August 31, 2017 Auroras
Chippewa National Forest
A corotating interaction region ahead of a coronal hole high speed stream of solar wind was on the way. I had been watching the solar wind conditions most of the evening, but I was not impressed with the magnetic fields, so I decided to call it a night. Of course, one last check of Bz before I closed my eyes revealed that it had suddenly dropped to -19 nT. If it stayed that low, it would bring quite a show, but I went to sleep anyway. Since the conditions had been quiet for a couple days, I figured it would take a while for the auroras to get revved up. I set my alarm clock for 3:00 AM.
I did not sleep that long. About 20 minutes before the alarm clock would go off, I awoke, looked at the solar wind conditions again, and decided I should get out. The moon was on its way below the horizon, so the sky conditions would be good for shooting, or so I thought.
I drove north and could see the band of auroras ahead of me as I proceeded into the Chippewa National Forest. When I got to Pughole Lake, I got out of the car to discover I had driven toward a band of low clouds. I checked satellite and found it was a fairly small patch of clouds, and they'd move off soon. Above them, though, I could see that the stars and the auroras looked a bit dim. There was a fair bit of smoke in the sky.
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| A substorm begins on Pughole Lake. |
The pictures don't look particularly smoky, but I had to double the exposure time on my shots compared to what I usually use. I took pictures of a mild substorm and then pondered when I should return home and get a couple hours more sleep before work. I'm usually out photographing earlier in the night, and because of my late timing this time, I was photographing while the Suomi NPP polar orbiting satellite was flying overhead. This allowed me to make a comparison between what I saw at ground level and what the satellite was seeing from above.
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| A Suomi NPP satellite flyover occurred while I was taking pictures. |
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| Picture of the auroras at the same time as the satellite image above (24mm focal length, camera 1). |
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| Picture of the auroras at the same time as the satellite image above (24mm focal length, camera 2). |
My images correspond reasonably well with the satellite picture. The base of the auroras was about 10 degrees, maybe a little more, above the horizon, and that would mean they were about 350 to 500 km to my north. I thought that would I saw on the ground would look a little narrower on satellite. This was the same way the comparison struck me on July 15, 2012.
Anyway, I continued to take a few more pictures and made it to bed a little after 5:00 am, allowing me to get a couple hours sleep before heading to work.
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| Auroras expanded over the entire northern sky. |