June 23, 2015 Auroras
Itasca County, Minnesota
Wow! This was one of the best aurora displays of this solar cycle, in part because of the timing of the period of most prolonged, negative Bz, and partly because of the strength of the geomagnetic storm: 8 on a scale of 9, which ties it for the strongest of Solar Cycle 24. We are still waiting for a storm with a strength of 9 on that scale. It has been a very weak cycle according to the standard since 1900.
Bz had dropped to nearly -40 nT right after the initial shock from the CME came past the ACE satellite, but then Bz went positive for most of the rest of the afternoon. I was not expecting much. However, around suppertime, it dropped back down into the -20s. That was enough to bring the auroral oval overhead and even, perhaps, bring the auroras into the southern sky. It was not nearly dark yet, but if the auroras behaved as predicted, I knew I'd be able to see them overhead almost as soon as the stars appeared. I drove north on Highway 38, and that's indeed what happened.
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| Auroras overhead, east, and south! |
I continued north to Pughole Lake because there was a nice view to the east and south from the boat landing. However, that landing was occupied by somebody just sitting in their pickup-- just sitting there doing nothing. Just weird, if not irritating. I did get out and snap a few pictures, and seeing that the pickup occupant did not respond (maybe he could have looked up in the sky), I just got irritated and left. I almost never encounter anybody after sunset at any shooting location.
I decided to use that weirdness as an opportunity to try a new shooting location. I had thought about Little Long Lake to the east of Highway 38. That lake was much narrower than Pughole, but it had an east-facing boat landing, which would afford me a view of the eastern and southern sky, in addition to the more typically viewed northern sky. I set up the tripod and started shooting. As the sky continued to darken, the dimming revealed an auroral band that was right across the sky from the eastern to the western horizon.
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| The main auroral arc is overhead. Tonights auroras will put on a nice show! |
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| I typically use 24mm as a focal length, but that was too narrow tonight. |
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| Auroras are overhead while a more colorful band begins in the northen sky (left). |
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| The bright colors spread around the sky. |
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| When the auroras cleared overhead, more color was revealed closer to the horizon. |
