Viewing archive of Tuesday, 23 September 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Sep 23 1231 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
23 Sep 2025	173	018
24 Sep 2025	174	008
25 Sep 2025	172	013

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares. The strongest flare was a C4.2 flare (SIDC Flare 5543) peaking at 16:09 UTC on September 22 from beyond the east limb. There are currently thirteen numbered active regions on the solar disk. The most complex one is SIDC Sunspot Group 640 (NOAA Active Region 4217) with magnetic type beta-gamma. SIDC Sunspot Group 621 (NOAA Active Region 4216, magnetic type alpha) and SIDC Sunspot Group 637 (NOAA Active Region 4220, magnetic type beta) are currently rotating over the west limb. SIDC Sunspot Group 647 has decayed into a plage region. SIDC Sunspot Group 648 (magnetic type beta) has rotated on disc from the east limb. SIDC Sunspot Groups 649 and 650 (both magnetic type beta) have emerged near the center of the disk. The solar flaring activity is expected to be moderate over the next 24 hours, with C-class flares expected and M-class flares likely.

Coronal mass ejections

A wide Coronal Mass Ejection (SIDC CME 561), was observed in LASCO/C2 and C3 coronagraph imagery starting from around 22:30 UTC on September 22, lifting off the north limb. No clear source was identified on the visible disk, suggesting a backsided event that will not impact Earth. A narrow Coronal Mass Ejection (SIDC CME 562) was observed in LASCO/C2 and C3 coronagraph imagery around 00:00 UTC on September 23, lifting off the southwest limb. It is associated with a prominence eruption observed in AIA 304 data around 22:00 UTC on September 22 at the southwest limb, and it is not expected to impact Earth. No other Earth-directed CMEs were observed in the available coronagraph imagery.

Solar wind

Over the past 24 hours, the solar wind parameters (ACE) continue to reflect the ongoing influence of the high-speed stream associated with the mid-latitude negative polarity coronal hole (SIDC Coronal Hole 126). Speed values continued to increase from approximately 430 km/s to the current value of approximately 580 km/s. The interplanetary magnetic field values varied between 6 nT and 18 nT. The Bz component varied between -13 nT and 17 nT. The interplanetary magnetic field angle was mostly in the negative sector. Enhanced solar wind conditions are expected over the next 24 hours under the waning influence of the high- speed stream associated with SIDC Coronal Hole 126.

Geomagnetism

Geomagnetic conditions globally were mostly at unsettled levels (NOAA Kp 3). Geomagnetic conditions locally were mostly at quite to unsettled levels (K BEL 2 to 3). Mostly quiet to unsettled conditions are expected globally and locally over the next 24 hours.

Proton flux levels

The greater than 10 MeV proton flux was below the 10 pfu threshold level over the past 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 over the 1000 pfu threshold until 18:30 UTC on September 22. The greater than 2 MeV electron flux measured by GOES 18 was mostly below the 1000 pfu threshold in the last 24 hours and exceed the 1000 pfu threshold between 17:00 UTC and 19:30 UTC on September 22. The greater than 2 MeV electron flux is expected to remain around the 1000 pfu threshold levels in 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): 197, based on 12 stations.

Solar indices for 22 Sep 2025

Wolf number Catania	///
10cm solar flux	172
AK Chambon La Forêt	025
AK Wingst	014
Estimated Ap	014
Estimated international sunspot number	165 - Based on 24 stations

Noticeable events summary

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

All times in UTC

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