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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Sep 22 1231 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
22 Sep 2025	177	029
23 Sep 2025	179	014
24 Sep 2025	179	008

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 C6.6 flare (SIDC Flare 5531) peaking at 21:16 UTC on September 21, which was associated with SIDC Sunspot Group 644 (NOAA Active Region 4224, magnetic type beta). There are currently eleven 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 647 (magnetic type alpha) has emerged in the southwest quadrant. The solar flaring activity is expected to be moderate over the next 24 hours, with C-class flares expected and M-class flares likely.

Espulsioni di massa coronale

A narrow Coronal Mass Ejection (SIDC CME 559) was observed in LASCO/C2 and C3 coronagraph imagery around 22:30 UTC on September 21, lifting off the northeast limb. It is associated with a prominence eruption observed in AIA 304 data around 20:30 UTC on September 21 at the northeast limb, and it is not expected to impact Earth. A Coronal Mass Ejection (SIDC CME 560), was observed in LASCO/C2 and C3 coronagraph imagery starting from around 23:00 UTC on September 21, lifting off the southwest limb. No clear source was identified on the visible disk, suggesting a backsided event that will not impact Earth. No other Earth- directed CMEs were observed in the available coronagraph imagery.

Vento solare

Over the past 24 hours, the solar wind parameters (ACE) were enhanced under the influence of the high-speed stream from the mid-latitude negative polarity coronal hole (SIDC Coronal Hole 126). Speed values increased from approximately 300 km/s to the current value of approximately 430 km/s. The interplanetary magnetic field values increased from 2 nT to 18 nT. The Bz component varied between -12 nT and 17 nT. The interplanetary magnetic field angle was mostly in the negative sector. Enhanced solar wind conditions due to the high-speed stream from the mid-latitude negative polarity coronal hole (SIDC Coronal Hole 126) are expected over the next 24 hours.

Geomagnetism

Geomagnetic conditions globally and locally were mostly at quiet to unsettled levels (NOAA Kp 1 to 3, K BEL 1 to 3). Active to minor storm conditions are expected over the next 24 hours due to the high-speed stream from the mid-latitude negative polarity coronal hole (SIDC Coronal Hole 126).

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 and GOES 19 was below the 1000 pfu threshold in the last 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): 166, based on 21 stations.

Solar indices for 21 Sep 2025

Wolf number Catania	///
10cm solar flux	176
AK Chambon La Forêt	011
AK Wingst	006
Estimated Ap	005
Estimated international sunspot number	172 - Based on 18 stations

Noticeable events summary

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

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