Viewing archive of Friday, 19 September 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Sep 19 1231 UTC

SIDC Forecast

Solar flares

M-class flares expected (probability >=50%)

Geomagnetism

Quiet (A<20 and K<4)

Solar protons

Quiet

	10cm flux	Ap
19 Sep 2025	150	003
20 Sep 2025	151	004
21 Sep 2025	150	005

Solar Active Regions and flaring

Solar flaring activity was at low levels over the past 24 hours with only C-class flares identified. A total of 7 numbered sunspot groups were identified on the visible solar disk with SIDC Sunspot Group 637 (NOAA Active Region 4220) growing to be the largest and most complex active region, being classified as magnetic type beta-gamma- delta. This region was responsible for most of the flaring activity over the past 24 hours, including a C3.6 flare (SIDC Flare 5515) with peak time at 15:41 UTC on Sept 18. The remaining regions are classified as magnetic type beta. Isolated low C-class flaring was produced by SIDC Sunspot Group 639 (NOAA Active Region 4219) and SIDC Sunspot Group 643 (NOAA Active Region 4223). The solar flaring activity over the next 24 hours is expected to be at low to moderate levels with very likely C-class flares and 60% chances for M-class flaring.

Coronal mass ejections

No Earth-directed coronal mass ejections (CMEs) have been identified in the available coronagraph imagery over the past 24 hours.

Coronal holes

A mid-latitude negative polarity coronal hole (SIDC Coronal Hole 126) has reached the central meridian on Sept 19. A high speed stream emanating from this coronal hole is expected to reach the Earth on Sept 22.

Solar wind

Over the past 24 hours the solar wind parameters (as measured by ACE) have returned to slow solar wind conditions. The solar wind speed has further decreased to 400 km/s. The magnitude of the interplanetary magnetic field, B, remained weak with a maximum of 4.5 nT and a minimum Bz component of - 2.7 nT. The B field phi angle remained predominantly in the negative sector (directed towards the Sun). The solar wind conditions are expected to be at background slow solar wind levels over the next days.

Geomagnetism

The geomagnetic conditions over the past 24 hours were globally quiet with quiet to unsettled levels registered locally over Belgium. The geomagnetic conditions over the next days are expected to be predominantly quiet.

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 24 hours, pending no explosive eruptive activity related to the evolution of SIDC Sunspot Group 637 (NOAA Active Region 4220).

Electron fluxes at geostationary orbit

The greater than 10 MeV GOES electron flux has been entirely above the 1000 pfu threshold over the last 24 hours and is expected to exceed the threshold for long periods of time over the next 24 hours. The 24-hour electron fluence was at moderate levels and is expected to remain at moderate levels over the next days.

Today's estimated international sunspot number (ISN): 145, based on 17 stations.

Solar indices for 18 Sep 2025

Wolf number Catania	154
10cm solar flux	150
AK Chambon La Forêt	009
AK Wingst	007
Estimated Ap	007
Estimated international sunspot number	137 - Based on 18 stations

Noticeable events summary

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

All times in UTC

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