Aurora Borealis
 | Author:
Jeff Ross
Contributor |
On July 22, a relatively rare event for us began just before midnight. It was a pretty good display of Aurora Borealis, the Northern Lights.
Aurora Borealis is the culmination of a series of events that start on the surface of our local star. On July 20 at 7:10 pm, sunspot complex AR3060 exploded on the surface of the Sun, sending a solar flare and a Coronal Mass Ejection into space. The flare was rated as a Type-II solar radio burst and caused shortwave radio blackouts on Earth about 10 minutes later.
A Type-II burst is not very big but the CME fol¬lowing it was directly aimed at Earth. A Coronal Mass Ejection is a bundle of super-charged plasma and a strong magnetic field and travels much slower than light. Observations showed this CME leaving the Sun at 2.4 million miles an hour. The Earth is, on average, 93 million miles from the Sun so a forecast for a smallish auroral display could possibly start on late July 22 or early July 23.
Possibly is the key word there. Not all Earth di¬rected CMEs result in an auroral display. Sometimes the CME's magnetic field dissipates before hitting the Earth. Sometimes the CME will strike a glancing blow off our magnetic field and bounce away from Earth instead of being directed down.
And sometimes, as on July 22 and into the early morning on July 23, it all works. The energy from that plasma causes oxygen and sometimes nitrogen to ionize, releasing the light that makes up an auroral display. Ionized nitrogen releases a reddish light, ionized oxygen glows green. This aurora had both.
I did not actually see this aurora! I was up around 1:00 am on July 23 but didn't see anything at all in the north. However, the entire display was captured using a small computer driven super sensitive camera. My Aurora Cam is an ongoing project to first capture aurora in real-time, and second, send an alert out via text message when a display is detected. The alerting process is still prone to far too many false alarms but the capturing part is working well.
More details about this project and the resulting movie can be viewed at https://www.starhouse-observatory. org/aurora_cam.html. Aurora is first visible in the movie just before midnight on July 22 and continues until around 2:30 am on July 23.
Our Sun is about in the middle of its 12-year solar activity cycle. With solar activity higher than we've seen for a few years, we can hope to see more auroral displays like this one soon.
With clear skies, of course.
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PhotoCredit: Jeff Ross
Image 1 Caption: Aurora Borealis
