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May 12, 2015 Auroras
Grand Rapids, MN
A corotating interaction region and high speed stream of solar wind impacted Earth, bringing a strengthening magnetic field and southward Bz, followed by increasing solar wind speeds. The Grand Rapids had increasing cirrus and cirrostratus clouds ahead of an upper level trough that would give us some rain the next day, so I wasn't thinking the viewing conditions were going to be very good. The high resolution numerical models showed a break in the clouds in the mid to late evening, which would give us an opportunity for viewing, but I did not trust that due to the small size of the break.
Lo and behold, the clouds did clear, and I walked outside the house and looked to the north to see a glow in the northern sky. I quickly packed up the camera equipment and drove over to the north side of town. I always stop at the closest possible good viewing location, and that was McKinney Lake. I stood there for a few minutes and snapped one or two pictures of a partially obscured green band. Then, there was an eruption of magenta.
Color erupts at McKinney Lake.
McKinney Lake can feel too disruptive because of the number of cars coming up Highway 38. The road is oriented so that car headlights point right into the boat landing until the road curves away in the last block before the landing. Since the road is to the south and my camera is pointed north, this usually isn't a problem until the cattails grow tall and get illuminated unevenly. I guess just I don't enjoy being illuminated by car headlights while shooting northern lights. Time to head to quieter location. With my typical lazy self, I headed to the next closest site, which is Peterson Road.
Auroras reflected in the trail in the bog.
The wind was really calm, so I really needed to be shooting over a lake somewhere. Again, I'm lazy. I didn't go back to McKinney Lake, but Prairie Lake was almost as close at this point.
Prairie Lake has some color, and the water is like glass!
This ended up being a great shooting location, but I'm always wondering if I might find some really great foreground on a different lake where I've never shot before. I could not think of such a location, there was a threat of clouds, and the lazy feeling continued to overtake me, so I stayed put. The auroras continued to expand and fill the sky.
Wider shot at 16 mm.
More reflections off the lake.
Enjoying the show.
Looking northeast.
Looking northwest.
Looking north. This is actually from a 15mm fisheye lens, but Adobe's automatic lens correction makes it look interesting in rectilinear form.
Dam reflections.
Here's a fisheye shot (still in fisheye form) looking straight up.
Looking high in the southern sky with the 24 mm lens. I'm starting to get "aurora neck".
Here are a couple images of solar wind data during the event. There was an increase in proton flux, which typically signals an oncoming CME, but when the supposed impact occurs, the magnetic field strength dropped quite a bit. The aurora show really occurred before this, and the solar wind data show more of a corotating interaction region (high density, strong magnetic field) followed by decreasing field strength and faster wind speeds.
Low energy proton flux increases ahead of a CME and then drops. If there was a CME, it actually brought less favorable conditions for auroras.
Solar wind data. Before the show got going, magnetic field strength increased, Bz dropped south, and the wind speed and temperature started to increase. After about 0900 UTC on the 13th, magnetic field strength suddenly dropped while wind speeds approached 800 km/s.
