A powerful X5.1 solar flare erupted from Active Region 4274 at 10:04 UTC on November 11. This was the fifth X-class solar flare detected since November 4 and the fourth from the same region, following X1.8 on November 4, X1.7 on November 9, and X1.2 on November 10.
This event had an associated Type-II (1 350 km/s) radio sweep and an F10.7 cm radio burst (10 000 sfu). There was also a Castelli-U radio burst, as well as an asymmetric halo CME, with an Earth-directed component.
The initial impact expected late on November 12 and peak geomagnetic effects on November 13. Two earlier CMEs, produced by the X1.7 flare on November 9 and the X1.2 flare on November 10, are also heading toward Earth, with their arrivals expected to precede and potentially merge with the latest CME, increasing the overall geomagnetic impact.
“This is making for a very complicated and difficult forecast, and SWPC forecasters are hard at it this Veteran’s Day, sorting together to create an updated forecast,” SWPC said.
The merging of the CMEs would be a perfect setup for significant geomagnetic storming and widespread aurora.
Following the X5.1 event, proton flux increased rapidly, reaching S2 – Moderate Solar Radiation Storm level by 12:10 UTC.
Potential impacts include small, increased radiation exposures for passengers and crew in high-latitude, high-altitude flights, infrequent single-event upsets to satellites, and minor effects on polar high-frequency (HF) radio propagation resulting in signal fades at lower frequencies.
SWPC issued a watch for geomagnetic storm category G4 – Severe or greater at 17:05 UTC today. The highest storm levels predicted by day are G4 – Severe on November 12, G3 – Strong on November 13, and G1 – Minor on November 14.
The watch supersedes all prior watches in effect.
Potential impacts include widespread voltage control issues and protective grid systems tripping key assets. Pipeline currents may intensify, while satellite systems could experience charging and orientation issues.
High-frequency radio communication and GPS navigation may be degraded or inoperative for several hours.
Aurora visibility could extend to latitudes as low as Alabama and northern California, depending on local conditions and the orientation of the interplanetary magnetic field.
Region 4274 continues to exhibit a beta-gamma-delta magnetic configuration with rotational and shearing features, maintaining the potential for additional X-class flares through at least November 13.
