Severe Solar Storm Could Disrupt GPS, Light Up Skies

The northern lights could be visible as far south as Alabama and northern California on Monday night. The National Weather Service's Space Weather Prediction Center says one of the most severe solar radiation storms so far this century is hitting Earth, with a companion geomagnetic storm close behind, CNN reports. The event is expected to light up the sky with auroras far beyond their usual range and may interfere with satellites, GPS, and some radio communications.

• "An S4 severe solar radiation storm is now in progress—this is the largest solar radiation storm in over 20 years," the SWPC said in a post on X. "The last time S4 levels were observed was in October, 2003. Potential effects are mainly limited to space launch, aviation, and satellite operations."
• NOAA's Space Weather Scales go from G1 to G5 for geomagnetic storms and S1 to S5 for solar radiation storms.

• The intense Halloween space weather in 2003 contributed to power outages in Sweden and transformer damage in South Africa. This week's storm is not expected to be that disruptive, but NASA, airlines, the FAA, FEMA, and North American power grid operators have all been notified. Astronauts on the International Space Station are expected to move to better-shielded areas, a standard precaution during such events.
• The current disturbance is tied to an X-class solar flare—one of the most energetic categories—triggering a coronal mass ejection, a huge burst of plasma and magnetic fields from the sun. Fast-moving charged particles create the radiation storm; the slower coronal material slamming into Earth's magnetic field drives the geomagnetic storm that can jostle power systems and navigation signals.
• A large sunspot known as AR 4341 exploded into the solar flare around midday on Sunday, per the Weather Network. Coronal mass ejections typically take three to four days to reach Earth, but this one is unusually fast-moving.
• The SWPC said the G4 storm conditions were reached Monday afternoon. Shawn Dahl at the center said the coronal mass ejection will gradually weaken to G1 by Wednesday, the New York Times reports. "This is very rare," Dahl said. "We don't get a G4-level activity very often during the solar cycle."

• For skywatchers, the payoff could be significant. Forecasts suggest the northern lights may be visible across much of the northern US, possibly reaching as far south as Alabama and northern California. Cloudy conditions are expected around the Great Lakes, but "at least half of the lower 48 should be able to see it," David Roth, a meteorologist with the Weather Prediction Center, tells the Times. "The clearest places are Nevada, Utah, most of Colorado, Kansas, southern Missouri, Tennessee, Kentucky, southwest Virginia, Alabama and Florida." Even if the display looks faint, phone cameras may capture colors and detail that eyes miss, CNN notes.