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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Aug 21 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
21 Aug 2025	119	011
22 Aug 2025	125	007
23 Aug 2025	127	007

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares identified. A total of 7 numbered sunspot groups were identified on the disk over the past 24 hours, having all Alpha or Beta magnetic configuration. The largest flare was a C3.2 flare (SIDC Flare 5181) peaking on August 21 at 00:11 UTC, which was produced by SIDC Sunspot Group 607 (NOAA Active Region 4191). Solar flaring activity is expected to be low over the next 24 hours, with C-class flares likely and a small chance for M-class flares.

Espulsioni di massa coronale

A first Coronal Mass Ejection (CME) was detected in SOHO/LASCO-C2 data from 05:12 UTC Aug 20 mainly directed to the south-east and a second CME was detected in SOHO/LASCO-C2 data from 10:36 UTC Aug 20 mainly directed to the northeast. Both CME originated from on/beyond the east limb and are not expected to impact Earth. A third, almost halo, CME was detected in SOHO/LASCO-C2 data from 08:24UTC Aug 21. Initial analysis indicates it is a back-sided event.

Vento solare

Fast solar wind conditions were recorded over the past 24 hours and is now gradually transiting to slow solar wind conditions. The solar wind speed has decreased from around 600 to 446 km/s over the past 24 hours. The interplanetary magnetic field is around 6 nT, with the Bz reaching a minimum value of -5 nT. In the next 24 hours, we expect the continuation of the gradual transition from fast to slow solar wind.

Geomagnetism

Geomagnetic conditions were globally and locally quiet to unsettled (Kp 3 and K Bel 3). Quiet to unsettled conditions are expected in the next 24 hours.

Proton flux levels

The greater than 10 MeV proton flux remained below the 10 pfu threshold and is expected to remain so over the next days.

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux as measured by GOES 18 remained below the 1000 pfu alert threshold (GOES 19 measurements indicated a short and minimal crossing of the threshold), and is expected to remain below the threshold during the next 24 hours. The 24h electron fluence was at normal levels and is expected to remain so.

Today's estimated international sunspot number (ISN): 068, based on 16 stations.

Solar indices for 20 Aug 2025

Wolf number Catania	059
10cm solar flux	120
AK Chambon La Forêt	017
AK Wingst	014
Estimated Ap	015
Estimated international sunspot number	057 - Based on 21 stations

Noticeable events summary

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

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