The solar storm that seemed to be more fizzle than fury got much stronger early Friday before fading again. At its peak, it was the most potent solar storm since 2004, weather forecasters said.
No power outages or other technological disturbances were reported from the solar storm that started to peter out late Friday morning.
Solar storms, which can't hurt people, can disturb electric grids, GPS systems and satellites. They can also spread colorful Northern Lights farther south than usual, as the latest storm did Friday.
And more storms are coming. The federal government's Space Weather Prediction Center says the same area of the sun erupted again Thursday night, with a milder storm expected to reach Earth early Sunday.
The latest storm started with a flare on Tuesday, and had been forecast to be strong and direct, with one scientist predicting it would blast Earth directly like a punch in the nose. But it arrived Thursday morning at mild levels — at the bottom of the government's 1-5 scale of severity.
It strengthened to a level 3 for several hours early Friday as the storm neared its end. Scientists say that's because the magnetic part of the storm flipped direction.
"We were watching the boxer, expecting the punch. It didn't come," said physicist Terry Onsager at the National Oceanic and Atmospheric Administration's space weather center in Boulder, Colo. "It hit us with the back of the hand as it was retreating."
Skywatchers reported to NOAA shimmering colorful auroras in Michigan, Wisconsin and Seattle — areas that don't normally see the northern lights — said NOAA lead forecaster Bob Rutledge.
The storms are part of the sun's normal 11-year cycle, which is supposed to reach a peak next year.