On April 10th, 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."
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