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Early morning sky on September 12, 2021, from Fairbanks, Alaska. I stayed up until 3 am last night waiting for aurora. Unfortunately, it stayed low on the horizon and never became very active. The above photo was taken right before I packed up the cameras and that green glow was not visible to the eye (article: Honesty in Aurora Photography). There was a brighter band on the horizon that was visible, but the trees were in the way for me.
The below photo was taken earlier, and you can see a faint light crisscrossing the Milky Way band. That purplish glow is known as STEVE or the Strong Thermal Emission Velocity Enhancement. It’s a pretty cool phenomenon that often occurs in the presence of auroras but isn’t actually an aurora itself. It is the result of supersonic ions flowing through the ionosphere. STEVE has been observed for a long time, but always was associate with auroras and thought to be a proton arc. It was only in 2018 that it was named and began to be studied as a separate entity. You can read more about it in this article from NASA: Aurora-Chasing Citizen Scientists Help Discover A New Feature of STEVE. STEVE was present from about 12:30-1 am AKDT this morning.