September 2, 2016 Auroras

Chippewa National Forest, Itasca County, MN

Solar wind conditions were looking good during the evening for an appearance of the auroras right at twilight. A high speed stream of solar wind had arrived, and Bz was south around -8 nT with wind speeds around 600 km/s.  Normally, a Bz of -8 nT doesn't bring about a particularly interesting display, but September is peak season for the auroras, and conditions that would not prompt much of a display in mid summer or mid winter can bring a dazzling show around the fall equinox.

I took care of my evening chores and headed out north out of town as soon as I could.  I decided to check out Caribou Lake as a shooting location because I had not been there before.  I found my way to the landing as twilight had not yet faded much.  I hopped out of the car to check the view to the north.  Unfortunately, I could not see the Big Dipper or tell which star was the North Star because the view directly the the north was blocked by trees along the shoreline.  I scanned the horizon to see if there was anything popping out.  It was still too bright to the north to see auroras, but as I looked to the east, I could see a bright spot.  I stared at that spot for a bit to see if it was moving as an aurora would or if it was a cloud.

After only a second or two, it was clear that it could be the beginning of an auroral substorm.  I dashed back to the car, grabbed a camera and tripod, and set it up at the edge of the water, pointing northeast.  The sky exploded in auroras, but the twilight was still pretty bright.

Auroral columns begin to puncture the arc as twilight fades.

The auroras really intensify and begin to fill more of the sky.

As the show continued to intensify, I got a friendly text from someone who was also watching the show to remember to look south. Indeed, there was a narrow ribbon of auroras that had formed overhead and a little to the south. I switched to a fisheye lens on my time lapse camera and dashed back to the car to get a second camera.

I decided to switch to a fisheye lens.  This is Adobe Camera Raw's "correction" to make it nearly rectilinear.

With my other camera, I spent time photographing the display overhead.

When this more southern display faded, I looked back north and saw that the auroras had faded rather quickly. It seemed a little odd that things had quieted down so quickly, but the sky was now mostly dark, partly due to the disappearance of twilight, but also due to the fading auroras. A few columns persisted to my southeast, but the show had mostly ended. I debated my next options and decided it was time to switch to a lake with a better northern view because the auroras had retreated to the horizon. By the time I left Caribou Lake, and auroral arc was re-forming across the northern horizon.

I arrived rather quickly at North Star Lake, which was not really far from my first shooting location. I set up and too pictures right away, expecting the auroras would develop and intensify into a substorm, but that never happened. They did come a bit closer from the northern horizon, but then they soon faded, even when Bz turned back south again. Normally, a second substorm would occur, but for some reason, that did not happen tonight. I shot for a bit longer then decided to head home.

Suddenly, I noticed the auroras had greatly dimmed.  At least the twilight was gone, so I could have better contrast for the next round.

A few columns persisted to my east-southeast.

A new lake and a rebuilding auroral arc. For some reason, this never reached the substorm phase and soon faded.

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