Viewing archive of Sunday, 21 December 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Dec 21 1231 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
21 Dec 2025	122	022
22 Dec 2025	124	022
23 Dec 2025	126	011

Solar Active Regions and flaring

Solar flaring activity during the last 24 hours has been low, with few C-class flares. The strongest flare was a C3.1 flare (SIDC Flare 6459) peaking at 20:05 UTC on December 20, associated with SIDC Sunspot Group 735 (NOAA Active Region 4317, magnetic type beta). There are currently six numbered active regions on the solar disk. The most complex ones have a beta magnetic type. SIDC Sunspot Group 730 (NOAA Active Region 4313) and SIDC Sunspot Group 733 have decayed into plage. SIDC Sunspot Groups 735 (NOAA Active Region 4317) has rotated on disk from the east limb, 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 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

The southern, positive polarity coronal hole (returning SIDC Coronal Hole 128) has been crossing the central meridian since December 20.

Solar wind

The solar wind conditions (ACE) during the last 24 hours initially showed a return to the slow wind regime. The solar wind speed decreased to around 380 km/s. The interplanetary magnetic field values were between 3 nT and 6 nT. The Bz component varied between -3 nT and 4 nT. Enhanced solar wind conditions were observed starting from around 00:30 UTC on December 21, likely due to the early arrival of the high-speed stream from the southern, positive polarity coronal hole (SIDC Coronal Hole 128). The solar wind speed values increased from 400 km/s to around 650 km/s. The interplanetary magnetic field values increased to a maximum of 15 nT. The Bz component reached a minimum of -12 nT. The interplanetary magnetic field angle phi was mostly positive. Enhanced solar wind conditions are expected over the next 24 hours, under the ongoing influence of the high-speed stream from the southern, positive polarity coronal hole (SIDC Coronal Hole 128).

Geomagnetism

Geomagnetic conditions globally reached active levels (NOAA Kp 4- ) between 00:00 UTC and 03:00 UTC and between 09:00 UTC and 12:00 UTC on December 21. Geomagnetic conditions locally were mostly at unsettled levels (K Bel 3) during the last 24 hours. Mostly unsettled to active conditions (NOAA Kp 3 to 4), with possible minor storm conditions (NOAA Kp 5), 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 between 13:40 UTC on December 20 and 02:40 UTC on December 21. The greater than 2 MeV electron flux measured by GOES 19 was mostly above the 1000 pfu threshold until 05:00 UTC on December 21. The greater than 2 MeV electron flux is expected to be below the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence was at moderate levels but it is expected to return to normal levels over the next 24 hours.

Today's estimated international sunspot number (ISN): 064, based on 06 stations.

Solar indices for 20 Dec 2025

Wolf number Catania	///
10cm solar flux	120
AK Chambon La Forêt	015
AK Wingst	007
Estimated Ap	006
Estimated international sunspot number	055 - Based on 06 stations

Noticeable events summary

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

All times in UTC

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