Viewing archive of Tuesday, 16 December 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Dec 16 1231 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

Active conditions expected (A>=20 or K=4)

Solar protons

Quiet

	10cm flux	Ap
16 Dec 2025	118	008
17 Dec 2025	116	010
18 Dec 2025	114	016

Solar Active Regions and flaring

Solar flaring activity during the last 24 hours has been low, with only a few C-class flares. The strongest flare was a C3.9 flare (SIDC Flare 6435) from beyond the west limb, peaking at 17:28 UTC on December 15. There are currently seven numbered active regions on the solar disk. The most complex ones have a beta magnetic type. SIDC Sunspot Group 718 (NOAA Active Region 4304) has rotated behind the west limb. SIDC Sunspot Group 726 has decayed into plage. SIDC Sunspot Group 728 (NOAA Active Region 4310, magnetic type beta) has emerged in the northwest quadrant. SIDC Sunspot Group 729 (magnetic type alpha) has emerged in the northeast quadrant. The solar flaring activity is expected to be low over the next 24 hours, with C-class flares expected 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 over the last 24 hours.

Coronal holes

The southern, mid-latitude, negative polarity coronal hole (returning SIDC Coronal Hole 137) has been crossing the central meridian since December 15.

Solar wind

The solar wind conditions (ACE) during the last 24 hours were enhanced, likely under the ongoing influence of a high-speed stream from the northern, negative polarity coronal hole (SIDC Coronal Hole 142). The solar wind speed increased from 430 km/s to around 610 km/s. The interplanetary magnetic field increased from 4 to 14 nT. The Bz component was mostly positive with values up to 13 nT. The interplanetary magnetic field angle phi was mostly negative. Enhanced solar wind conditions are possible over the next 24 hours.

Geomagnetism

Geomagnetic conditions globally and locally were quiet to unsettled (NOAA Kp 1 to 3+, K Bel 1 to 3) during the last 24 hours. Quiet to unsettled conditions, with a small chance of isolated periods of active conditions (NOAA Kp 4), 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 and GOES 19 was close to the 1000 pfu threshold but remained below it during the last 24 hours. It is expected to remain mostly below the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence is presently at normal levels and is expected to remain so over the next 24 hours.

Today's estimated international sunspot number (ISN): 072, based on 06 stations.

Solar indices for 15 Dec 2025

Wolf number Catania	110
10cm solar flux	118
AK Chambon La Forêt	012
AK Wingst	006
Estimated Ap	004
Estimated international sunspot number	071 - Based on 15 stations

Noticeable events summary

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

All times in UTC

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