Long-duration M7.1 solar flare on December 31: NOAA reports R2 radio blackout, CME may brush Earth

On December 31, 2025, a long-duration M7.1-class solar flare erupted from active region AR 4324. NOAA/SWPC classified the event as an R2 (Moderate) radio blackout on the dayside of Earth. Preliminary data indicate a coronal mass ejection (CME) accompanied the flare; the probability of geomagnetic disturbances in early January is currently assessed at G1–G2.

Updated: January 1, 2026

Briefly:

Flare peak: 13:51 UTC (15:51 Kyiv) on 31 Dec 2025; duration: 13:12–14:11 UTC.
NOAA/SWPC: R2 (Moderate) radio blackout during the flare.
Evidence of CME (type II/IV radio emissions; preliminary shock speed ~893 km/s); trajectory and geoeffectiveness under analysis.
NOAA issued a G1–G2 watch for January 1–3, 2026; short-lived aurora bursts possible at higher latitudes.

What happened: M7.1 flare from AR 4324

According to The Watchers, the flare reached M7.1 at 13:51 UTC on December 31, 2025, lasting nearly an hour: start 13:12 UTC, end 14:11 UTC. The source was active region AR 4324 with a “beta–gamma” magnetic configuration, which raises the likelihood of additional strong flares.

The NOAA Space Weather Prediction Center (SWPC) reported an accompanying R2 (Moderate) Radio Blackout—a temporary degradation of HF communications on the sunlit side of Earth at peak time.

Why it matters: radio interference and communications impact

M-class flares emit powerful bursts of X-ray and ultraviolet radiation. The primary immediate effect is on the ionosphere: minutes after the flare, radio-wave propagation and navigation accuracy can degrade.

Systems most likely to experience R2 impacts

HF radio (including aviation and maritime bands) on the dayside: short dropouts and fades.
Navigation (GPS/GNSS): localized reductions in signal quality and positioning accuracy from ionospheric disturbance.
Satellite links and sensitive RF systems: transient increases in radio noise.

Was there a CME and when could geomagnetic storms occur?

The Watchers notes concurrent type II and IV radio emissions and a 10-cm radio burst—typical CME signatures. The report cites a type-II shock speed near ~893 km/s and suggests the source geometry could favor an Earth-directed component; final CME trajectory analysis was ongoing.

SpaceWeatherLive also indicates a CME on coronagraph imagery with a weak Earth-directed component and a possible glancing impact late on January 2; current expectations are up to G1, though the forecast may be refined as new data arrive.

Separately, NOAA/SWPC issued a G1–G2 watch for January 1–3, 2026, noting anticipated CME influence and elevated geomagnetic activity into early 2026.

What this means for Ukraine and Europe

At mid-latitudes the key risk is episodic activity rather than a guaranteed storm. If the CME proves more geoeffective, aurora chances rise first for higher latitudes (Scandinavia, northern Canada/USA). For Ukraine and Central Europe, noticeable aurora potential usually increases with G2–G3 levels and a sustained southward interplanetary magnetic field (negative Bz), so outcomes depend on solar-wind parameters at impact.

How to monitor the situation

NOAA/SWPC posts real-time alerts/watches/warnings and updates storm probabilities.
Solar-wind dashboards (speed, Bt/Bz) help assess whether the CME will couple strongly with Earth’s magnetosphere.
Pogodnik: watch for refined geomagnetic-storm updates in the final 12–24 hours before any CME arrival.

Sources

Glossary

M-class — flare magnitude category based on soft X-rays; M7.1 is a strong M-class flare.
AR (Active Region) — a magnetically complex sunspot region capable of flares.
R2 (Radio Blackout) — NOAA’s “Moderate” HF radio degradation on the dayside.
CME — coronal mass ejection; a plasma cloud that can trigger geomagnetic storms if it couples with Earth’s magnetosphere.
G1–G2 — NOAA geomagnetic storm levels (minor to moderate).
Bz — north–south component of the interplanetary magnetic field; sustained southward (negative) Bz favors stronger storms.

Q&A

Can an M7.1 flare by itself cause a geomagnetic storm?

No. Storms are driven by a CME (or enhanced solar-wind stream), not by the flare’s photons. The flare is a “marker” that a CME may have been launched.

Why does radio interference happen immediately but storms arrive later?

Radio/ionospheric effects are caused by flare radiation and occur within minutes. A CME typically takes 1–3 days to reach Earth, so geomagnetic impacts lag behind.

When will the forecast be most accurate?

Confidence improves once the CME is well resolved on coronagraphs and solar-wind parameters begin shifting upstream—typically within 24 hours of impact; see the Pogodnik app for geomagnetic-storm alerts.