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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Jul 27 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
27 Jul 2025	142	008
28 Jul 2025	141	008
29 Jul 2025	140	011

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares. The strongest flare was a C3.3 flare (SIDC Flare 4949) peaking at 14:25 UTC on July 26, which was associated with SIDC Sunspot Group 576 (NOAA Active Region 4160, magnetic type alpha). There are currently eight numbered active regions on the solar disk. SIDC Sunspot Groups 564, 570, 572 (NOAA Active Regions 4149, 4153, 4155) are the most complex Groups with magnetic type beta. SIDC Sunspot Group 575 (NOAA Active Region 4159) has decayed into a plage region. SIDC Sunspot Group 571 (NOAA Active Region 4158) has rotated over the west limb. The solar flaring activity is expected to be low over the next 24 hours, with C-class flares very likely and a chance for M-class flares.

Espulsioni di massa coronale

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

Fori coronali

A mid-latitude, negative polarity coronal hole (SIDC Coronal Hole 121) continues to cross the central meridian since June 26. An associated high-speed stream may arrive at Earth starting from July 29.

Vento solare

Over the past 24 hours, the solar wind parameters (ACE) were initially enhanced, under the waning influence of the high-speed stream from the negative polarity coronal hole (SIDC Coronal Hole 116) and a possible, but less certain, ICME arrival associated with the Coronal Mass Ejection (SIDC CME 530) that lifted off around 08:00 UTC on July 23. Solar wind parameters are gradually returning to a slow solar wind regime. Solar wind speed values have decreased from around 570 km/s to around 430 km/s. The interplanetary magnetic field values were between 7 nT and 11 nT. The Bz component varied between -9 nT and 10 nT. The interplanetary magnetic field angle phi was in the negative sector until around 16:30 UTC on July 26, when it flipped to the positive sector. Mostly slow solar wind conditions are expected over the next 24 hours.

Geomagnetism

Geomagnetic conditions globally were mostly at quiet to unsettled levels (NOAA Kp 1 to 3) and reached active levels (NOAA Kp 4) between 15:00 UTC and 18:00 UTC on July 26, due to a possible, but less certain, ICME arrival associated with Coronal Mass Ejection (SIDC CME 530) observed around 08:00 UTC on July 23. Geomagnetic conditions locally were mostly at quiet to unsettled levels (K BEL 1 to 3) and reached active levels (K BEL 4) between 12:00 UTC and 14:00 UTC and between 17:00 UTC and 20:00 UTC on July 26. Mostly quiet conditions, with possible unsettled intervals (NOAA Kp 1 to 3, K BEL 1 to 3), are expected globally and locally over the next 24 hours.

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

Over the past 24 hours, the greater than 2 MeV electron flux measured by GOES 19 was above the 1000 pfu threshold until around 20:00 UTC on July 26, when it fell below the threshold. The greater than 2 MeV electron flux measured by GOES 18 exceeded the 1000 pfu threshold between 15:30 UTC on July 26 and 03:00 UTC on July 27 and remained below the threshold for the rest of the last 24 hours. The greater than 2 MeV electron flux is expected to remain around the 1000 pfu threshold levels in the next 24 hours. The 24-hour electron fluence is presently at moderate levels and is expected to remain so over the next 24 hours.

Today's estimated international sunspot number (ISN): 130, based on 12 stations.

Solar indices for 26 Jul 2025

Wolf number Catania	///
10cm solar flux	143
AK Chambon La Forêt	018
AK Wingst	017
Estimated Ap	015
Estimated international sunspot number	153 - Based on 17 stations

Noticeable events summary

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

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