For the 4th day in a row, a stream of high-speed solar wind is blowing at 600 km/s (1.3 million mph) around Earth. The gaseous material is flowing from a wide hole in the sun’s atmosphere. It is so wide that Earth could remain inside the stream for another 2 or 3 days. During the weekend the stream of solar wind sparked G1 and G2-class geomagnetic storms. High atop Earth’s atmosphere, hot ribbons of plasma began to flow through our planet’s magnetic field. Suddenly, STEVE appeared… farther south than usual! You don’t have to travel to the Arctic Circle to meet STEVE. He might be coming to you.
“STEVE, the strange auroral arc, put in quite the appearance on Sunday night, with a fine show over southern Alberta lasting about an hour,” says Dyer. “It started as a faint arc in the east, then intensified, cutting across the entire sky.”
STEVE (Strong Thermal Emission Velocity Enhancement) was discovered by sky watchers in Alberta only a few years ago, although the phenomenon was surely active long before. The narrow ribbon is related to auroras, but has a distinct shape, color, and habitat. Researchers are now beginning to understand STEVE as a manifestation of hot plasma currents in the upper atmosphere.
Elizabeth MacDonald recently published a paper on STEVE. In it, they link STEVE to a phenomenon called “subauroral ion drifts” (SAIDs). Satellites have tracked thousands of SAIDs: They tend to appear most often during spring and fall and seem to prefer latitudes near +60 degrees.
But this weekend, STEVE traveled farther south than usual. Greg Ash saw the ribbon over Ely, Minnesota, at latitude +47.9 N:
“As you can imagine, I was totally stoked,” says Ash. “This was my first STEVE sighting and it was unforgettable. It was visible with the naked eye and I could see the pulsations of green with the purple.”
Elsewhere, STEVE was sighted in Tofte, Minnesota (+47.6N)
Buxton, North Dakota (+47.6 N)
Arcadia, Michigan, (+44.5N)
and Fort Frances, Ontario (+48.6N).
These relatively low latitude apparitions are an encouraging sign for sky watchers who wish to see the strange ribbon for themselves. You don’t have to travel to the Arctic Circle to meet STEVE. He might be coming to you. But it is still unknown why we see them always appearing always more nowadays.