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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Sep 15 1231 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Minor storm expected (A>=30 or K=5)

Protoni solari

Quiet

	10cm flux	Ap
15 Sep 2025	124	035
16 Sep 2025	124	027
17 Sep 2025	124	015

Solar Active Regions and flaring

Solar flaring activity was at low levels over the past 24 hours. A total of 7 numbered sunspot groups were identified on the visible solar disk. The strongest activity was a C3.7 flare produced by SIDC Sunspot Group 640 (NOAA Active Region 4217) with peak time 15:14 UTC on Sept 15. This region, classified as magnetic type beta, has fully rotated onto the visible disk and was responsible for most of the flaring activity throughout the past 24 hours. SIDC Sunspot Group 621 (NOAA Active Region 4216), classified as magnetic type beta, has exhibited some growth and flux emergence. It has produced isolated C-class flaring. SIDC Sunspot Group 639 has also exhibited some growth, but has remained quiet. The solar flaring activity is expected to be at low levels over the next 24 hours with very likely C-class flares and chances of M-class flaring.

Espulsioni di massa coronale

Multiple coronal mass ejections (CMEs) have been observed to lift-off the east limb, but none of them carries an Earth- directed component. No other Earth-directed CMEs have been identified in the available coronagraph imagery over the past 24 hours.

Vento solare

Over the past 24 hours the solar wind parameters (as measured by ACE at L1) have registered the expected arrival of a high speed stream (HSS) possibly preceded by and mixed with an ICME arrival related to the CME from Sept 11. The HSS is associated with the recurrent SIDC Coronal Hole 116 (negative polarity), which re-started crossing the central meridian on Sept 10. The solar wind speed has reached a maximum value of 823 km/s around 06:00 UTC on Sept 15. The magnitude of the interplanetary magnetic field, B, reached 21 nT with a minimum Bz component of - 16.7 nT. The current solar wind speed is close to 640 km/s and the total B field has decreased to 14 nT. The B field phi angle has switched to the negative sector (directed towards the Sun). The solar wind conditions are expected to continue to be elevated under the HSS influence over the next days.

Geomagnetism

The geomagnetic conditions over the past 24 hours have globally reached major storm levels (with NOAA Kp = 6.67 between 00:00 and 03:00 UTC on Sept 15) preceded and followed by several periods of minor geomagnetic storms. Up to minor storm levels were registered locally over Belgium for the entire period. The geomagnetic conditions over the next days are expected to be at unsettled to minor storm levels with possible isolated moderate storm levels due to the ongoing influence of a high speed stream.

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 10 MeV electron flux (as measured by GOES 18 and GOES 19) has exceeded the 1000 pfu threshold over the last 24 hours and is expected to exceed the threshold again over the next 24 hours. The 24-hour electron fluence was at nominal levels and is expected to increase towards moderate levels in the next 24 hours.

Today's estimated international sunspot number (ISN): 081, based on 18 stations.

Solar indices for 14 Sep 2025

Wolf number Catania	///
10cm solar flux	122
AK Chambon La Forêt	043
AK Wingst	014
Estimated Ap	015
Estimated international sunspot number	069 - Based on 22 stations

Noticeable events summary

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

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