January 14, 2018 Auroras

Wabana Lake, Itasca County, Minnesota

A high speed stream of solar wind reached Earth earlier in the data, and a few hours of southward Bz (solar wind magnetic field) brought unsettled geomagnetic conditions.  It was a no-moon night, so I decided a trip north of town, to get clear of city lights, would be in order.  That said, I was still able to see the lights from International Falls, 130 km (80 miles) to the north.  The haze from city lights seems to be more visible during the winter, probably due to the snow cover reflecting the light from street lamps upward.

On my drive north, I glared at the northern horizon looking for the signature arc of faint light.  I saw it when I got to the northern city limits of Grand Rapids, and there appeared to be a patch of aurora a bit higher in the sky.  The main arc was pretty low to the horizon, but it looked good enough that a trip to Wabana Lake was warranted (it's about fifteen minutes longer than the easier drives I take to the north side of town).  This extra fifteen minutes is plenty of time for things to change.  Perhaps, as I was driving, the solar wind magnetic field was becoming northward, or maybe I'd miss a good substorm.

Thanks to colder than average weather to this point in the winter, the ice was pretty thick for this time of year, so I drove out onto the lake from the landing.  I looked to the north and initially could not see any lights through the trees so I thought they might have fizzled out, but when I cleared the peninsula and could see the entire sky, the faint arc was there, right along the horizon.  The temperature was a balmy -25 deg F (-31.5 deg C), and the wind was calm.  The exhaust from the Jeep hung in the air and did not move.  It was an arctic style evening. I parked the car off the main ice road and reached for my camera gear.

The moment I did, the arc started to brighten.  I hastened my deployment of gear and started shooting right before the auroral columns began to appear.  It seems that happens a fair bit.  The substorm starts right as I start shooting, like I got there just in time (other times, I have missed the first substorm of the evening).

The first, bright, dancing auroras of the evening.

The lights quickly dimmed again, and there was just a dull glow on the horizon. It was much dimmer than the lights of Grand Rapids to my south and a little dimmer than the Iron Range cities to my southeast and east and Bemidji to the west. I could also pick out the lights of International Falls to the north, although that required waiting for the auroral arc to rise above the northern horizon, which it eventually did. I checked Bz again and saw that it was -8 nT, so that might have explained why the auroral oval was drifting southward and moving higher into my line of sight. I waited patiently for another substorm to begin, but the lights continued to dim, almost fading out entirely. Despite the dimming, the arc was holding its position above the horizon and not retreating into the horizon.

By the time things brightened again, I needed to run around in circles to stay warm in the sinking temperatures. I had actually left the camera inside its bag until something more interesting began, and fortunately (due to my running in circles), my fingers were warm enough that I could feel the camera as I put it back on the tripod. Rather than a big, fast flame-out type of substorm, there was a general brightening with a bit more mellow, slowly evolving structure for about an hour. There were not any really tall columns, but there was a bit of red on top of the green. I shot until the structure and brightness both faded. I had a busy enough schedule the next day that I wanted to get to bed. Also, the clouds were thickening and would continue to do so through the rest of the night. I considered it a success to see a decent show in January. That does not always happen.

A second substorm begins.

A few seconds later, cropped.

Some reds appear.

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