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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Oct 25 1231 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

Quiet

	10cm flux	Ap
25 Oct 2025	133	017
26 Oct 2025	135	017
27 Oct 2025	137	043

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with several C-class flares recorded. The largest flare was a C1.6 flare (SIDC Flare 5872), peaking at 10:23 UTC on October 25, associated with SIDC Sunspot Group 653 (NOAA Active Region 4267; magnetic type alpha). There are currently seven numbered active regions on the visible solar disc. SIDC Sunspot Group 653 (NOAA Active Region 4267) was the main driver of the flaring activity observed over the past 24 hours, together with SIDC Sunspot Group 672 (NOAA Active Region 4256). SIDC Sunspot Group 607 (NOAA Active Region 4254; magnetic type alpha) is approaching the west limb. A new region emerged and was numbered SIDC Sunspot Group 683 (magnetic type beta) near S12E51, but remained quiet. The remaining active regions are relatively simple (magnetic type alpha or beta) and did not produce any significant flaring activity. Solar flaring activity is expected to be low over the next 24 hours, with C-class flares very likely and a small chance for M-class flares.

Espulsioni di massa coronale

The faint coronal mass ejection (SIDC CME 586) was observed in SOHO/LASCO-C2 imagery, starting at 14:36 UTC on October 23 and first reported yesterday. While the bulk of the ejecta is expected to miss Earth, a mild glancing blow could be possible on October 27. No other Earth-directed CMEs were detected in the available coronagraph imagery over the past 24 hours.

Fori coronali

A large recurrent positive polarity coronal hole (SIDC Coronal Hole 134) reached the central meridian at around 12:00 UTC today. An associated high-speed stream may affect the solar wind environment near Earth from late October 27.

Vento solare

Over the past 24 hours, solar wind parameters (ACE and DSCOVR) reflected the waning influence of a high-speed stream (HSS). The solar wind speed decreased from 580 to 430 km/s. The interplanetary magnetic field remained weak, below 6 nT, and its southward component fluctuated between -6 nT and 6 nT. A gradual transition to slow solar wind conditions is expected over the next few days, with a chance of a weak enhancement from October 27 due to the possible glancing blow from SIDC CME 586 and the arrival of a high-speed stream from a large positive polarity coronal hole (SIDC Coronal Hole 134).

Geomagnetism

Geomagnetic conditions reached active levels globally (NOAA Kp = 4) between 03:00 and 06:00 UTC on October 25 and locally over Belgium (K-Bel = 4) at around 18:00 UTC on October 24, due to mild HSS influence. Mostly unsettled geomagnetic conditions are expected over the next 24 hours. On October 27-28, geomagnetic conditions are expected to reach active and minor storm levels, with a chance of isolated moderate storm periods due to the expected HSS and a possible glancing blow from SIDC CME 586.

Proton flux levels

The greater than 10 MeV GOES proton flux was below the 10 pfu threshold level over the past 24 hours and is expected to remain so for 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. The greater than 2 MeV electron flux is expected to remain below the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence was at normal levels and is expected to be at normal levels over the next 24 hours.

Today's estimated international sunspot number (ISN): 099, based on 07 stations.

Solar indices for 24 Oct 2025

Wolf number Catania	105
10cm solar flux	134
AK Chambon La Forêt	020
AK Wingst	012
Estimated Ap	012
Estimated international sunspot number	098 - Based on 26 stations

Noticeable events summary

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

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