Rare Videos of STEVE

April 11, 2018: Yesterday, a G1-class geomagnetic storm was brewing over Canada as a stream of solar wind buffeted Earth’s magnetic field. Matthew Wheeler of Robson Valley, British Columbia, stepped outside to see what was up–and STEVE appeared. “My dog barked at it for the entire hour it was visible,” says Wheeler. “It was flowing like a river at astonishing speed.” Click to play his must-see video:

STEVE may look like an aurora, but it is not. For one thing, it is soft purple, not green like typical auroras. And it has its own special form–tightly collimated into a narrow ribbon that can bisect the entire sky.

Researchers are only beginning to understand the phenomenon–aided by a chance encounter between STEVE and a European satellite a few years ago. In situ measurements revealed that STEVE is a hot (3000 degrees C) ribbon of ionized gas slicing through Earth’s upper atmosphere some 300 km above the ground. It appears unpredictably during some, but not all, geomagnetic storms.

Another video–“my best yet,” says Wheeler–shows the beautiful interaction between the soft-purple ribbon and nearby green “picket fence” auroras:

“The purple ribbon was moving much faster than the green pickets,” says Wheeler. “And while their forms varied from smooth to ragged and back again, their path across the sky was almost constant for the whole hour–as it has since I first noticed STEVE over this valley in the 1980s.”

Does STEVE really make dogs bark? “Mine does,” says Wheeler. “In addition to barking at STEVE, my giant Akbash astronomy dog, Patch, has barked at the space station since he was a pup, and proudly seen it off the farm every time. He is also a valuable spotter of meteor showers. When I hear him barking upwards, it is time to go outside.”

Realtime Aurora Photo Gallery

Strange Aurora-like Arc Sighted over Alaska: It’s “Steve”!

March 25, 2018: Last night, something happened at the edge of space over Alaska. More than 200 km above Anchorage, a hot ribbon of ionized gas sliced through Earth’s magnetosphere, creating a luminous arc that rivaled the Moon in brightness. Sanjana Greenhill witnessed the apparition:

“We noticed this perfect arc developing across the sky,” says Greenhill. “It didn’t seem like the aurora since it wasn’t moving much. The arc got brighter and then faded and then got brighter again. And then it dawned on me, this is STEVE!”

STEVE is an aurora-like phenomenon that researchers are only beginning to understand. For many years, northern sky watchers reported the form occasionally dancing alongside auroras. It was widely called a “proton arc” until researchers pointed out that protons had nothing to do with it. So members of the Alberta Aurora Chasers group gave it a new name: “Steve” (since upgraded to STEVE, an acronym for ‘Strong Thermal Emission Velocity Enhancement’).

The first clues to the nature of STEVE came in 2016 when one of the European Space Agency’s Swarm satellites encountered the phenomenon. “As the satellite flew straight though ‘Steve,’ the temperature jumped by 3000°C and the data revealed a 25 km-wide ribbon of gas flowing westwards at about 6 km/s (13,000 mph),” reports Eric Donovan from the University of Calgary.

Donovan and a team of colleagues led by Elizabeth MacDonald of NASA’s Goddard Space Flight Center have just published a paper on STEVE. In it, they confirm that STEVE is distinct from ordinary auroras, usually forming to the south of active Northern Lights. The mauve and purple colored arcs, they say, are related to supersonic rivers of gas called “subauroral ion drifts” (SAIDs), which flow through Earth’s magnetic field. Earth-orbiting satelites have tracked thousands of SAIDs: they tend to appear near latitude +60 degrees, and occur more frequently during spring and fall than summer and winter.

This last point means that now is the season for STEVE. The onset of northern spring seems to lure the arc out of winter hiding.

“I saw STEVE for the first time on March 18th,” reports Giuseppe Petricca , who took this sequence of pictures from the Isle of Lewis in Scotland:

“It was an ever-changing tornado, with violet tones, always in movement, always with different shapes,” he says. “Another wonder of Nature!”

The mystery of STEVE is far from solved. Researchers still don’t understand why STEVE is purple–or for that matter why the underlying rivers of gas should glow at all. “Further spectral analysis and modeling are needed,” say MacDonald et al.

In other words, keep an eye out for STEVE.

Realtime “Steve” Photo Gallery