Long-duration M7.1 solar flare erupts from AR 4324, producing Earth-directed CME
A long-duration solar flare measuring M7.1 at its peak erupted from Active Region 4324 at 13:51 UTC on December 31, 2025. The event started at 13:12 and ended at 14:11 UTC.
M7.1 solar flare on December 31, 2025. Credit: NASA SDO/AIA 304, The Watchers
A Type IV and Type II (estimated velocity of 893 km/s) radio emissions were associated with the flare event, suggesting a strong coronal mass ejection (CME) was produced.
In addition, a 10cm Radio Burst lasting 22 minutes and with a peak flux of 550 sfu was registered from 13:31 to 13:53 UTC. A 10cm radio burst indicates that the electromagnetic burst associated with a solar flare at the 10cm wavelength was double or greater than the initial 10cm radio background. This can be indicative of significant radio noise in association with a solar flare. This noise is generally short-lived but can cause interference for sensitive receivers, including radar, GPS, and satellite communications.
Radio frequencies were forecast to be most degraded over the South Atlantic and parts of Africa and South America at the time of the flare.
Analysis of the event showed it produced a partial halo CME off the NE limb, with arrival to Earth expected late on January 2 to early January 3 (UTC).
Region 4324 has a ‘beta-gamma’ magnetic configuration and is capable of producing more strong eruptions on the Sun. Earth-directed CMEs from this region remain a possibility in the days ahead.
Solar activity was at low levels in 24 hours to 12:30 UTC today, with a few C-class flares mostly from regions 4324 and 4325, both of which had appreciable magnetic flux emergence and shear.
The greater than 2 MeV electron flux, measured by GOES-19, reached high levels with a peak of 5 612 pfu at 15:45 UTC on December 30, and decreased to moderate levels after 19:15 UTC. Moderate 2 MeV electron flux is expected through January 2 as we enter a coronal hole high-speed stream (CH HSS). There is a slight chance (10%) for S1 – Minor solar radiation storm during the same period.
Solar wind parameters remained at background levels during the first half of the reporting period. Conditions became slightly enhanced after December 30 at 22:35 UTC, when the total interplanetary magnetic field strength (Bt) increased from an average of about 5 nT to around 10 nT.
The north–south component of the magnetic field (Bz) was generally positive (northward), fluctuating between −5 and 10 nT. Solar wind speed increased gradually over the period from approximately 400 km/s to about 450 km/s. The interplanetary magnetic field phi angle remained mostly positive (away from the Sun).
Solar wind parameters are expected to continue strengthening through January 1 due to the influence of multiple coronal hole high-speed streams. A possible sector boundary crossing is forecast for January 2.
Conditions on January 1 are expected to be particularly disturbed, as a glancing interaction is possible from multiple coronal mass ejections that departed the Sun between December 28 and December 30.
Geomagnetic activity remained at quiet to unsettled levels over the past 24 hours.
Geomagnetic activity is expected to range from quiet to active on December 31. On January 1, conditions may increase to unsettled to G1 -Minor geomagnetic storm levels, before easing back to unsettled to active levels on January 2.
References:
1 Forecast Discussion – SWPC – Issued at 12:30 UTC on December 31, 2025
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