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Re: Relativistic Runaway Breakdown Model for Lightning

Original poster: "Mike" <induction@xxxxxxxxxxx>

Hi Terry, Greg, List,
One of the people we work with here was at this conference 2/05 regarding the subject and also general issues X-ray / Gamma ray bursts found at discharge. So was the author pointed out here. One of the interesting points is sometimes the Gamma seems to be just before the discharge, other times just after the discharge. A big issue is that the satellite is having a problem resolving the 1 ms time because it is in a 550-600 Km orbit and it takes signal 1 ms to go 300 km.
So at this point it's a chicken or the egg question.
Also, a comment that not long back, somebody had asked about x-rays or gamma rays near TC's.
A friend at MIT told me last week somebody from this conference came by the Museum Of Science in Boston for the TC there with gear to seek both gamma and x-ray and found no trace of either type. However, he then went to a Marx generator and he got plenty. It was commented that the issue seemed more related to fast initial discharge rather than the quasi steady state discharge of TC's. I find it interesting that in some of these papers I am about to link to, it is noted the energy bursts seem linked to when step leaders are formed. I put together a bunch of papers from that conference of 2/2005 and zipped them up into one file.
At sea level, neither radiation goes all that far but at 15 Km, the range most think this lightning to gamma is at, the radiation range is more like 2.2 Km.
If the reader is into this subject, good reading can be had within the zip. Most are in PDF format once you unzip it.
Most are from the conference, a couple are older but related. www.hot-streamer.com/mike2004/GAMMA.ZIP
Regards,
Mike

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, June 02, 2005 7:15 PM
Subject: Re: Relativistic Runaway Breakdown Model for Lightning


Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Greg,

This is an interesting idea indeed! It would help explain why lightning seems to go where ever it wants to, often ignoring the rules of electrostatics that we think are in place. I wonder if the same effects could make a difference on even small coils since just a tiny bit of the effect could be dramatic in our micro scale situation.

I do not have access to the paper, but maybe we could get it somehow. The local college library should have it...

I was watching a lightning storm in the mountains today. It never seems to follow those E-field charts like it should. But this accelerated electron thing would help explain that! I one case the lighting traveled down into a valley and hit a metal building. From a pure electrostatic profile point of view, that should have been impossible... I decided it was wise to drive on when the strikes got consistently less than 200 yards away ;-)) But I guess the chances where pretty good it would ignore the antenna on my car (a local high point) given this new info ;-)

Maybe there is a chance this might lead to funding for a really big Tesla coil like someone we know has proposed :-)))


Cheers,

        Terry


At 01:04 AM 6/2/2005, you wrote: 
Hi All,

An interesting paper by A.V. Gurevich and K.P. Zybin appears in the May issue of Phys Today, titled "Runaway Breakdown and the Mysteries of Lightning." If you have access to a copy of Physics Today I strongly recommend reading this article.

One of the mysteries they address is how natural lightning can originate and propagate with an average electric field of only [200kV/m] -- an order of magnitude below what is needed to breakdown air at STP [2MV/m]. They provide a compelling argument that a relativistic electron chain reaction, initially triggered by a cosmic ray-induced shower, is the principal mechanism for generating the ionization necessary to trigger the main lightning strike.

The theory for Relativistic Runaway Breakdown states that as an electrons' energy increases, the braking force due to collisions decreases as 1/energy, until the electron starts to become relativistic and reaches a 'critical runaway energy' of 0.1 to 1MeV. At this point, if the electron is in an electric field greater than about 200kV/m it will actually accelerate; it's frictive forces now being less than the accelerating forces. The relativistic electron can now ionize other atoms, spawning new relativistic electrons in a chain reaction. The electric field cannot by itself originate the first relativistic electrons, as there's too much friction on the slow, classical electrons. However, a cosmic-ray-induced shower can provide the seed electrons. The authors provide a substantial amount of fascinating data, collected from both terrestrial observation stations and from spacecraft, to support their theory.

One of the collaborating researchers, G.Milikh, recently gave an interesting powerpoint presentation outlining the Relativistic Runaway Breakdown process, and how runaway electron beams can produce some of the diffuse, high altitude discharges observed between thunderclouds and the ionosphere. Milikh's presentation can for the present time be downloaded from here:
http://www.lc.leidenuniv.nl/lc/web/2005/20050509/presentations/Milikh.ppt

This theory has some very interesting implications for large coils.
Assuming classical electron behavior, there is a critical maximum size for a disruptive coil, beyond which it's ability to produce longer sparks falls to zero. This is due to the Fo larger coils becoming so low that the minimum possible time between firings starts to exceed the ion recombination times in air, allowing the arc channel to fully extinguish between firings.

However if one allows for relativistic runaway breakdown effects, there is a critical *minimum* coil size that reaches the state where only 200kV/m is needed to generate the arc channel. Both Gurevich and Milikh calculate that the characteristic length needed in air for the exponential growth of a relativistic runaway breakdown is about 50m.
Milikh suggests that the electric field needs to be supported over a length several times this, about 150m. To achieve this scenario, a twin coil system is required with a physical scale of about 240ft high, 50ft diameter each tower, and a tower to tower spacing of about 450ft. Each tower would need to generate a peak voltage of about 15MV. These are back-of-the-envelope calculations of course, but such a coil structure is arguably practical. Perhaps the most important point, however, is that there might not be a maximum limit on coil size, but rather a 'dead zone' between the maximum classical limit and the minimum relativistic limit described above.

-GL