Solar radiation storm in progress following long-duration X1.9 flare and Earth-directed CME
Following an X1.9 flare and associated full halo coronal mass ejection (CME) late on January 18, 2026, the ≥10 MeV proton flux rose above 100 pfu early on January 19. The event reached S2 – Moderate solar radiation storm levels, prompting extended warnings for continued elevated radiation conditions through the rest of the day.
Full halo coronal mass ejection (CME) produced by long-duration X1.9 solar flare on January 18, 2026. Credit: NASA SDO, NASA/ESA LASCO, Helioviewer, The Watchers
A solar radiation storm is currently in progress after a long-duration X1.9 solar flare from Active Region 4341 (S11E24), which peaked at 18:09 UTC on January 18. The eruption produced Type II and Type IV radio emissions and a 3 200 sfu F10.7 radio burst with a Castelli-U signature.
A full halo coronal mass ejection (CME) was first detected in GOES CCOR-1 imagery at approximately 18:30 UTC.
The ≥10 MeV proton flux initially surpassed 10 pfu at 22:55 UTC on January 18 (S1 – Minor) and then exceeded 100 pfu at 04:40 UTC on January 19, reaching S2 – Moderate levels.
At S2 – Moderate radiation storm intensity, radiation exposure for high-latitude and high-altitude flights may increase slightly, and satellite systems may experience occasional single-event upsets or surface charging. Minor high-frequency radio fades are possible at polar latitudes.
The Space Weather Prediction Center (SWPC) upgraded its warning for proton flux persistence through 23:59 UTC on January 19. Real-time GOES proton plots confirm a sustained rise in particle flux above the S1 threshold.
Moderate flare potential remains from Region 4341 through January 21, and the associated CME could intensify geomagnetic conditions on January 19–20, depending on its magnetic orientation. Geomagnetic activity is currently quiet to active under positive-polarity coronal-hole influence, but higher storm levels are possible once the CME reaches Earth.
An additional high-electron-flux alert, active since January 12, indicates continued charging risk for satellites. Yesterday’s maximum ≥2 MeV electron flux reached 4 619 pfu under the same coronal-hole regime.
Updates
11:55 UTC, January 19
The solar radiation storm intensified further on January 19, reaching S3 – Strong levels after ≥10 MeV proton flux exceeded 1 000 pfu at 10:20 UTC. This marks a significant escalation from earlier S1–S2 conditions following the X1.9 flare on January 18.
Solar radiation storms reaching S3 – Strong levels are relatively uncommon, typically occurring only a few times during an 11-year solar cycle.
At this intensity, increased radiation exposure is possible for high-latitude, high-altitude flights, while satellites may experience single-event upsets, imaging noise, minor efficiency losses in solar panels, and degraded or episodically blacked-out polar HF radio propagation.
15:40 UTC, January 19
Forecasts indicate that the full-halo coronal mass ejection produced by the January 18 X1.9 flare is expected to arrive at Earth early on January 20, with geomagnetic conditions likely to intensify rapidly afterward.
A G4 – Severe or greater geomagnetic storm is now predicted, with potential impacts including power grid disturbances at high latitudes, degraded or unavailable satellite navigation, spacecraft charging and increased drag, widespread HF radio disruptions, and auroral activity expanding well into mid-latitudes, potentially as far south as Alabama and northern California.
19:34 UTC, January 19
The solar radiation storm increased to the very rare S4 – Severe level at 18:10 UTC on January 19 after ≥10 MeV proton flux exceeded 10 000 pfu, significantly increasing radiation exposure risk for polar aviation, satellite systems, and causing widespread blackout of polar HF radio communications.
An interplanetary shock associated with the CME was detected at the Sun–Earth L1 point at 19:03 UTC, marking the onset of geomagnetic response. G4 – Severe or greater geomagnetic storming is expected.
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