Possible Proton Arc
Taken by Lauri Kangas on July 29, 2016 @ Fort Frances, Ontario, Canada
Click photo for larger image
  Camera Used: Canon Canon EOS 6D
Exposure Time: 13/1
Aperture: f/1.6
ISO: 2500
Date Taken: 2016:07:29 01:26:19
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During the last two nights there has been some minor aurora activity (Kp=4) in northwestern Ontario. Tonight just after midnight I noticed a spike growing in the NW sky. It kept getting taller and I had to move my camera into portrait mode to capture the size of the entire arc. This might be a proton arc but the definition of this phenomenon is unclear to me. Regardless, it was really cool. It almost looked like a green and purple braid in some photos. I tried to capture it as it grew closer to the Milky Way, but my 20mm lens with full size DSLR image sensor could not completely capture both the arc and the Milky Way.
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It sure seems to be a bonafide proton arc! Based on other photos of the phenomenon. It is well separated from the other aurora activity, and its continuous length leave little doubt. Nice catch! To get both the proton arc and the Milky Way, maybe a stitch of several exposures would have worked? Might be a little harder to do with longer exposures.
Posted by oregonrandy 2016-07-29 11:51:51
Thanks oregonrandy. I was too far from the house to get my 8mm Sigma fisheye which would have captured a full sky image. The arc was evolving and moving too fast for stitching. Ive been doing some research and Im not convinced this is a proton arc. Maybe just a strong detached auroral arc? I did find this post that seems legit:

Posted by LaKangas 2016-07-29 14:39:04
34 thumbs up
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