Periodically, the sun spews out gigantic eruptions of particles into the solar system. Sometimes, when the solar eruptions are aimed right at Earth, the particles may create brilliant auroras in night skies in many parts of the planet. Then there are other occasions when the battering can damage satellites, mangle GPS signals and knock out power grids.
On Wednesday, a federal center issued a space weather severe storm watch after sun-watching spacecraft observed a large solar flare emanating from a sunspot in the sun’s northern hemisphere, accompanied by an explosion of particles known as a coronal mass ejection.
“The concerning thing here is that it was right in the center of the sun,” Shawn Dahl, the service coordinator for the Space Weather Prediction Center, which is part of the National Oceanic and Atmospheric Administration, said during a news conference Wednesday afternoon.
If the eruption was right in the center of the sun, that meant at least part of it was likely aimed right at Earth. It looked big enough to cause potential disruptions. The barrage could also result in Northern and Southern Lights being visible on Thursday evening, reaching much closer to the Equator than usual.
This was the second such watch, which is the space weather equivalent of a hurricane watch, to be issued by the center in the past 19 years.
The first, in May, put the United States on alert for a severe solar storm that appeared to be on its way to Earth. That solar storm reached the highest level of “extreme,” but the early warning allowed electrical utilities to prepare and helped prevent major outages.
The charged particles from the latest event — protons, electrons and helium nuclei — are speeding at more than 2.5 million miles per hour and are expected to start slamming into the Earth’s magnetic field on Thursday morning Eastern time.
Mr. Dahl said the storm would most likely not be as intense as the one in May. “The difference is, the one in May, we had a series of coronal mass ejections, one of them faster than the other,” Mr. Dahl said. “And it kind of swept everything together and just enhanced the effect.”
But the geomagnetic storm could last about 36 hours. If the storm reaches the severe level, the auroras in the Northern Hemisphere could stretch down into the middle of the United States, potentially as far south as Alabama.
The forecasts will remain largely guesswork until the waves of particles pass by two spacecraft, the NASA Advanced Composition Explorer, or ACE, and the Deep Space Climate Observatory, or DSCOVR.
Both are about one million miles from Earth, providing 15 to 30 minutes of warning before the solar storms arrive at Earth. At that point, the watch might be upgraded to a warning.
In May, the center started talking with power grid operators about six hours before the storm arrived.
This time, they reached out even earlier, because the power grid, already damaged by Hurricane Helene last month, will be further thrashed as Hurricane Milton bears down on Florida.
“With all the hurricane relief efforts going on and the inbound hurricane going into Florida and across the peninsula, we thought it prudent to immediately contact them now,” Mr. Dahl said. “We don’t know the true status there, but that’s just our concern.”
Neither the May eruption nor this week’s is as severe as one known as the Carrington Event that hit Earth in 1859, disrupting telegraph stations, or another in 1989 that caused a nine-hour blackout in Quebec.
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