It seems like when you see clips of lightning striking in the American Midwest, the lightning is far away and appears to be fairly large in width given the distance from the camera. And then when you see clips of a tree that is 20 feet away getting struck, the bolts of lightning appear about the same width as those that could be miles away.
So my question is, is the apparent similarity in width between distant bolts and close bolts just a coincidence or a case of selective memory on my part? And most importantly, on average, how "wide" is a bolt of lightning?
I know it can be as small as 0.01" in diameter, and recall from classes that it usually is about 1" or less initially.
Of course the plasma expands quickly and looks/gets bigger.
These numbers were found by having lighting pass through some mesh, with the resultant hole that was left being the determinant of diameter.
Also there were fused sand particles where strikes occurred that were used to estimate.
The problem is, what do you call the diameter? The initial conduction? The plasma at the very start? After it has a chance to expand slightly?
The apparent diameter in pictures I've taken seem to be just what is visualized with the very high contrast between the surrounding air, usually almost dark, and the very hot spark.
I know this is not scientifically exhaustive, but a gathering of recollections from some papers and weather texts.
That's a great response, Dale... it's all relative to what's being defined, isn't it! And since a 'stroke' is almost always a series of 'impulses', at what point in time, and which impulse?
AND which energy form, is creating the effect "observed and asked about'...(light, heat, noise, Magnetic influence, Electricl charge, etc..) and 'distance to notice the effect'... how wide is 'heat'.... heh... somebody can get rich and famous if they can nail THIS down, probably would mean a true 'Unified Field' theory, and lead to unlimited energy, ant-gravity, FTL transport, ...
(2021-01-03, 21:54)Dale.Reid Wrote: [ -> ]I know it can be as small as 0.01" in diameter, and recall from classes that it usually is about 1" or less initially.
Of course the plasma expands quickly and looks/gets bigger.
These numbers were found by having lighting pass through some mesh, with the resultant hole that was left being the determinant of diameter.
Also there were fused sand particles where strikes occurred that were used to estimate.
The problem is, what do you call the diameter? The initial conduction? The plasma at the very start? After it has a chance to expand slightly?
The apparent diameter in pictures I've taken seem to be just what is visualized with the very high contrast between the surrounding air, usually almost dark, and the very hot spark.
I know this is not scientifically exhaustive, but a gathering of recollections from some papers and weather texts.
Another issue is the apparent visual size of a multi-stroke lightning flash. The subsequent strokes of a multi-stroke flash are displaced by the wind and give the appearance of a much wider channel - you can see the same effect on photographs.
One of my late Johannesburg colleagues and lightning researcher, Dr. David Proctor, told me a story about this years ago. A researcher moved from England to South Africa and commented that the lightning there was much thicker or wider than in Britain. David was skeptical, because we all now that channel width is a centimeter or two at most and should be the same everywhere. Then, on a European trip, David encountered a British thunderstorm. "The British lightning looked really thin and wimpy" compared to South African lightning, he confirmed. The only difference he noted was that in northern latitudes such as Britain, there are typically fewer strokes per flash than in more equatorial areas, such as South Africa. He postulated the difference in apparent size was due to the movement between strokes, with flashes of high multiplicity appearing much bigger than single-stroke flashes. Having viewed lightning in Britain, South Africa and the USA, I can confirm the apparent size difference and think David's explanation is likely correct.
Mike
And yet another consideration is the dynamic range of the detector used. If the lightning strike saturates pixels it’s hard to spot where the strike plasma ends and surrounding air begins.