We flew again Sunday night / Monday morning, flight path above in green. The weather was marginal, but it went much better than expected. We got 9 or 10 sprites on the high speed, two of which were concurrent with the dSLR. This one - the best of the night - was on the final leg.
Most of what we saw were C-sprites, short for 'Column sprites' or 'Columnar sprites' - it just refers to their shape as tall, single columns. Here's a really good example of C-sprites:
And here are the same sprites in the high speed:
And here's another set, grouped in a ring called a crown:
With high speed video:
There's these strange groups of columns stuck together at the end like a bundle of sticks:
A less impressive / more noisy image:
And lastly, this sprite was pretty dim so I boosted the exposure pretty hard, and what popped out?
See the (faint!) green striations across the lower half of the image? Airglow! Never expected to get that in a three-quarter second exposure. It's a chemiluminescence - emission of light by chemical reaction - effect common across the world, but very dim and unnoticed by virtually everyone. The primary color is the same 557nm green line from the aurora, which indicates we're looking at the emissions from excited atomic oxygen, up above 100km altitude.
For this flight Geoff brought his own camera (D5100) aboard on a freshly purchased GorillaPod, to mimic my setup from last time on the opposite side of the aircraft. So now we have coverage on the left (science) side with my D7000 and a 'normal' 35mm lens, and coverage on the right (non-science) side with the D5100 and a wider 24mm lens. On the previous flight I burned through my 64Gb memory card really surprisingly quickly, so we brought 3 new 64Gb cards aboard (thanks Ryan!), for a total of 2x64Gb + 1x32Gb memory per camera, and we switched to shooting JPG fine rather than RAW images. This was a mistake: Once the JPG compression crunches the dark noise, I can't subtract it back out again. Fortunately I recognized we had memory to burn on the last leg and I switched back to RAW for the final data run, which is when I captured the best sprites.
As I write this, we've actually just finished flying another mission, our last of this campaign. But since it's 5 in the morning and I have to meet in 6 hours to remove the cameras from the aircraft then drive 13 hours, I'm going to save that update for later - when I have time to go through the 11,000 pictures (seriously!) and look for good sprites. I will say that I finally saw a sprite naked-eye; two of them, both recorded on Geoff's camera.