Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Dec 20 1231 UTC

SIDC Forecast

Solar flares

C-class flares expected, (probability >=50%)

Geomagnetism

Quiet (A<20 and K<4)

Solar protons

Quiet

	10cm flux	Ap
20 Dec 2025	120	008
21 Dec 2025	121	007
22 Dec 2025	122	011

Solar Active Regions and flaring

Solar flaring activity during the last 24 hours has been moderate, with two M-class flares and a few C-class flares. The two strongest flares were two M1.0 flares. The first (SIDC Flare 6450), from beyond the west limb, peaked at 15:58 UTC on December 19. The second (SIDC Flare 6457), associated with SIDC Sunspot Group 703 (NOAA Active Region 4312, magnetic type alpha), peaked at 07:53 UTC on December 20. There are currently seven numbered active regions on the solar disk. The most complex ones have a beta magnetic type. SIDC Sunspot Groups 720 and 722 (NOAA Active Regions 4305 and 4307) have rotated behind the west limb. SIDC Sunspot Groups 723 and 728 (NOAA Active Regions 4308 and 4310) have decayed into plage. SIDC Sunspot Groups 731 and 733 (both magnetic type beta) have emerged in the southeast quadrant. SIDC Sunspot Groups 732 and 734 (both magnetic type beta) have emerged in the northeast quadrant. The solar flaring activity is expected to be low over the next 24 hours, with C-class flares very likely and a small chance for M-class flares.

Coronal mass ejections

No Earth-directed Coronal Mass Ejections (CMEs) were observed in the available coronagraph imagery during the last 24 hours.

Coronal holes

A southern, equatorial, positive polarity coronal hole (returning SIDC Coronal Hole 128) is crossing the central meridian. An associated high-speed stream is expected to arrive at Earth starting from the UTC evening on December 22.

Solar wind

The solar wind conditions (ACE) during the last 24 hours were enhanced, likely under the waning influence of high-speed streams from the north-south elongated, negative polarity coronal hole (SIDC Coronal Hole 136) and the southern, negative polarity coronal hole (SIDC Coronal Hole 137). The solar wind speed was initially around 550 km/s and has currently decreased to around 450 km/s. The interplanetary magnetic field values varied between 3 nT and 5 nT. The Bz component was between -3 nT and 4 nT. The interplanetary magnetic field angle phi was negative until 01:15 UTC on December 20, when it flipped to positive. A gradual return to the slow solar wind regime is expected over the next 24 hours.

Geomagnetism

Geomagnetic conditions globally were quiet (NOAA Kp 1 to 2) during the last 24 hours. Geomagnetic conditions locally reached unsettled levels (K Bel 3) between 19:00 UTC and 22:00 UTC on December 19 and between 09:00 UTC and 11:00 UTC on December 20. Mostly quiet conditions (NOAA Kp 1 to 2) are expected over the next 24 hours.

Proton flux levels

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

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux measured by GOES 18 was above the 1000 pfu threshold until 06:15 UTC on December 20. The greater than 2 MeV electron flux measured by GOES 19 was mostly above the 1000 pfu threshold during the last 24 hours. The greater than 2 MeV electron flux is expected to be above the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence was at moderate levels and is expected to remain so over the next 24 hours

Today's estimated international sunspot number (ISN): 044, based on 04 stations.

Solar indices for 19 Dec 2025

Wolf number Catania	///
10cm solar flux	118
AK Chambon La Forêt	012
AK Wingst	006
Estimated Ap	006
Estimated international sunspot number	049 - Based on 11 stations

Noticeable events summary

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