NOAA: Major solar storms strike Earth; G2 activity could disrupt power and communications in northern U.S.

Federal forecasters said a major geomagnetic storm struck Earth late Sunday and a follow-up disturbance is expected Monday, raising the possibility of localized power, satellite and radio interference across parts of the northern United States.

The National Oceanic and Atmospheric Administration's Space Weather Prediction Center reported a G3 (strong) geomagnetic storm hit late Sunday night and a G2 (moderate) event was forecast for Monday. NOAA said the highest likelihood of noticeable space-weather effects would persist through about 2 p.m. Eastern on Monday, with the greatest risk concentrated at high latitudes.

Geomagnetic storms occur when the Sun ejects streams of charged particles—often in the form of coronal mass ejections (CMEs)—that reach Earth and disturb its magnetic field. NOAA uses a five-step G-scale to rate such storms, from G1 (minor) to G5 (extreme). A G2 storm can lead to minor power-grid fluctuations, localized voltage irregularities, brief or degraded satellite operations and brief high-frequency radio blackouts.

NOAA listed at least 11 U.S. states as likely to be affected by Monday's activity: Alaska, Washington, Idaho, Montana, North Dakota, Minnesota, Michigan, Maine, Vermont, New Hampshire and Wyoming. Forecasters added that New York, Oregon, South Dakota and Wisconsin could also see effects if the event is stronger than currently projected. The agency said the G3 and G2 activity are part of the same solar event that left the Sun on Sept. 11.

Auroras were reported across northern portions of the United States during Sunday night's G3 storm. Stronger geomagnetic storms increase the chance of visible aurora or "Northern Lights" at lower-than-usual latitudes; NOAA recommended that observers go to dark areas away from city lights and consult real-time space-weather tools for the best viewing windows.

The forecast calls for the geomagnetic storm to weaken after midday Monday. NOAA projected only minor (G1) or no storm activity on Tuesday and Wednesday, though it cautioned that unsettled conditions could leave a roughly 30 percent chance of continued radio blackouts into the middle of the week in high-latitude regions. Smaller R1–R2 events, which can cause spotty GPS degradation and limited radio interference, were also expected over the weekend.

Power operators and satellite controllers routinely monitor space-weather forecasts and can take preventive measures such as adjusting grid settings, managing load and modifying satellite operations to reduce the risk of damage or outages during stronger storms. NOAA and other agencies advise owners of sensitive electronics and residents in high-latitude areas to have basic preparedness items—such as flashlights and backup power—available in the event of localized outages.

For most people, particularly those in southern regions of the United States, NOAA said the storms are unlikely to produce noticeable effects beyond an increased chance of auroral displays in northern skies. The Space Weather Prediction Center and other monitoring organizations continue to track solar activity and will update forecasts if the situation changes.