Viewing archive of Thursday, 25 September 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Sep 25 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
25 Sep 2025	182	006
26 Sep 2025	179	006
27 Sep 2025	178	014

Solar Active Regions and flaring

Solar flaring activity was moderate over the past 24 hours, with one M-class flare. The strongest flare was a M1.6 flare (SIDC Flare 5557) peaking at 19:13 UTC on September 24, which was associated with SIDC Sunspot Group 644 (NOAA Active Region 4224, magnetic type beta). There are currently eleven numbered active regions on the solar disk. SIDC Sunspot Groups 592, 640 (NOAA Active Regions 4226, 4217) are the most complex, all with magnetic type beta-gamma. SIDC Sunspot Group 637 (NOAA Active Region 4220) has rotated over the west limb. SIDC Sunspot Group 647 (magnetic type beta) has re-emerged in the southwest quadrant. SIDC Sunspot Group 651 (magnetic type beta) has emerged in the southwest quadrant. The solar flaring activity is expected to be moderate over the next 24 hours, with C-class flares expected and M-class flares likely.

Coronal mass ejections

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

Coronal holes

A small, equatorial, negative polarity coronal hole (SIDC Coronal Hole 133) is crossing the central meridian. An associated high- speed stream may arrive at Earth starting from September 28.

Solar wind

Over the past 24 hours, the solar wind parameters (ACE) continued to reflect the ongoing influence of the high-speed stream associated with the mid-latitude negative polarity coronal hole (SIDC Coronal Hole 126). Speed values ranged between 470 km/s and 550 km/s. The interplanetary magnetic field values were mostly around 5 nT. The Bz component varied between -4 nT and 5 nT. The interplanetary magnetic field angle was in the negative sector. Enhanced solar wind conditions, with a gradual return to the slow solar wind regime, can be expected over the next 24 hours, under the waning influence of the high-speed stream associated with SIDC Coronal Hole 126.

Geomagnetism

Geomagnetic conditions globally were mostly at quiet levels (NOAA Kp 1 to 2), with an interval of unsettled conditions (NOAA Kp 3- ) between 21:00 UTC on September 24 and 00:00 UTC on September 25. Geomagnetic conditions locally were mostly at quiet levels (K BEL 1 to 2), with an interval of unsettled conditions (K BEL 3) between 14:00 UTC and 17:00 UTC on September 24. Mostly quiet to unsettled conditions 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

The greater than 2 MeV electron flux measured by GOES 18 and GOES 19 was below the 1000 pfu threshold in the last 24 hours. The greater than 2 MeV electron flux is expected to be below the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence is presently at normal levels and is expected to remain so over the next 24 hours.

Today's estimated international sunspot number (ISN): 161, based on 12 stations.

Solar indices for 24 Sep 2025

Wolf number Catania	///
10cm solar flux	184
AK Chambon La Forêt	013
AK Wingst	008
Estimated Ap	008
Estimated international sunspot number	152 - Based on 16 stations

Noticeable events summary

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

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