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December 30 Auroras

Grand Rapids, MN

A high speed solar stream was affecting Earth, bringing auroras in the early morning.  The solar wind speeds looked quite fast (up to 700 km/s) with Bz slightly south, in the negative 3 to 5 nT range, so I ventured out to Pokegama Lake.  That's a location I usually choose when the moon is full because the city lights really impact the view otherwise.  When there's a bright moon, the city lights get washed out, and if the auroras are bright, they'll stand out against the moonlight, too.

When I'm trying to anticipate a good show, I'll look for a plain auroral arc to the north, stretching from the northwestern horizon to the northeastern horizon. These arcs are usually very subtle and not easily recognized unless you know what to look for. A persistent arc is usually a harbinger of an auroral substorm, and one of these was indeed on the way. It was time to set up a time lapse and be prepared to change my camera settings quickly for the substorm. Those usually start in a matter of seconds.

Pokegama Auroras
A faint aurora oval appears over Pokegama Lake.
Pokegama Auroras
A substorm erupts at 11:34 PM as the auroras retreat closer to the horizon.
Pokegama Auroras
An auroranado forms on the right at 11:38 PM.
Pokegama Auroras
Occasional bright blotches and tall columns at 11:44 PM.
Pokegama Auroras
A crop from the earlier view at 11:52 PM.  The plume on the right is the Blandin Paper Mill.
Pokegama Auroras
The auroras start to dim by 12:07 AM.

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