"COLD
LIGHTNING"
Clarence L. Dulaney
e-mail cldtx1@sbcglobal.net
Abstract: "Cold" lightning is a very rapid discharge that does
not cause fires (1.124).
It is believed that this phenomenon has been
approximated by the "entrapped" air-arc experiments run by Peter and
Neal Graneau (2.213ff). They charged an 8m F capacitor to 20,000 40,000 V, then discharged it across 1 cm2 electrodes, 1 cm apart. The resulting
arcs between the electrodes created very bright light, thunderous noise, and
tore, but did not burn pieces of newsprint placed in the air chamber between
them (8).
INTRODUCTION
(Note that references are given as (a.xxx) where a indicates the reference number, and xxx the page number.)
There has for many years been questions about lightning: Why it occurs when tall, dark clouds are present; Why it is a bright, localized flash (in most cases); Why it is almost always associated with the loud noises of thunder; Why it sometimes starts fires, but many times does not?
Benjamin Franklin was aware that lightning was an
electrical phenomenon. He invented the lightning rod, among his many
innovations (3.162ff). This discovery was based on the observation that
lightning usually strikes the highest object in its path, and that it is
singularly attracted to pointed objects. The
Historically, people had noted that sparks, some with crackling noises, could be produced by friction, such as rubbing glass rods with fur, or by walking across a carpet. Laboratory experiments on static electricity produced fairly strong arcs with bright flashes and loud noises.
Later electrical experiments were found to produce nitric oxide (NO) in arcs, and indeed nitric oxide was at one time produced commercially by passing air through an arc (5.205)
.
EXPERIMENTAL
Uman (6.67ff) has a
comprehensive bibliography (up to 1987) concerning studies of lightning
flashes. Some of the studies were ground based, (particularly at the
By high speed photography, the speed of a lightning stroke has been found to be as high as 100,000 km/sec (7.76, 8.122). The diameter of the main lightning stroke is about 15 cm, (8.122), but may be as small as 3 cm (4.28). The average energy of a lightning strike is about 5 x 109 Joules (3.12 x 1023 eV) (3.166).
LABORATORY EXPERIMENTS
"Entrapped" air-arc experiments were carried out by Peter and Neal Graneau (2.213ff). Their apparatus consisted of an approximately 1cm3 cell with a plastic lid. At either end of the cell were 1 cm2 copper electrodes, spaced 1cm apart. Energy was applied to the electrodes by means of an 8 m F capacitor charged to voltages from 20,000 to 40,000 V. The resulting high frequency arc had a time constant of about 200 m sec. All the arcs produced brilliant flashes of light, and an extremely loud noise which required the experimenters to wear ear protectors. The copper electrodes showed evidence of melting, but a piece of newsprint between the electrodes was torn but not burnt (8). The energies (½ CV2 ) of the "shots" varied from 1600 to 6400 Joules (9.99 x 1021 3.995 x 1022 eV).
ENERGETICS
Experiments by C. L. Andrews (9.459), using a Kerr Cell to observe and photograph airarcs found that the arcs, rather than being initiated at one of the electrodes, actually began at the midpoint and proceeded toward both electrodes. This indicates that the energy at the electrodes first causes a plasma to form from the air molecules by decomposing them into ions. With enough ions formed, the air "breaks down", and the arc proceeds.
The question is, exactly what kind of ions are formed, and what amount of energy is required? Since air molecules will be assumed to be 80% N2 and 20% O2, the ions must come from this mixture. Table I (10.3-7ff) gives a summary of the possible reactions and the energies involved for the air system. Note that the reactions are all reversible, with the reactions as written requiring energy , and the reverse reactions producing (ideally) the same energy. Note also that about 50% more energy is generally required to produce electrons (by ionization) than to break the molecular bonds.
TABLE I
. ..BOND AND IONIZATION ENERGIES
.. ..REACTION .ENERGY, Kcal/Mole ..ENERGY, eV/Molecule
.. .N2 = N+ + N- .225.96 ..9.80
... ...O2 = O+ + O- ...117.97 ..5.12
..NO = N++ O- ..251 ..10.88
..N = N+ + e- .335.1 14.53
..O = O+ + e- .314.1 .13.62
.. N2 = N2+ + e- ..359.7 ..15.6
..O2 = O2+ + e- ..279.0 ...12.1
..NO = NO+ + e- ..213.3 ..9.2
It will be assumed that most of the ions of the plasma are N+, N-, O+ and O-, and that an average energy of 10 eV per molecule is required to produce them, and that an average of 10 eV per molecule is produced when the ions recombine, and that since the recombinants are oppositely charged ions, the recombinaton takes place rapidly. Some of the N and O ions react to form NO. (There is also some Ozone produced as an aftermath of lightning as is NO2 and nitric acid, (4.33) but these are not produced in the ionic reactions that cause lightning.)
In 1 cm3 of air (STP) there are roughly 2.69 x 1019 molecules. If all decompose into ions, each requiring 10 eV, a total of 2.79 x 1020 eV is required. As noted above, a minimum of 9 x 1021 eV is produced in the airarc experiments. This amounts to 33.49 eV per molecule. What happens when the ions recombine? Because the arc takes less than 200 m sec, the recombination must be fast. An intense flash of light with a uv component (8.216), and a large noise are produced by the recombination. Each of these phenomena requires energy. Note that since about 33 times the minimum energy to cause ionization is available, there may be multiple arcs.
LIGHT
Suppose light of 3000 Ε is produced. The energy required is hc/l or 6.63 x 10-12 ergs/molecule or 4.135 eV/molecule. This accounts for 41.3% of the energy supplied. If the wavelength of the produced light were different from 3000 Ε, the energy would be different also.
SOUND
According to Newtons sonic theory (11.197ff), a minimum painful noise requires an energy density of about 1000 ergs/cm2 sec. Suppose the observer in the Graneau experiments stands 1 meter away, and hears a sound of intensity 1000 ergs/cm2 sec. A sphere of 1 meter radius would have a surface area of 1.2566 x 105 cm2. Thus the total sound would be 1.2566 x 108 ergs or 7.8439 x 1019 eV. This would be 2.81 eV for each molecule reacting. The total for light and sound would be 6.945 eV per reacting molecule.
It should be emphasized that the energies for both light and sound production are quite approximate. It is, however, clear that a considerable portion of the total available energy goes into production of the two types of energy.
ENERGETICS OF "COLD" LIGHTNING
As mentioned above, considerable electrical charge may be built up in cumulonimbus clouds. Essentially the (cloud bottom, earth) system may be considered a huge capacitor (3.157). Suppose the cloud bottom is 1 km above the ground, and the voltage buildup is 1 x 105 V/m, or a total of 1 x 108 V, with a charge buildup of 50 Coulombs. This "capacitor" would have a capacitance of Q/V or 0.5 x 10-6 F (0.5 m Farad). The energy available (½CV2) would be 2.5 x 109 Joules or 1.56 x 1028 eV.
Suppose the cloud moves over a single tree in a field, which could act as a discharge point. The energy of the capacitor" could instantaneously ionize the air. People have noted that their hair "stood on end" when near the site of an impending lightning strike. High enough ionization causes the plasma to "break down" and a lightning flash to form. Suppose the lightning channel has a diameter of 15 cm (1.122). Such a channel 1 km long would have a volume of 1.767 x 107 cm3 and would contain 4.749 x 1026 molecules. Since the lightning stroke takes place in such a short time, the air molecules may virtually be considered "confined". (If the stroke has a velocity of 100,000 km/sec, the time would be 10-5sec.) The stroke could have an energy of 32.5 eV per molecule. As in the case of the airarc experiments, about 10 eV/molecule would be required to ionize the molecules, and would be produced when the ions recombined. Exactly the same amount of energy would be required to produce the light of the flash as in the lab experiments, (depending on the wavelength of the light)..
THUNDER
Somewhat less noise is produced by hot lightning than by cold lightning (1.124). Thus, more energy to start fires may be available in "hot" lightning.
Suppose that "painful" thunder is noted at 5 km from our lightning flash. A 5 km sphere would have a surface of 3.14 x 1012 cm2, and thus at an energy intensity of 1000 ergs/cm2/sec would require a total energy of 1.96 x 1027 eV. Since there are 4.976 x 1026 molecules in our "lightning channel", there would be 4.12 eV/ molecule causing the thunder in this particular case, which is somewhat higher than our estimate in the laboratory case, but may be off by a substantial factor.. Once again, it is clear that much of the total available energy of lightning shows up in the light and sound produced. Were this not so, a lightning strike would be truly destructive.
All the references on lightning mention that several flashes may occur in very close order. It will be noted from above that more energy is available than is necessary for a single stroke, so that speedy ionization, recombination reactions may occur in rapid succession, and multiple strokes may result.
CONCLUSIONS
It would appear from the analyses above, the airarc experiments of the Graneaus are at least a qualitative simulation of "cold" lightning, in that in both the energy is obtained by discharge of a high voltage capacitor. In both, it is proposed that the rapid ionization and recombination of air molecules acts to provide the plasma , and the resulting high energy for the arc. The produced light and sound accounts for a substantial portion of the total energy.
Diatomic molecules are necessary for the scenarios described above to occur. There must be ions which form and recombine to make essentially the same molecules to keep from upsetting the balance of the atmosphere (particularly the oxygen balance). There are about 1800 thunderstorms occurring at any instant around the world with about 100 lightning bolts per second striking the earth (4.8). There is some NO formed from chance reaction of nitrogen and oxygen ions, and this eventually leads to nitrates which fertilizes the ground covered by the thunderstorms, (and add a bit of "acid rain).
While polyatomic molecules can undergo interatomic rotation and vibration to distribute internal energy, diatomic molecules can only vibrate. Except at very high temperatures, vibration cannot break diatomic bonds, because bond strengths are 200 Kcal or more per mole. Electrical energy can cause the bonds to break more easily, particularly to form + and ions The plus and minus ions are attracted to each other, and can rapidly recombine, whereas neutral atoms combine only slowly, since "three-body" collisions are required for atomic combinations.
As shown above, considerably more energy is needed to form electrons and positive ions than to break the molecular bonds. Surely, some electrons are formed in lightning, but many more atomic ions are formed.
It is my pure speculation that "hot"
lightning may occur where there is no clear-cut
REFERENCES
1. P. Viemeister, "The Lightning Book", MIT Press,
2. Peter and Neal Graneau, "Newtonian Electrodynamics" World
Scientific Publishers,
3. A. Moore, "Electrostatics",
Anchor Books,
4. S. Kramer,
"Lightning", Carolrhoda Books, Inc.,
5. W. Latimer and J. Hildebrand, "Reference Book of Inorganic Chemistry", The MacMillan Co. NY, 1951
6. M. Uman, "The Lightning Discharge", Academic Press,
7. M. Uman, "Understanding Lightning", Bek Technical Publications,
8. P. Graneau, "Why Does Lightning Explode and Generate MHD Power",
Presented at the Cold Fusion and New Energy Symposium,
9. C. Andrews,
"Optics of the Electromagnetic Spectrum", Prentice-Hall,
10. J. Dean, Editor, "Langes Handbook of Chemistry, 12th Edition",
11. F. Crawford, "Waves,
© 1/26/03
Clarence L. Dulaney