Thursday, September 14, 2006

September 11th: 28 sprites from Mont Aigoual

Last Monday evening the Toulouse team, now assisted by Michal Ganot from Tel Aviv and her extra sprite camera (Watec 100N with 12mm f/0.8 lens) and GPS time inserter, arrived at the observatory on Mont Aigoual. We were a bit late as it was already dark when we arrived. Carl-Fredrik sms-ed us that Pic du Midi was cloudy. Our first camera (Watec 902H with 16mm f/1.4 lens) was set up and very soon captured a sprite amongst some clouds at 20:18 UTC. One hour later the camera recorded already 9 events, mainly groups of columns. The other camera was now running as well and used the time inserter. We had arranged the two to have some overlap on the sprites, for timing accuracy, and to cover a bit wider view.

column sprites dancing on visible lightning flashes:

The mesoscale convective system southeast of Bordeaux produced sprites in three periods since we observed: 20:18-21:49 UTC with 13 events (peaks near 20:50 and 21:20), 23:17-23:37 with 5 events, and 00:09-01:10 with 10 events. For 20 events we have accurate time stamps.

18 events were (more or less) purely column sprites, mostly in groups:

(this last one has long tendrils, these are not classic columns)

5 events contained carrot sprites, sometimes together with groups of columns:

2 events featured a big jellyfish (large tendrils, short bodies embedded in sprite halo):

and 3 events could not be classified easily (sometimes because of clouds):

In several cases the events contained multiple sprites separated by a few hundred milliseconds.

We left Mont Aigoual Wednesday afternoon, after a very foggy and later cloudy night with no chance of improvement.

The images are stacked output from UFOCapture, interlacing removed, black point contrast enhancement. Those of the Watec 100N with time inserter were captured with 640x480 resolution which apparently resulted in the grid pattern, only in the stacked images. Not all sprites are shown.


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