Friday, September 30, 2005

Sept 26 Sprites, as seen by the narrow FOV camera

Here are some close-ups of the September 26 sprites. Enjoy!

At 01:49 UT:

At 01:33 UT:

At 01:54 UT:

And my favourite at 03:23 UT:

You can magnify the images by clicking on them.


Blogger Jan Hemmer said...

Hello Agnes,

Beautiful pictures! So much detail is quite an achievement.
It makes me wonder even more about the physics behind these phenomena.
Is it realistic to consider sprites as a result of a positive CG-lightning or are they perhaps precursors of such a strike?
That is why I would like to know if the results of the eurosprite team is linked to other research such as lightning-detection?
If so, is the time-resolution of the data sufficient to answer the question of cause or effect?
Or is it possible to make an estimate of the energies involved by comparing your data with infra-sound measurements?

October 04, 2005 9:44 am  
Blogger Anna Odzimek said...

Dear Ian,
Sprites usually happen after a strong positivie CG+ discharge. I have just looked at the moments of the all campaign events (sprites) and Meteorage data (CG-discharges) and almost every event has its CG+ parent-lightning. As for comparison to infra-sound measurements I am not an expert but some people in the CAL project analyse such data in connection to sprites.
I am very impressed by your story about the thunderstorm and events of the night of 10/11 August. In fact we did observed ''something'' that night which was similar to sprite halos but we discussed it and we doubt they were real events at all. Maybe you could see such events that night? Please, if you could email me, I would send you one of the pictures of the doubtful events.

October 14, 2005 6:43 pm  
Blogger Oscar van der Velde said...

Hello Jan,

As Anna said, indeed there is a close connection between a positive cloud-to-ground flash. The key idea is that very large amounts of charge are drained to the ground. This creates an imbalance in the potential difference between thunderstorm and ionosphere that can accelerate electrons to the point that they can free other electrons when they hit atoms, which in turn accelerate, etc, which creates streamers of light as excited electrons fall back in lower energy trajectories around the atom core. With accurately timestamped video frames (GPS) one can obtain an accuracy of 20 ms if the video camera runs at 50 frames per second. Usually column sprites and elves occur then in the same frame as the flash, but carrot sprites usually are delayed due to a different mechanism of charge transfer, involving widespread in-cloud lightning processes - a paper of Agnes and me is to be submitted on this next week to a AGU journal.
Thanks for your great interest in our work!


October 14, 2005 7:17 pm  

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