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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Oct 04 1231 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

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

Protoni solari

Warning condition (activity levels expected to increase, but no numeric forecast given)

	10cm flux	Ap
04 Oct 2025	166	014
05 Oct 2025	164	015
06 Oct 2025	162	011

Solar Active Regions and flaring

Solar flaring activity over the last 24 hours has been moderate, with one M-class flare and a few C-class flares. The strongest flare was an M1.2 flare (SIDC Flare 5667), peaking at 14:36 UTC on October 03, associated with SIDC Sunspot Group 659 (NOAA Active Region 4238, magnetic type beta). There are currently nine numbered active regions on the solar disk. The most complex is SIDC Sunspot Group 648 (NOAA Active Region 4230, magnetic type beta-gamma). SIDC Sunspot Group 659 (NOAA Active Region 4238) has rotated behind the west limb. SIDC Sunspot Group 648 (NOAA Active Region 4230) is currently rotating across the west limb. SIDC Sunspot Group 641 (NOAA Active Region 4240) has decayed into plage. SIDC Sunspot Group 664 (magnetic type alpha) has emerged in the southeast quadrant. The solar flaring activity is expected to be moderate over the next 24 hours, with M-class flares very likely and X-class flares unlikely.

Espulsioni di massa coronale

A slow, partial halo Coronal Mass Ejection (SIDC CME 571) was detected in LASCO/C2 and LASCO/C3 coronagraph imagery, lifting off the east limb starting from around 18:30 UTC on October 03. A possible association is a filament eruption in the northeast quadrant, observed in AIA 304 data around 16:00 UTC on October 03. Current analysis suggests a speed slower than 200 km/s and a small chance for a glancing blow arrival starting from the UTC morning on October 08. Two wide CMEs (SIDC CMEs 572 and 573) were observed in LASCO/C2 coronagraph imagery, lifting off the west limb, at 17:30 UTC on October 03 and at 06:30 UTC on October 04 respectively. They are most likely associated with eruptive activity near the west limb and they are not expected to impact Earth. No other Earth- directed CMEs were observed in the available coronagraph imagery over the last 24 hours.

Fori coronali

The equatorial, positive polarity coronal hole (SIDC Coronal Hole 123) is crossing the central meridian since September 30.

Vento solare

The solar wind conditions (ACE) were enhanced during the last 24 hours, under the ongoing influence of a high-speed stream from the two equatorial, positive polarity coronal holes (SIDC Coronal Holes 128 and 123). The solar wind speed decreased from around 700 km/s to around 600 km/s. The interplanetary magnetic field was around 5 nT. The Bz component ranged between -4 nT and 3 nT. The interplanetary magnetic field angle phi was predominantly in the positive sector. Enhanced solar wind conditions are expected over the next 24 hours, under the ongoing influence of the high-speed stream from SIDC Coronal Holes 128 and 123.

Geomagnetism

Geomagnetic conditions globally during the last 24 hours were at unsettled to active levels (NOAA Kp 3 to 4+). Geomagnetic conditions locally were mostly at unsettled levels (K Bel 3) during the last 24 hours, with an interval of active levels between 18:00 UTC and 21:00 UTC on October 03. Mostly unsettled to active conditions (NOAA Kp 3 to 4) are expected over the next 24 hours, under the ongoing influence of the high- speed stream from SIDC Coronal Holes 128 and 123.

Proton flux levels

The greater than 10 MeV proton flux increased but remained below the 10 pfu threshold over the past 24 hours. It is expected to remain below the threshold level over the next 24 hours, pending no eruptive activity from SIDC Sunspot Groups 648 and 659 (NOAA Active Regions 4230 and 4238).

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux measured by GOES 18 was above 1000 pfu threshold during the last 24 hours. The greater than 2 MeV electron flux measured by GOES 19 was mostly above 1000 pfu threshold during the last 24 hours, with short intervals under it. The greater than 2 MeV electron flux is expected to remain above the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence is presently at moderate levels and is expected to increase over the next 24 hours.

Today's estimated international sunspot number (ISN): 158, based on 13 stations.

Solar indices for 03 Oct 2025

Wolf number Catania	///
10cm solar flux	170
AK Chambon La Forêt	035
AK Wingst	024
Estimated Ap	029
Estimated international sunspot number	174 - Based on 14 stations

Noticeable events summary

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

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