A Proton Arc Over Lake Superior
Image Credit & Copyright:
Ken Williams
The setting had been picked out -- all that was needed was an aurora.
And late last August,
forecasts predicted
that an otherwise beautiful night sky would be lit up with
auroral green.
Jumping into his truck, the astrophotographer approached his secret site --
but only after a five hour drive across the rural
Upper Peninsula of Michigan.
What he didn't know was that his luck was just beginning.
While setting up for the image, a
proton arc -- a rare type of aurora -- appeared.
The red arc lasted only about 15 minutes, but that was long enough to capture in a 30-second exposure.
As the name indicates,
proton arcs
are caused not by
electrons but by more massive
protons that
bombard the Earth's atmosphere following an
energetic event on the Sun.
In the featured image,
the yellow lights on the horizon are the city lights of
Marquette,
Michigan,
USA.
The blue and yellow rocks in the
Lake Superior foreground are lit by a
LED flashlight.
Also captured, to the left of the red proton arc, was the band of our
Milky Way Galaxy.