Viewing archive of Monday, 29 September 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Sep 29 1231 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
29 Sep 2025	175	017
30 Sep 2025	177	010
01 Oct 2025	179	010

Solar Active Regions and flaring

Solar flaring activity over the last 24 hours has been moderate, with two M-class flares and multiple C-class flares. The strongest flare was an M3.6 flare (SIDC Flare 5618) peaking at 01:45 UTC on September 29, associated with SIDC Sunspot Group 653 (NOAA Active Region 4232, magnetic type beta-gamma-delta). There are currently eleven numbered active regions on the solar disk. The most complex regions are SIDC Sunspot Groups 648, 653 and 657 (NOAA Active Regions 4230, 4232 and 4236), all with magnetic type beta-gamma-delta. SIDC Sunspot Group 658 (magnetic type beta) has emerged in the northeast quadrant. SIDC Sunspot Group 659 (magnetic type beta) has emerged in the southwest quadrant. The solar flaring activity is expected to be moderate to high over the next 24 hours, with M-class flares very likely and a small chance for X-class flares.

Coronal mass ejections

A Coronal Mass Ejection (SIDC CME 563) was observed in LASCO/C2 coronagraph imagery, starting from around 09:00 UTC on September 28. It is most likely associated with the M6.4 flare (SIDC Flare 5601) that peaked at 08:43 UTC on September 28. It is not expected to impact Earth. A large filament eruption was observed in AIA 304 data around 09:40 UTC on September 29, in the northwest quadrant. No associated CME was observed in the available coronagraph imagery, but further monitoring of the event is ongoing. No other Earth-directed Coronal Mass Ejections (CMEs) were observed in the available coronagraph imagery over the last 24 hours.

Coronal holes

An equatorial, positive polarity coronal hole (returning SIDC Coronal Hole 128) is crossing the central meridian. An associated high-speed stream is expected to arrive at Earth starting from the UCT morning of October 02.

Solar wind

The solar wind conditions (ACE) were slightly enhanced during the last 24 hours, likely due to an ICME arrival related to the slow, wide Coronal Mass Ejection that lifted off around 02:00 UTC on September 24 (SIDC CME 564). The solar wind speed ranged between 380 and 430 km/s. The interplanetary magnetic field increased from 11 to 15 nT. The Bz component reached a minimum of -13 nT. The interplanetary magnetic field angle phi was in the negative sector. A gradual decrease to slow solar wind conditions is expected over the next 24 hours.

Geomagnetism

Geomagnetic conditions globally were initially at unsettled levels (NOAA Kp 3- to 3), reaching minor storm levels (NOAA Kp 5-) since 12:00 UTC on September 29. The minor geomagnetic storm is likely due to an ICME arrival, related to the slow, wide Coronal Mass Ejection that lifted off around 02:00 UTC on September 24 (SIDC CME 564). Geomagnetic conditions locally were initially quiet to unsettled (K Bel 2-3), reaching active levels (K Bel 4) between 09:00 UTC and 11:00 UTC on September 29. Unsettled to active conditions (NOAA Kp 3-4), with possible isolated minor storm intervals (NOAA Kp 5) are expected over the next 24 hours.

Proton flux levels

The greater than 10 MeV proton flux was below the 10 pfu threshold 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 during the last 24 hours. It is expected to gradually increase 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): 189, based on 19 stations.

Solar indices for 28 Sep 2025

Wolf number Catania	///
10cm solar flux	171
AK Chambon La Forêt	015
AK Wingst	010
Estimated Ap	010
Estimated international sunspot number	165 - Based on 24 stations

Noticeable events summary

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

All times in UTC

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