A NEW CME JUST LEFT THE SUN (UPDATED): Yesterday, July 23rd, an unstable filament of magnetism in the sun's southern hemisphere exploded. The blast hurled a bright and interestingly textured CME into space: movie. NOAA analysts have modeled the CME and determined that it has no Earth-directed component. Solar flare alerts: SMS Text.

CME IMPACT SPARKS AURORAS AND STEVE: Arriving almost exactly on time, a CME hit Earth's magnetic field on July 23rd at 0259 UT. The impact sparked a G1-class geomagnetic storm with auroras from coast to coast in North America. "At about 12 midnight, I noticed a familiar light purple vertical glow to the east," reports Greg Ash of Ely, Minnesota. "It was STEVE!"

STEVE is actually not an aurora. The purple-colored arc is the glow from a supersonic river of gas, which flows through Earth’s magnetosphere during some geomagnetic storms. Short for "Strong Thermal Emission Velocity Enhancement," STEVE is a relatively recent discovery.

Lauri Kangas of Ontario, Canada, saw STEVE, too. "It was quite an active display with green pickets dancing in the Milky Way amongst the satellites and airplanes," says Kangas. "STEVE appeared and disappeared several times over an hour around midnight CDT."

Regular auroras (not STEVE) were sighted from New Hampshire to Washington, and one photographer recorded their glow as far south as Virginia:

Peter Forister took this picture from the Shenandoah National Park. Using a long exposure, he captured a layer-cake of color with red auroras in the middle and green airglow on top. "The auroras were visible for just a few minutes around 12:15 am EST," says Forister.

The storm has subsided now. There is a slight chance that it could flare up again because the solar wind velocity in the CME's wake remains above 500 km/s. If it does re-ignite, however, we would expect no more than minor G1-class activity. Aurora alerts: SMS Text.

PS. Congratulations to NOAA analysts for a pinpoint prediction. The CME, which was hurled into space by a solar tsunami eruption on July 21st, arrived within one hour of their forecast.