Lightningbolt

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A Lightningbolt is a series of lightning strokes. See also Lightning, as either a pre-cursor or follow-on to this article.

This article seeks to describe the inner workings of a single "strike" of lightning, from experiments, as described. In addition, the causes of the behavior of Lightning, in general, is described herewith. A Lightning "Bolt" is herein described as a series of Lightning "strokes".

[edit] A Lightning Bolt Dissected

A Lightning Bolt is not a single discharge of high-voltage, high-current electricity from a cloud. Rather, it has been proven to consist of a series of separate discharges Lightning "Strokes", separated by a series of definite expanses of time where no visible light is emitted, due to a phenomena known as damped oscillation.

[edit] Sequence of a Lightning Bolt

When the charge between either a cloud and the Earth below it, or between two clouds, builds to the point that the air between has been ionized sufficiently to provide a conductive path, a Flash-over occurs, and an electrical discharge takes place.

When filmed with a camera at 24 frames per second, the first discharge is very bright, and fills the first frame. Then, the next 4-6 frames are dark, indicating either severely lessened or non-existent current flow for those 4-to-6 frames (one-sixth of a second to one-fourth of a second).

The next discharge (or Lightning "stroke") appears slightly less brilliant than the first, indicating that it contains less current than the first; and the time interval before the following "Stroke" (dark frames) is longer - - being from 7-to 10 frames in length. The brilliance of the second discharge is noticeably dimmer, indicating even less current in the second "stroke".

The next or third "stroke" then comes, and is even more noticeably dimmer than the last, and is followed by 12-to-16 "dark frames". This set of sequences repeats, up to 10 or 12 times before the last discharge, which is very light, indicating current is considerably less toward the end.

With electronic theory applied, the sequence is known as damped oscillation. This phenomenon can be explained as follows:

The first discharge that occurs is a very high current flow, which builds up a very large magnetic field around the ionized air which forms the discharge path. This magnetic field exists in this instance the very same way that a magnetic feld is created any time current flows through a conductor of any kind. The difference is in the amount of time it exists, from the first expansion of the magnetic field to its collapse at the end of the current flow.

Toward the end of the first burst of current flow (or discharge), the voltage (or charge) at the source becomes depleted, and the current no longer is being pushed by the original charge. Instead, the magnetic field then begins to collapse. Since the magnetic field is now moving the opposite direction (inward instead of outward in relation to the current path), it begins to induce a voltage differential in the opposite polarity. This causes current-flow to cease in its original direction.

As the magnetic field continues to collapse, the induced voltage (or charge) in the opposite polarity builds up to the point where it now re-ionizes the air in the current-path, and becomes conductive once more, and a second "flash-over" occurs (in the opposite direction). However, at this point, the potential difference in the charge is smaller than the first time, since the current has done "work", heating the air in the current path (to the point where it becomes incandescent). In fact, the rapid heating and expansion of the air during this first discharge is what causes the initial "CRACK! or BOOM!" when the lightning strike first occurs (due to the "sonic-boom from the rapid expansion of the air).

The second dishcharge is less brilliant than the first, due to less current in the second "stroke", which gives rise to a slightly smaller magnetic field being generated. The noise associated with the sudden burst of current flow is also weaker, contributing to the "rolling" thunder associated with lightning.

As the current in the second "stroke" falls off due to the magnitude of the charge dropping off, the magnetic field again begins to collapse. Again, this causes the current in the discharge to continue past the point where the voltage or charge has depleted, thereby building up a voltage or charge of the opposite polarity. Then current flow again ceases, but the magnetic field now collapses completely, causing induced volatge to rise past the point of "flash-over", and the entire sequence is repaeated once again, but in the opposite direction. During this discharge, the current again does "work" in heating the air in the discharge path, and the induced voltage is again lower in magnitude.

This sequence continues until the induced magnetic field becomes weak enough that it can no longer induce enough voltage upon collaspse to sustain a discharge, and the lightning "strokes" come to an end, each one being less intense than the last. This is the description of "damped oscillation". This is what causes the lightning discharge to appear to "flicker" during the Lightning Strike. This also means that lightning is an "Alternating crrent", in opposition to the theories that it is either ground-to-cloud or cloud-to-ground! - - It is BOTH!

M. Bruce Corp, Sr. author of "ZZAAP! Taming EMI, RFI & ESD", published by Academic Press, 1990.