The most powerful solar storm in nearly six years slammed Earth on March 24, surprising NOAA’s National Space Weather Service with a magnitude not expected.
U.S. National Oceanic and Atmospheric Administration, or NOAA, originally issued a magnetic storm watch on March 22 to come into effect March 23-25, with moderate G2 storm conditions expected. By March 24, the storm was upgraded to a severe G4 (on a 5-grade scale).
The storm’s unexpected ferocity made auroras visible as far south as Colorado and New Mexico in the U.S.
Geomagnetic storms are disturbances to Earth’s magnetic field caused by solar material from coronal mass ejections (CME) — large expulsions of plasma and magnetic field from the sun’s atmosphere. It turns out that this particular geomagnetic storm was triggered by a “stealth” CME which — as the name suggests — is rather tricky to detect.
NOAA(opens in new tab) ranks geomagnetic storms on a scale running from G1, which could cause an increase in auroral activity around the poles and minor fluctuations in power supplies, up to G5, which includes extreme cases like the Carrington Event — a colossal solar storm that occurred September 1859, which disrupted telegraph services all over the world and triggered auroras so bright and powerful that they were visible as far south as the Bahamas.
We can expect more extreme space weather events like this powerful geomagnetic storm as the sun builds towards a peak in its 11-year solar activity cycle, expected to occur in 2025.