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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Sep 27 1231 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

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

Protoni solari

Quiet

	10cm flux	Ap
27 Sep 2025	168	011
28 Sep 2025	169	017
29 Sep 2025	171	005

Solar Active Regions and flaring

Solar flaring activity was moderate over the past 24 hours, with four M-class flares and a few C-class flares. The strongest flare was a M1.6 flare (SIDC Flare 5585) peaking at 20:01 UTC on September 26 from beyond the east limb. There are currently eleven numbered active regions on the solar disk. SIDC Sunspot Groups 592, 614, 644, 648, 650 (NOAA Active Regions 4226, 4227, 4224, 4230, 4229) and SIDC Sunspot Group 652 are the most complex, all with magnetic type beta. SIDC Sunspot Group 640 (NOAA Active Region 4217) has rotated over the west limb. SIDC Sunspot Group 652 and SIDC Sunspot Group 653 (NOAA Active Regions 4232, magnetic type alpha) have rotated on disc from the east limb. SIDC Sunspot Group 654 has 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.

Espulsioni di massa coronale

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

Vento solare

The solar wind conditions (ACE) reflected mostly slow solar wind conditions. The solar wind speed decreased from approximately 460 km/s to approximately 360 km/s. The interplanetary magnetic field values were between 3 nT and 5 nT. The Bz component varied between -4 nT and 4 nT. The interplanetary magnetic field angle was mostly in the negative sector. Enhanced solar wind conditions are possible over the next 24 hours due to the high-speed stream associated with the small, equatorial, negative polarity coronal hole (SIDC Coronal Hole 133) that crossed the central meridian on September 25.

Geomagnetism

Geomagnetic conditions globally were mostly at quiet levels (NOAA Kp 1 to 2). Geomagnetic conditions locally were mostly at quiet to unsettled levels (K BEL 1 to 3). Unsettled to active conditions are possible over the next 24 hours due to the high-speed stream associated with the small, equatorial, negative polarity coronal hole (SIDC Coronal Hole 133) that crossed the central meridian on September 25.

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 19 was below the 1000 pfu threshold in the last 24 hours. The greater than 2 MeV electron flux measured by GOES 18 exceeded the 1000 pfu threshold between 17:00 UTC on September 26 and 01:00 UTC on September 27 and remained below the threshold for the rest of the last 24 hours. The greater than 2 MeV electron flux is expected to be 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): 140, based on 11 stations.

Solar indices for 26 Sep 2025

Wolf number Catania	///
10cm solar flux	165
AK Chambon La Forêt	011
AK Wingst	008
Estimated Ap	007
Estimated international sunspot number	148 - Based on 17 stations

Noticeable events summary

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

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