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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Jul 31 1244 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

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

Protoni solari

Quiet

	10cm flux	Ap
31 Jul 2025	150	011
01 Aug 2025	152	013
02 Aug 2025	151	011

Solar Active Regions and flaring

Solar flaring activity was at low levels with low C-class flaring over the past 24 hours. A total of 11 numbered sunspot groups were identified on the visible solar disk, all of them being magnetically simple, classified as magnetic type beta or alpha. The most notable activity was a C2.1 flare (SIDC Flare 4971) with peak time 19:43 UTC on on July 30, produced by SIDC Sunspot Group 555 (NOAA Active Regions 4141, 4161). Other notable low C-class flaring was produced from behind the west limb, as well as by SIDC Sunspot Group 572 (NOAA Active Region 4155), the newly rotated region near the east limb, SIDC Sunspot Group 581 (NOAA Active Region 4165) and a few other regions. Several short-lived regions have decayed and some are rotating behind the west limb. A rapid flux emergence resulted in the formation of SIDC Sunspot Group 587 (NOAA Active Region 4166), which has so far been inactive. The solar flaring activity is expected to be at low levels over the next 24 hours, with C-class flares very likely and some chances for M-class flaring.

Espulsioni di massa coronale

A large filament has erupted in the north-east quadrant starting around 03:30 UTC on July 31 causing related coronal dimming in the SDO/AIA imagery. No Earth-directed coronal mass ejection (CME) has been associated with this event. No other Earth-directed CMEs have been identified in the available coronagraph imagery over the past 24 hours.

Vento solare

Over the past hours the solar wind parameters as measured by ACE have registered a mild connection to a high-speed stream from a negative polarity coronal hole. The magnitude of the interplanetary magnetic field (B) reached 12.5 nT with a minimum north-south component, Bz, of -9.7 nT. The solar wind speed reached a maximum of about 600 km/s and is currently below 450 km/s. The B field phi angle remained predominantly in the negative sector (directed towards the Sun). Enhanced solar wind conditions are expected to continue over the next day and a smooth return towards nominal slow solar wind conditions is expected by the end of Aug 02.

Geomagnetism

The geomagnetic conditions over the past 24 hours were quiet to unsettled. Predominantly quiet to unsettled geomagnetic conditions are expected for the next 48 hours with possible isolated active periods.

Proton flux levels

Over the past 24 hours the greater than 10 MeV GOES proton flux has been at nominal levels and is expected to remain at nominal levels over the next days.

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux as measured by GOES 18 has reached the 1000 pfu threshold over the last 24 hours, while the greater than 2 MeV electron flux as measured by GOES 19 remained below the 1000 pfu threshold. The greater than 2 MeV electron flux is expected to exceed the 1000 pfu threshold again in the next 24 hours. The 24-hour electron fluence was at nominal levels and is expected to be at the border between nominal and moderate levels in the next 24 hours.

Today's estimated international sunspot number (ISN): 156, based on 21 stations.

Solar indices for 30 Jul 2025

Wolf number Catania	144
10cm solar flux	149
AK Chambon La Forêt	018
AK Wingst	014
Estimated Ap	011
Estimated international sunspot number	149 - Based on 33 stations

Noticeable events summary

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

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