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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
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Volcanic lightning pictured as Mount Shinmoedake volcano in Japan erupts
Remember the spectacular displays of magnetohydrodynamic lightning from the Icelandic volcano last year? Here is Japan's Mount Shinmoedake breathing sparks and fire:
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Patrick wrote ...
Are all those bolts appearing at once, or are there multiple exposures to make a single pic?
I wondered that myself, Patrick, but if you look at the second picture in the series, a single central ionization channel appears to fork out along the length of the volcanic plume, suggesting an event continuous in the time domain, perhaps in the decisecond regime.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
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The star trails in the second picture also suggest a single exposure of a couple of seconds, assuming a reasonably long telephoto lens was use to stay at a safe distance from the volcano.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
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If we look again at the first picture, it can be seen that the edges of the clouds of gas and dust to the lower right seem quite sharp to the camera, which would not be the case with a long time-elapse image in such a dynamic system.- a few seconds perhaps, but not much longer.
Most of the sparks link points of maximal potential difference separated by a dielectric gas, some ionisation channels being very short, and others much longer. If we could overlay a Schlieren image onto an ordinary photographic image of the lightning bolts, we might understand better the particular conditions which bring about so many points of high PD in the turbulent ejecta.
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Volcanic lightning pictured as Mount Shinmoedake volcano in Japan erupts: slide show
