Proton Arc & Milky Way


Fazanavard فضانورد
Apr 5, 2015
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Aug. 19, 2015

A surprisingly strong G3-class geomagnetic storm erupted on Aug. 15th when a CME hit Earth's magnetic field. Two nights later, as the storm was subsiding, midnight sky watchers in North America witnessed a rare and beautiful form of aurora--a "proton arc." Paul Zizka photographed the phenomenon on Aug. 17th from Banff, Alberta:

"It was incredible," says Zizka. "The whitish pillar remained nearly stationary for over 30 minutes--enough time for a self-portrait."

In Val Marie, Saskatchewan, photographer Sherri Grant saw a purple proton arc cutting across the Milky Way. And in Oroville, Washington, at the Table Mountain Star Party, campers witnessed at least two more arcs.

Ordinary auroras are caused by electrons, which rain down on Earth's atmosphere from above. Atoms of oxygen and nitrogen, excited by the pitter-patter of electrons, form dynamic curtains of light. Protons have a different effect. For reasons not fully understood, protons normally trapped in our planet's ring current sometimes rain down on Earth's atmosphere during geomagnetic storms. En route, they excite a type of plasma wave called "EMIC"--short for electromagnetic ion cyclotron waves. The result is not a curtain, but rather a tight arc of light as shown above.

Many of the photographers who witnessed proton arcs on Aug. 17th have been observing auroras for years, yet they had never seen this phenomenon before. Geomagnetic storms still have the capacity to surprise!


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Taken by Sherri Grant on August 17, 2015 @ RM of Val Marie

Camera Used: Canon Canon EOS 7D Mark II
Exposure Time: 30/1
Aperture: f/2.8
ISO: 3200
Date Taken: 2015:08:17 11:20:58

Sony a6000 Rokinon 8mm f2.8 manual lens


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Taken by Sherri Grant on August 17, 2015 @ Just north east of Val Marie, Saskatchewan, Canada

Shot up in the western sky and intersected with the Milky Way. No other photos uploaded to website yet

These with Sony a6000 and Rokinon 8mm 2.8 lens. 30 sec exposure. ISO 2000

Proton Arc (and Aurora)


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Taken by Paul Zizka on August 17, 2015 @ Banff, Alberta

Camera Used: Canon Canon EOS 5D Mark III
Exposure Time: 50/1
Aperture: f/2.8
ISO: 2500
Date Taken: 2015:08:17 01:38:38

Here is what I think is a proton arc from last night. The aurora activity was overall pretty subdued, but that feature was incredible. The whitish pillar remained nearly stationary for over 30 minutes.

Self-portrait, Lake Minnewanka, Banff National Park, Alberta, Canada.


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Taken by John Zhou on August 16, 2015 @ Boundary Bay Regional Park, Tsawwassen, BC, Canada,

Camera Used: Unavailable Unavailable
Exposure Time: 10/1
Aperture: f/2.8
ISO: 1600
Date Taken: 2015:08:17 23:23:46

Here Im submitting an image taken from Boundary Bay Regional Park, Tsawwassen, BC, Canada, during a G3 geo-magnetic storm on Aug 16. What was captured is a rare occurrence of proton arc stretching horizon to horizon. The seemingly bluish tint probably makes it even rarer.


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Taken by Darrell Deewayne Price Jr. on August 16, 2015 @ Birch Bay, Washington

Camera Used: Canon Canon EOS DIGITAL REBEL XS
Exposure Time: 30/1
Aperture: f/3.5
ISO: 1600
Date Taken: 2015:08:16 01:24:21

Very bright beam of light visible to the naked eye stretching from northwest to southeast, very beautiful to see :)


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Taken by Dylan M on August 16, 2015 @ Oroville, Washington

On the last night of the Table Mountain Star Party on Eden Valley Ranch in north-central Washington state, a bright glow appeared in the North.

This soon broke out into a display of red pillars above the luminous green clouds. Meanwhile, two beams of light grew from the East and from the West, slowly rising and brightening until they met, crossing the Milky Way as bright as a searchlight.

For many at the star party, this spectacular display was their first view of the Aurora!

Nikon D610 24mm f/2.8
1: 30s at f/3.5 ISO 4000
2: 30s at f/3.2 ISO 4000
3: 15s at f/2.8 ISO 6400

Nikon D90 8mm f/3.5
4: 56s at f/3.5 ISO 1600


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Taken by John Nemy & Carol Legate on August 15, 2015 @ Island Stars Observatory, Hornby Island, BC, Canada

Camera Used: Canon Canon EOS 7D
Exposure Time: 15/1
Aperture: f/2.8
ISO: 5000
Date Taken: 2015:08:15 12:14:18

From western Canada this evening the aurora began very bright and then faded after 12:00 am. Still a very nice show.


Study of the proton arc spreading effect

13 July 2005

It has been well established that sometimes at some locations, precipitating protons can be a significant or dominant energy source to the ionosphere-thermosphere system [Sharber, 1981;Gussenhoven et al., 1987;Hardyet al., 1989]. It is crucial to consider the role of incident protons in addition to electrons in ionospheric disturbances at auroral latitudes [Galand and Richmond, 2001;Galand et al., 2001, and references therein]. Major difficulties in modeling proton precipitation arise because proton and hydrogen atom transport are coupled together through charge exchange and electron stripping collisions within the incident proton beam. These collision processes quickly convert the incident proton beam into a mixture of ions and neutrals. Energetic neutrals in the beam are able to travel across field lines until they are converted through collisions back into ions producing a spatial spreading effect unique to ion precipitation. The spatial spreading poses an additional difficulty for understanding the aeronomical effects of the ion precipitation.

Proton Arch During Aurora


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Taken by Raymond J Stinson, Astro-VIP Glacier on September 9, 2015 @ St Mary Visitor Center, Glacier National Park

Camera Used: Canon Canon EOS 60D
Exposure Time: 25/1
Aperture: f/2.8
ISO: 5000
Date Taken: 2015:09:10 00:14:28

Highly visible proton arch seen with Aurora on 9 September 2015. Canon 60D, Tokina 10-18mm f/2.8 lens, ISO 5000 with 20 second exposure.


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Taken by Jeff Hackenmueller on September 9, 2015 @ Almelund, Minnesota

Camera Used: SONY ILCE-7RM2
Exposure Time: 25/1
Aperture: f/1.0
ISO: 6400
Date Taken: 2015:12:11 23:05:53

I was shooting Aurora when this Proton Arc suddenly appeared!


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Taken by Skyler Casper on October 4, 2015 @ Seton Portage, British Columbia, Canada


In the corner of my eye I noticed something spanning across the entire sky, I noticed a long narrow beam of light stretch from mountain top to mountain top. Nowhere near the main action of the flickering streaks due north.

Canon Rebel t3i, 3.4/f, 3200 iso, 10s exp,
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