Neutrons Born in Lightning

[Wilfried Heil]

Neutrons observed from lightning (B.M. Kuzhevsky - Moskow State University 2005)
http://www.informnauka.ru/eng/2005/2005 ... 5_65_e.htm

Experimental detection of neutrons coincident with lightning (Q.M. Ali - Nature 1985)
http://www.nature.com/nature/journal/v3 ... 773a0.html

It is speculated that these neutrons come from the fusion of deuterium in water vapor in the lightning channel, or otherwise from spallation processes.

In other experiments, high energy gamma rays have also been observed in correlation with natural as well as artificial lightning. The mechanism of their origin is still unknown.

[Carl Willis]

Very cool. I'll have to wait to get home before reading these papers, but the conclusions, if well-supported, bring up some wonderful fantasies in my mind involving weather balloons full of deuterium being set aloft in thunderheads. There is so little deuterium in the air that the figures reported for neutron yield are very surprising. Just a little more deuterium up there and people will be talking about borated plastic roofing.

-Carl

[Carl Willis]

The Nature letter Wilfried mentioned is attached.

If Nature complains (if "Nature calls?") because of not getting paid their ransom, I'll pull it down.

The experiment and results looks solid, but the calculations about total neutron yield per strike are mostly hand-waving. Their detector is an array of giant BF3 tubes. It would be nice to look at a research database and see who else in more recent history has cited this letter, to get an indication of where these kinds of studies have gone since.

-Carl

[tligon]

It occurred to me back in college that the voltage is certainly there.

The number we estimated then was 20 kV/meter. Better data are available now, I hope. The density is the problem. Room temperature air at low altitude would give a very short mean free path, against which the voltage gradient would be small. Typical estimates I've seen of lightning temperatures is around 20, 000 K, just a couple of eV.

Still, that temperature drops the density (with a bang) and there are magnetic channel effects going on. I never did discount the possibility.

Could be some interactions with dust, too (particularly spallation).

At high altitude, things get more interesting. Anybody familiar with sprints and sprites?

[Chris Bradley]

I've not read the paper, but if ever there were a time to question the effects of EMP on neutron detectors, then surely a lightning stike is such a time!?

For those who have read the paper - in your opinion have they effectively dealt with the EM radiation issues to ensure they've avoided erroneous results?

[Wilfried Heil]

The following contains a description of the "Gulmarg Neutron Monitor" in India. It has been modified for the detection of possible 2.45MeV neutrons from lightning, which now renders it less sensitive to the cosmic ray events for which it was originally built. So these would be the persons to ask about the present state.

http://www.icrr.u-tokyo.ac.jp/can/icrc2 ... 6-oral.pdf

Of course it would be good to know where the lightning stroke was, say by a sufficiently precise lightning detection system.

Tom - you're correct about the voltage in a lightning channel. How did you measure that? If you set up an electrostatic field mill under a thunderstorm, it hardly ever exceeds 25kV/m, far under the breakdown field strength for air which is 100x higher. Currents during the strike are usually around 20kA but can be more.

Artificial lightning is completely different in this respect. Here the high voltage is generated by e.g. a Marx generator, which immediately produces the field strength of >2.5MV/m and initiates a lightning strike. So the fusion rates apparently observed under such conditions should be much higher than those in natural lightning.

Carl - thanks for uploading the article. I agree that adding some deuterium would do wonders here. Maybe one could produce triggered lightning by fireing up a rocket with deuterated fuel (just a bit of it - a few % of deuterium in the fuel should be enough). The rocket only needs to go up ~300m and drags a wire with it.

[Chris Bradley]

For me, that prompts a second question; if there is a useful function gained in monitoring cosmic neutron pulses, as per this site's raison d'etre, then "which came first, the cosmic neutron burst or the lightning".

What I am asking is whether it is definitively possible to discriminate cosmic rays that *promote* lightning, through atmospheric ionisation by them, from the possible consequential lightning. Maybe the cosmic neutrons come first and help *cause* the lightning?

[Richard Hull]

I have known about neutrons in lightning for years. Unfortunately that was before I became very familiar with neutron counters. I could not imagine a more efficient and significant producer to EM/RF noise than a lightning bolt. All electronic neutron counters work in separating millivolt or less signals from noise. For me, the count confidence level in thunderbolt sized discharges is close to zero.

Slowed atmospheric neutrons would be detectable based on special gating or windowed gate circuitry designed to "dummy up" the counter during the strike. I would hope that this is done in all such efforts. Sufficient additional local ring down time would also be demanded, It would think, so that a re-radiatingn RF ringing of a local chain link fence or other delayed cabling issues would not create false counts. Lots to consider here based on the real limitations of electronic neutron counting. I sensed this in Carl's response, as well.

I like the deuterated rocket fuel idea based on some of Uman's, Univ of FL. older work of inducing lightning strikes. I have both of his books and a couple of his papers. As you may know, My friend Scott Fusare, (posts infrequently here), and myself are interested in Ball Lightning reports.

I love to hook my Keithley electrometer to a small antenna during local violent thunderstorms here during the summer. It is very instructive to watch the local environment charge and discharge with each hit.

Richard Hull

[Chris Bradley]

You can also try connecting a ferrite/coil directly to the sound card of a computer. (I am sure there are various circuits offered on the internet to improve that interface.)There are plenty of FFT programmes that can then discriminate the different frequencies and it is most interesting to watch. If you do this with a high enough sensitivity you may, seemingly, pick up bursts from around the planet and the frequencies become 'smeared' in time with the higher frequencies travelling faster than the lower frequencies, amongst other curious spectral characteristics.

In fact, now I write this, it has just occurred to me that this may be a useful and practicable means to monitor the magnitudes and timings of some of the 'EM smog' coming out of an operating fusor.

[Wilfried Heil]

The shielding of electronic detectors against such interference will be tricky, but it can of course be done, with due diligence. I think the group at Gulmarg did this well. The lightning does not strike the detector itself, but is recorded from a few km distance.

The idea of triggered lightning which inspired me is from M.M. Newman (in: Coroniti, "Problems of Atmospheric and Space Electricity", 1965). They used small rockets launched from a ship and also alternatively dragged a kite over the boat. Newman had proposed this in 1958 and then tried it out himself.

The more recent reports are by Uman and Rakov in Camp Blanding, Florida.

It should not be too difficult to spray some deuterium into the air in such an induced lightning experiment.
Since it is known where the lightning is going to hit, one could use bubble detectors placed at several distances close to the strike point, thereby eliminating any concerns about EMP.

I think the observation from MIR and all others afterwards of high neutron counts over the lightning zones in the tropics implies that these neutrons were not generated by cosmic rays.

[Frank Sanns]

If a lightning bolt is 10 cm in diameter and 2 km long then the volume of the channel is 15,700 liters. Divided by 22.4 liters gives 701 moles of gas at STP. Pressure drops with altitude so correcting for the pressure between sea level and 2 km up gives ~600 moles. In a storm the humidty would be near 100% (~2% water at 20 C) or even higher if water droplets are in the path so the numbers here would be the most bleak compared to reality. The tally at this point is then 2% of 600 moles or 12 moles of water and double that of hydrogen/deuterium. Mr. Avagadro says that makes 1.4 E 25 hydrogen atoms and 1.4 E 21 deuterium atoms. Not a bad fuel supply if those atoms can find each other. Of course at those energies maybe the H-H-H fusion of the sun occurs.

During close lightning storms, I have run my super BGO detector and my large He3 detector. I have manually listened and watched for any correlation of clicks with the lightning flashes but have yet to witness even one that I did not think was part of the normal background.

A good test would be to drop a few dozen bubble detectors with slip on temperature insulators and little parachutes from an airplane within the storm. Collect them on the ground and take a look. I could not imagine getting any closer to the action than that.

Frank Sanns

[hjerald1]

For another view on neutrons from lightning see attached below.

On the other hand x-rays from lightning seems much more firm....see below also for one of the more recent studies on the topic.

Same caveat as Carl's earlier post.......if the publishers of these two articles object, I will remove them.


Jerry

[Chris Bradley]

I made these quick calcs earlier

Fully saturated air at 40C = ~50g[H2O]/m3 = 1.7E24 molecules/m3
Assume H:D = 6400, D density = 2.5E14/cc
Assume cross section of 0.1barn at 300keV, two deuterons at 75keV so v=2.7E8cm/s
Reaction rate = 2.5E14.cm-3^2*0.1E-24.cm2*2.7E8.cm/s = 1.7E12reactions/s/cc

Assume cross section of 35millibarn at 20keV, two deuterons at 5keV so v=7E7cm/s
Reaction rate = 2.5E14.cm-3^2*0.035E-24.cm2*7E7.cm/s = 1.5E11reactions/s/cc

not sure if my cross sections are right, but somewhere around that order. All depends on the actual percentage of total deuterons in a high enough energy state, of course, but it shows how atmospheric pressures make fusion look 'easy'. This is a deception, of course, and relies on there being enough ions at high enough energies, this being the real unknown in this calculation.

[Frank Sanns]

There must be data on high pressure arc fusion somewhere. This most likely was done in the 1950s. It seems that data coupled with the reported neutron numbers and theory must be able to shed some light on these measurements.

Frank Sanns