lightning Ridge in the Appalachians was adorned by a Westinghouse lightning station.) Frequent inspections were scheduled for each station.

After two years of normal thunderstorm activity in the areas where the sheds were placed, not one was struck by lightning. Finally, one station was struck. The evidence was conclusive because the shed and its instrumentation were completely destroyed by the stroke.

After this, Westinghouse moved its lightning investigations to a laboratory constructed atop the Cathedral of Learning at the University of Pittsburgh. Some data was collected there over the years. I personally witnessed one strike on the structure in 1988.

The General Electric Company was equally interested in the properties of lightning. Their strategy was to set up an observation post in a New York City office building near the Empire State Building. Space was sublet from an advertising agency at a propitious location, and cameras were placed at the windows. A dedicated telephone link was purchased so that an investigator from GE could be summoned in the event of an approaching thunderstorm.

Over two normal lightning seasons, the building was never struck during a thunderstorm. It was struck once on a clear day. When lightning finally did strike the building during a storm, it struck the side of the building where the cameras were not aimed.

In an area noted for lightning strikes, students of C. B. Moore, a veteran lightning researcher at New Mexico State University at Socorro, erected seven 20-feet steel towers equipped with instruments to evaluate different lightning rod configurations. Though instruments recorded more than 1,500 lightning discharges over the two-month life of the experiment, the highly-exposed towers were never struck.

With results like these, it is tempting to theorize that the best way to lightning-proof a structure is to equip it with lightning instrumentation.

But instrumentation is necessary, because without an eyewitness it is often impossible to tell whether a lightning has struck a particular object. The High Voltage Lab at Mississippi State University is equipped with a three megavolt impulse generator to evaluate electric power insulation, aircraft lightning-protection systems, and other vulnerable equipment. The impulse sends a blinding arc between electrodes placed several meters apart. Yet an aluminum electrode, polished at its tip, will sustain only the slightest nick after such treatment, if anything at all. That is because for all the thousands of amperes in a lightning stroke, the arc lasts only fifty microseconds or so, and much of its energy is dissipated in heat and light. Thus we're often hard-pressed to know whether our experimental apparatus has indeed been struck.

Yet there are many recorded instances of sustained, high-current strokes that heat metal beams to the softening point, fuse beach sand into fulgurites, and punch holes in heavy masonry. Other lightning flashes are reportedly so small that no thunder is present. Several researchers also contend that some major lightning areas of the world—Malaysia, Japan, Florida, and South Africa—have distinctive varieties of lightning.

This lengthy lament points up the need for improved ways of gathering data on lightning strokes. One vast improvement is already in place, and can be seen at http://www.lightningstorm.com . Here, the Vaisala Corp. posts a new map of lightning strikes throughout the United States every fifteen minutes. (Scroll to the bottom of the main page.) The data are gathered by a nationwide network of receivers, each tuned to respond to local lightning activity. Through computer-aided triangulation techniques, each lightning strike can be detected and its location determined. The firm makes its living by supplying very detailed lightning data for particular locales and customers. These are usually utilities and handlers of flammable substances who need to estimate their lightning risks.

This lightning detection and location system is truly amazing and yields data that are extremely useful. Yet it won't tell us if lightning has struck a particular flagpole, tree or building, nor the effect of that strike on the electrode itself. And it is in this precise niche that amateur scientists can make a significant contribution.

My proposal, therefore, is that serious amateur scientists consider setting up or observing a lightning mast. The location would have to be far away from overhead wires and tall buildings. While these restrictions would seem to limit the data-gathering to rural areas, urbanites like myself should be able to take advantage of existing lightning masts, such as tall metal streetlight poles (those along highways should be ideal,) flagpoles (preferably aluminum,) tall antenna masts, and downleads from lightning rods.

The possibility of vandalism makes the Lichtenburg apparatus difficult to use in an exposed urban or suburban environment. However, it should be possible to tape a steel needle onto the mast in an unobtrusive location.

The major task, no matter what the instrumentation, is observation and recording. The plan is similar to that of the earliest weather observations: many small observation stations, each of which reports to a central information clearinghouse. Results are posted regularly so that the observers and others can consider and thus theorize. Unlike weather observations, there is little need to know the time at which a strike may have occurred, because that information is available from the Vaisala web site. However, a photocell-equipped device could presumably be rigged to record and, perhaps, even photograph a strike on a specific object.

The only books on lightning that are easily available are those by Martin Uman, a researcher from Florida. While these are interesting from the standpoint of lightning geophysics, they do not address many of the more interesting aspects of the behavior of lightning near the earth. The classic work, Lightning, Volume 2,.edited by R. H. Golde (Academic Press, 1977), s out of print and rare in engineering libraries. This is most unfortunate, because it include such topics as the penetration of lightning through tunnels (this was discovered when explosive charges were detonated during the construction of tunnels through the Alps) and lightning protection for aircraft.

These tend to be less helpful to the unbiased researcher, but they do serve to point out the rather contentious atmosphere surrounding the field of lightning protection and to suggest opportunities for good research. Many of the articles referenced contain loud writing and weak science. The single Yahoo! discussion group devoted to lightning protection is fairly inactive, stiffly moderated and membership is somewhat restricted. It may, however, be of some use to the amateur scientist who can somehow pass muster.

Books and articles on lightning and lightning protection typically cannot be catalogued in any rational fashion. They appear in journals and library sections that concern:

A word about the last category is in order. In the 1970's, the IEEE Transactions on Nuclear Science had many more articles on lightning and electric arc behavior than would seem appropriate for a journal of this title. The best explanation, and this is only speculation on my part, is that the triggering circuits for nuclear weapons use plasma (i.e., arc-operated) switches. Such a switch consists of a pair of electrodes separated such that the circuit current will not arc between them under normal circumstances. However, if the region between the electrodes is ionized by a radioactive source, intense ultraviolet light, or (as is done most frequently) the discharge from a high-voltage source, an arc will form between the electrodes and will carry the circuit current. The resistance of this arc is very low and the action of the switch is very fast and can be precisely timed.

Since the military applications of this research are necessarily classified, articles published for public consumption generally emphasize civilian concerns, including lightning protection.