September 28, 2017 Auroras
Ames, Iowa
This marks the farthest south I've ever shot auroras. I was at a wind energy symposium at Iowa State, so I was away from home. When the auroras arrived, the location I chose northeast of town was at 42.07 degrees north, which is more than five degrees south of my home town. Since the auroras are based at such a high altitude, they cam be visible from over 1000 km away if the sky conditions are right. During this particular event, the southern extent of the auroras reached overhead in northern Minnesota. For Ames, this meant the tops of the auroras reaching as much as 20 degrees above the horizon.
The auroras were caused by a high speed stream of solar wind, reaching 700 km/s while Bz was still pretty far south (-10 nT). Normally, the magnetic fields weaken when the high speed stream sets in, but this night was somewhat of an exception. The corotating interaction region had gone by Earth in the early morning hours of the 27, but strong magnetic field continued for a while, even when the solar wind speed picked up.
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| Auroras view from a point a few miles east/n0rtheast of Ames, Iowa. |