APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

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APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by APOD Robot » Mon Aug 03, 2015 4:10 am

Image A Proton Arc Over Lake Superior

Explanation: 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.

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by Frank Rosser » Mon Aug 03, 2015 5:04 am

Are "proton arcs" actually visible to the unaided eye?

I have never been able to find a answer to that question.

My feeling is the visible proton arcs are not caused by proton precipitation but by regular electron precipitation.

The research I have read suggests arcs caused by proton precipitation are diffuse and tend to create light that cannot be seen by the unaided eye.

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by geckzilla » Mon Aug 03, 2015 5:26 am

Frank Rosser wrote:Are "proton arcs" actually visible to the unaided eye?

I have never been able to find a answer to that question.

My feeling is the visible proton arcs are not caused by proton precipitation but by regular electron precipitation.

The research I have read suggests arcs caused by proton precipitation are diffuse and tend to create light that cannot be seen by the unaided eye.
What research is that? It seems clear to me that this particular arc was visible to the photographer's eyes, at least as a dim streak if not a visibly red one.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by Beyond » Mon Aug 03, 2015 9:00 am

Frank Rosser wrote:Are "proton arcs" actually visible to the unaided eye?

I have never been able to find a answer to that question.

My feeling is the visible proton arcs are not caused by proton precipitation but by regular electron precipitation.

The research I have read suggests arcs caused by proton precipitation are diffuse and tend to create light that cannot be seen by the unaided eye.
Here, it says this one was clearly visible to the naked eye.
http://spaceweathergallery.com/indiv_up ... _id=101070
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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by geckzilla » Mon Aug 03, 2015 11:19 am

Geo wrote:So much for "secret site"! :)

https://en.wikipedia.org/wiki/Marquette ... te,_MI.jpg
Doesn't look like the same spot to me.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by Boomer12k » Mon Aug 03, 2015 12:31 pm

So Awesome!!!

Well...it reminds me of a Bow Shock of some nebula...

:---[===] *

PS...doesn't look like the same spot to me either....

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by Dad is watching » Mon Aug 03, 2015 1:43 pm

The energetic event on the sun ejected a stream but is the stream all protons or is it just proton rich? And would that ejected matter come from a lower level of the sun?

When it gets to the Earth, we assume that our magnetic field directs it the same way that electrons are directed. Do the protons, being heavier, interact with lower levels of our atmosphere resulting in the different color? Or do both protons and electrons interact with our atmosphere at similar altitudes?

Is this the same as the 'red aurora' that appears in photos of aurora taken from the shuttle; that appears to cap regular green aurora that seems to decent lower into the atmosphere?

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by neufer » Mon Aug 03, 2015 3:16 pm

Dad is watching wrote:
The energetic event on the sun ejected a stream but is the stream all protons or is it just proton rich?
And would that ejected matter come from a lower level of the sun?
  • Think about the normal aurora as coming from the outer Van Allen belt
    while lower latitude proton arcs come from the inner Van Allen belt
https://en.wikipedia.org/wiki/Van_Allen_radiation_belt#Inner_belt wrote: <<While electrons (of different energy levels) inhabit both the outer and inner [Van Allen] belts, high-energy protons characterize the inner belt. The inner Van Allen Belt extends typically from an altitude of 0.2 to 2 Earth radii or 1,000 km to 6,000 km above the Earth. In certain cases when solar activity is stronger or in geographical areas such as the South Atlantic Anomaly (SAA), the inner boundary may go down to roughly 200 kilometers above the Earth's surface.

The inner belt contains high concentrations of electrons in the range of hundreds of keV and energetic protons with energies exceeding 100 MeV, trapped by the strong (relative to the outer belts) magnetic fields in the region.

It is believed that proton energies exceeding 50 MeV in the lower belts at lower altitudes are the result of the beta decay of neutrons created by cosmic ray collisions with nuclei of the upper atmosphere. The source of lower energy protons is believed to be proton diffusion due to changes in the magnetic field during geomagnetic storms.>>
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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by Ron-Astro Pharmacist » Mon Aug 03, 2015 9:16 pm

Turbulent weather, above and below the clouds, make conditions dangerous for those that choose to work amidst the waves. Thanks for the "Superior" link. It's good to remember those who pay the ultimate price to supply us with the sustenance needed, both mentally and physically, to live our lives. "The Great Sea" sustained the Chippewa as the sun sustains us all; but not without a price. :cry:

Today's APOD reflects that effort nicely in the blue, yellow and green of Michigans' colors
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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by neufer » Mon Aug 03, 2015 10:08 pm

Ron-Astro Pharmacist wrote:
Turbulent weather, above and below the clouds, make conditions dangerous for those that choose to work amidst the waves. Thanks for the "Superior" link. It's good to remember those who pay the ultimate price to supply us with the sustenance needed, both mentally and physically, to live our lives. "The Great Sea" sustained the Chippewa as the sun sustains us all; but not without a price. :cry:
https://en.wikipedia.org/wiki/Great_Lakes#Name_origins wrote:
Lake Superior: English translation of French term lac supérieur (upper lake), referring to its position north of Lake Huron. The indigenous Ojibwe call it gichi gumi (from Ojibwe gichi big, large, great; gumi water, lake, sea. Popularized in French-influenced transliteration as Gitchigumi as in Gordon Lightfoot's 1976 story song, The Wreck of the Edmund Fitzgerald, or Gitchee Gumee as in Henry Wadsworth Longfellow's 1855 epic poem, The Song of Hiawatha).
Click to play embedded YouTube video.
  • By the shore of Gitche Gumee,
    By the shining Big-Sea-Water,
    At the doorway of his wigwam,
    In the pleasant Summer morning,
    Hiawatha stood and waited.
    All the air was full of freshness,
    All the earth was bright and joyous,
    And before him, through the sunshine,
    Westward toward the neighboring forest
    Passed in golden swarms the Ahmo,
    Passed the bees, the honey-makers,
    Burning, singing in the sunshine.
    Bright above him shone the heavens,
    Level spread the lake before him;
    From its bosom leaped the sturgeon,
    Sparkling, flashing in the sunshine;
    On its margin the great forest
    Stood reflected in the water,
    Every tree-top had its shadow,
    Motionless beneath the water.
Art Neuendorffer

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by Guest » Tue Aug 04, 2015 12:02 pm

Boomer12k wrote:So Awesome!!!

Well...it reminds me of a Bow Shock of some nebula...

:---[===] *

PS...doesn't look like the same spot to me either....

I would suggest upgrading your monitors then, or glasses....

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Re: APOD: A Proton Arc Over Lake Superior (2015 Aug 03)

Post by alter-ego » Wed Aug 05, 2015 4:36 am

geckzilla wrote:
Geo wrote:So much for "secret site"! :)

https://en.wikipedia.org/wiki/Marquette ... te,_MI.jpg
Doesn't look like the same spot to me.
Yeah, it not only doesn't look like the same spot, it's totally in the wrong direction. Presque Isle Park is north of Marquette but the proton arc runs right thru Hercules head (directly over Marquette). That puts the view heading just north of west from the photographer's location, therefore the location is basically east of Marquette. The best candidate I can find is on the coastline roughly midway in longitude between Au Train and Christmas, about 30 miles away from Marquette.
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