Updated: Nov 12
At the end of our first Nature Photography Academy photography workshop, we spent a great weekend putting everything we learned into practice. On the final night (Sunday, November 5), we were shooting star trails when a strange and mysterious red glow appeared in our pictures.
Was it the glow from a city? Nope. There was nothing in that direction.
Was it the glow from a distant wind farm? No, on that idea as well, because the glowing feature was too big.
What was it?
"I think it's the aurora," I say. I remember seeing the aurora in North Texas in the late 80s after a huge geomagnetic storm, which looked the same.
All of the data looked like it could be the aurora. There was a robust geomagnetic storm, which pushed the KP indices into the 6 to 7 range. When the KP Index gets that high, it's not unusual to see the aurora borealis glow in the southern latitudes. So, I thought we were likely looking at the aurora.
Thanks to some crack detective work by one of our Academy participants, Anita found out that the glow wasn't an aurora but a rare phenomenon called a SAR arc.
According to spaceweather.com, "During this past weekend's strong G3-class geomagnetic storm, low-latitude auroras spread as far south as Texas and Arizona. Upon further review, most of those lights were not auroras at all... SAR arcs were discovered in 1956 at the beginning of the Space Age. Researchers didn't know what they were and unwittingly gave them a misleading name: "Stable Auroral Red arcs" or SAR arcs. In fact, SAR arcs are neither stable nor auroras.
Auroras appear when charged particles rain down from space, hitting the atmosphere and causing it to glow. SAR arcs form differently. They are a sign of heat energy leaking into the upper atmosphere from Earth's ring current system–a donut-shaped circuit carrying millions of amps around our planet."