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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Dec 31 1236 UTC

SIDC Forecast

Brillamenti solari

M-class flares expected (probability >=50%)

Geomagnetism

Minor storm expected (A>=30 or K=5)

Protoni solari

Quiet

	10cm flux	Ap
31 Dec 2025	179	024
01 Jan 2026	176	028
02 Jan 2026	176	018

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares recorded. The largest flare was a C5.9 flare (SIDC Flare 6546) peaking on December 31 at 01:32 UTC, which was produced by SIDC Sunspot Group 745 (NOAA Active Region 4325). This region is the largest on disk and was responsible for most of the flaring activity (Beta-Delta magnetic configuration). There are currently 8 numbered regions on the disk. SIDC Sunspot Group 740 (NOAA Active Region 4321) has rotated over the west limb. SIDC Sunspot Groups 744 and 735 (NOAA Active Regions 4324 and 4317, respectively) are the other notable regions on disk but were mostly quiet. A new region emerged in the eastern hemisphere (SIDC Sunspot Group 750, N14E40) and SIDC Sunspot Group 712 (NOAA Active Regions 4330) decayed. The remaining regions are simple and mostly quiet. Solar flaring activity is expected to be moderate over the next 24 hours, with M-class flares expected and a chance for X-class flares.

Espulsioni di massa coronale

No new Earth-directed CMEs were observed in the available coronagraph imagery.

Vento solare

Over the past 24 hours, the solar wind parameters reflected a slow solar wind regime. The solar wind speed ranged between 370 and 460 km/s. The interplanetary magnetic field ranged between 2 and 10 nT, and Bz had a minimum of -6 nT. The interplanetary magnetic field phi angle was mostly in the positive sector (directed away from the Sun). Enhanced solar wind conditions are expected over the next 24 hours, due the combined effect of the high speed stream arrival associated with SIDC Coronal Hole 140 (negative polarity) and the glancing blow of a CME from December 28.

Geomagnetism

Geomagnetic conditions were at quiet to unsettled levels globally (NOAA Kp 1 to 3) and locally (K BEL 1 to 3) over the past 24 hours. Minor storm conditions are expected with possible moderate storm intervals possible, due to the expected high speed stream and CME arrival.

Proton flux levels

The greater than 10 MeV proton flux was below the 10 pfu threshold over the past 24 hours. It is expected to remain below this threshold level over the next 24 hours.

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux, as measured by GOES-18 and GOES-19 satellites, was above the 1000 pfu threshold for the first part of the period and decreased below it from 09:00 UTC December 31. The greater than 2 MeV electron flux is expected to again briefly exceed the 1000 pfu threshold over the next 24 hours but is expected to continue to gradually decrease from January 01, due to the anticipated high speed stream arrival. The electron fluence was at moderate levels and is expected to be at low to moderate levels for the next 24 hours.

Today's estimated international sunspot number (ISN): 137, based on 09 stations.

Solar indices for 30 Dec 2025

Wolf number Catania	115
10cm solar flux	182
AK Chambon La Forêt	014
AK Wingst	008
Estimated Ap	007
Estimated international sunspot number	139 - Based on 20 stations

Noticeable events summary

Provided by the Solar Influences Data analysis Center© - SIDC - Processed by SpaceWeatherLive

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