18 Green Aurora Photos from Norway, Iceland, Canada, Alaska and the ISS

Green is the signature colour of the aurora, and these 18 photographs show it from two very different places: the snowy ground of Norway, Iceland, Sweden, Canada and Alaska, and the International Space Station, 400 km above the planet. Taken between 2005 and 2015 by photographers, scientists and astronauts, they were gathered around St Patrick’s Day, when green fills the calendar.

The first frame was shot near Tromsø, in Arctic Norway, on 9 January 2014 by Harald Albrigtsen, and was featured by NASA alongside its coverage of the Sun’s first X-class flare of 2014. From there the selection moves between ground and orbit, so the same glow appears as a curtain over a fjord in one image and as a luminous ribbon wrapped around the curve of Earth in the next.

Why auroras glow green

Auroras start with the Sun. Fast streams of solar wind from coronal holes, and the larger clouds of plasma thrown out in coronal mass ejections, disturb Earth’s magnetosphere. That pushes electrons and protons down into the upper atmosphere, where they collide with oxygen and nitrogen and make them emit light.

• Green (557.7 nm): atomic oxygen at around 100 km and above. This is the brightest and most common auroral colour, which is why green dominates the photographs here.
• Red (630 nm): also oxygen, but higher up, where the air is so thin that atoms have time to release red light before colliding.
• Blue and purple: nitrogen, lowest in the display, often seen on the fringes of bright curtains.

The name comes from Aurora, the Roman goddess of dawn. Galileo used the word for the lights in 1619, and Pierre Gassendi’s description of a 1621 display helped fix the term “aurora borealis”. In the south the same phenomenon is called aurora australis.

Green auroras from the ground: Norway, Iceland, Sweden, Canada and Alaska

Ground photographers anchor the light to a place. Snowy peaks, forest silhouettes and still lakes give scale to curtains that may stretch hundreds of kilometres. The ground images include:

• Fáskrúðsfjörður, east Iceland, 8 March 2012, photographed by Jónína Óskarsdóttir.
• The Alberta prairies east of Edmonton, Canada, where Zoltan Kenwell caught a display driven by a high-speed solar wind stream in spring 2011.
• Venetie, Alaska, 3 March 2014, when NASA launched its GREECE sounding rocket from Poker Flat Research Range into the aurora to study the curls that form in auroral curtains. Christopher Perry took the photograph.
• Swedish Lapland, 25 January 2012, by Peter Rosén.
• Whitehorse, Yukon, on 31 August and 1 October 2012, the first a lakeside reflection by David Cartier Sr.
• Bear Lake, Alaska, 18 January 2005, by U.S. Air Force Senior Airman Joshua Strang.

Auroras seen from the International Space Station

The ISS orbits at about 400 km, circling Earth 15.5 times a day on a track that reaches 51.6° north and south. Auroral light is emitted mostly between about 100 km and a few hundred kilometres up, so astronauts often look down on the display, or skim right through its upper edge. ESA astronaut Alexander Gerst posted his 29 August 2014 image saying words could not describe how it felt flying through an aurora.

The orbital frames span nearly five years, from May 2010 to Terry Virts’s moonlit view of Ireland, the United Kingdom and Scandinavia on 6 February 2015, during Expedition 42. ESA’s Samantha Cristoforetti contributed the frame from 9 December 2014.

Where and when to see green auroras

Auroras are most frequent in the auroral oval, a band roughly 660 km wide centred near 67° magnetic latitude in both hemispheres. That puts northern Norway, Iceland, Swedish and Finnish Lapland, Alaska, Yukon and the Northwest Territories right underneath it.

• Season: you need darkness, so the Arctic summer with its midnight sun is out. The long nights from autumn to early spring are the time to go, and geomagnetic storms tend to be more frequent around the equinoxes.
• Solar cycle: large storms are most common near the peak of the Sun’s 11-year cycle and in the few years after it.
• Forecasts: watch the Kp index. Around Kp 3 is quiet; values approaching 9 mean a major storm that can push auroras far south of the oval.

Dress for a long wait outdoors in Arctic cold. Many of the best displays arrive in bursts called substorms, which can brighten the sky within minutes.

Related reading

• Harald Albrigtsen’s whales and northern lights
• ISS Symphony: a timelapse from the International Space Station
• Ronn Murray’s Real-Time Aurora Film Near Fairbanks, January 2015
• Aurora Borealis in Real Time: Watch the Northern Lights Change Shape
• Kaspars Daleckis’s Latvian Aurora Time-Lapse
• Kwon O Chul’s Yellowknife Aurora Gallery
• Ten Northern-Lights Regions: Geography, Darkness and Realistic Expectations

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