19 August 1991: Ottumwa, Iowa

I was home for a couple weeks before heading out to Wyoming for graduate school, and happened to catch this one a few days before leaving. In retrospect, I'm not 100% certain that this is the best display I've ever seen, but it was certainly the most dynamic.

I have two written accounts of this spectacular display, expressed in local time, UT minus 5 hours. The first is the raw record that I typed into my computer as I would run inside periodically:

2:30am very bright green glow, became the brightest that I have seen, could see arc, extremely bright in NNW with generally 3-4 rays that reached as high as 60 degrees, the arc was at 20 degrees, much higher that other great display, the rays weren't particularly bright, but well defined, could see left to right motion in rays and in the dozens of black lines in the arc

3:15am has faded quite a bit, the arc is more diffuse and fainter, still moderately bright, the arc had been sharply defined before, there are a couple of faint difuse rays

4:00am band very bright again with one good 60 degrees ray, another bright patch very low in N, may be part of arc

[x:xxam] spectacular display 4-6 rays with 4 converging to N up to 70-80 degrees and one of them to zenith, hints of a rose color, then frequent pulsations along horizontal lines from 20-50 degrees, could see some upward motion with those, during this the whole thing got more diffuse, then a very bright ray due N went to zenith and maybe slightly beyond, the green glow part is very large but only moderately bright, at 4:25 as I came in, a bright ray has formed NE (this has been a wide display), with old rays making a diffuse pillar up to zenith due N, best display ever

By 4:50am has fizzled to faint glow with a couple of faint 60 degree rays.

I wrote a more coherent report about this aurora later in the day for an e-mail to a friend:

There was a spectacular auroral display last night (morning of the 19th). At around 2:10am I went outside and even before my eyes had dark-adapted any I noticed a very bright green glow to the north. By 2:30 the glow had become a complete band stretching from NE to NW with the band curving below and 'behind' the NW part, forming an arc. The region around the curve in the arc was stunningly bright, because of the layering effect created by the arc. Generally there were 3-4 moderately bright, distinct rays that reached as high as 60 degrees, the band itself was at about 20. The band was considerably brighter that the green parts in the auroral photos of mine that I showed you. I could see slow left to right motion in the rays and in the dozens of thin dark spikes that could be seen in the band.

By 3:15 it had faded quite a bit, with everything more diffuse and fainter. At 4:00 I checked again and the band had brightened again with one good 60 degree ray, and a detached bright part of the arc very low in the NNW. A few minutes later the real show began. There were generally 5-7 rays along the band, with 4 of them converging from right around due N to about 70-80 degrees above the horizon with one of them reaching zenith. From an altitude of about 45 degrees on up, the rays had a slight rose tint. The red color was never nearly as vivid as it had been in the display that I photographed. Then, amongst these rays from about 20-50 degrees altitude there appeared frequent pulsations along horizonal lines. These are very hard to describe but were similar to a tesla coil, with the horizonal sparks moving up. In the aurora each of the bands only lasted for about a half a second, but an upward movement on the bands of a degree or so was noticable. The bands were not particularly bright but VERY impressive as I had never seen them before this morning. Interestingly enough during the 5 minutes or so that the bands occurred, the rest of the display got much more diffuse with the rays right around north making a 40 degree wide pillar of moderate brightness stretching up to about 60 degrees. The final major spectacle in the display was a very bright narrow ray that developed due N through Polaris and up slightly past zenith. A few minutes later at 4:25 the Polaris ray had faded to blend in with the pillar and extend it to near zenith with another good ray forming due NE, which is as far away from N that I have seen a ray; you really can see the perspective effect of convergence with a ray that far from north.

By 4:50 the display had fizzled to a faint glow and very faint diffuse rays Although this display didn't have the vivid color variations that the other major display that I saw, I think overall this was the best.


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