(CN) — The National Weather Service and National Oceanic and Atmospheric Administration have issued a G4-level severe geomagnetic storm watch for the weekend, starting midday Friday and extending through Sunday. It's the first time since 2005 that the weather agencies have forecast solar activity of this magnitude affecting the Earth.
"We have a high confidence that a series of coronal mass ejections, which are blasts of energetic particles and magnetic fields that depart the sun, are directed right towards Earth," Shawn Dahl, service coordinator for NOAA’s Space Weather Prediction Center, said in a Friday morning press call.
Dahl predicted the effects of geomagnetic storm would begin Friday evening, with less confidence as to what would unfold Saturday and Sunday. The solar activity would first have to arrive at the closest U.S. solar weather monitoring stations, NASA's Advanced Composition Explorer (ACE) satellite and NOAA's Deep Space Climate Observatory (DSCOVR) satellite. Both orbit the sun near the L1 Lagrange Point of the Sun-Earth system where the sun and Earth's gravity are in relative equilibrium.
"That's how we identify the arrival of these [coronal mass ejections] one million miles from Earth," Dahl explained.
NOAA scientists had observed at least five coronal mass ejections by Friday morning. By 1 p.m. central time, the agency had declared a "G4" geomagnetic event to be in progress.
As its name implies, a geomagnetic storm distorts the Earth's natural magnetic field and could have an adverse impact on electrical infrastructure on the ground and in space.
Potential effects could include power outages as well as disruptions to communications, radio navigation and satellite tracking. The NOAA has alerted satellite, power grid and communications operators to be on the lookout for those effects, Dahl said.
The coronal mass ejections that scientists have monitored thus far have moved at an average speed of about 800 kilometers, or 497 miles, per second. If that speed holds steady into the weekend, it would give observers on the ground about 20 to 45 minutes of heads up before the solar material reaches Earth.
Several unusually energetic sunspot regions of the sun's surface are the origin of this material. NOAA scientists have had their eye on these regions for several days, Dahl said, having observed solar flares from these areas since before Wednesday. One of the largest and most complex of these sunspot regions, located in the sun's southern hemisphere, is over 16 times the diameter of Earth.
"The activity is not over. The region is rotating as the sun rotates," Dahl said — adding that "it did produce another coronal mass ejection overnight."
Three severe geomagnetic storms have been observed during this solar activity cycle, which began in 2019.
This is the first one directed at Earth.
The last severe storm was detected this past March, foreshadowing the increased activity scientists are now observing. A level of severity above G4 also exists; the last G5 event to effect Earth occurred in October 2003. That storm caused electrical problems in countries nearer the poles, including power outages in Sweden and damage to power transformers in South Africa.
The worst case for this weekend, Dahl explained to reporters on Friday, would be a G5 storm on the scale of the so-called "Carrington Event" of 1859. The most intense geomagnetic storm in recorded history, it caused auroras that might have been visible as far south as the equator. That storm also reportedly shorted out telegraph stations around the world.
"That's an extreme-level event," Dahl reassured those in the press call. "We are not anticipating that, but we can't of course not [sic] discount that we could reach a low-end G5" event.
As with the Carrington Event, this weekend's increased solar activity does have an upside. It could provide people far south of the Arctic Circle a chance to view the northern lights.
The extent to which auroras will be visible over the weekend is still not known, and opinions vary by institution. The NOAA predicted auroras may be visible in a wide arc on Saturday night, extending as far south as Alabama and curving northwest to northern California.
The Geophysical Institute at the University of Alaska in Fairbanks gave an even more generous estimate, predicting people as far south as Austin, Texas may be able to see the northern lights on the low horizon. Meanwhile, those in Oklahoma City and Little Rock, Arkansas, may be able to see them directly overhead, the institute said — weather permitting.
"There's a chance here in the Midwest you might see it overhead," echoed Kevin Doom, a meteorologist with the National Weather Service in Chicago. "If not, it may be visible on the horizon."
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