Viewing archive of Tuesday, 30 September 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Sep 30 1231 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
30 Sep 2025	193	032
01 Oct 2025	195	017
02 Oct 2025	197	045

Solar Active Regions and flaring

Solar flaring activity over the last 24 hours has been moderate, with four M-class flares and a few C-class flares. The strongest flare was an M2.7 flare (SIDC Flare 5644), peaking at 09:40 UTC on September 30, associated with SIDC Sunspot Group 614 (NOAA Active Region 4227, magnetic type beta). There are currently eleven numbered active regions on the solar disk. The most complex region is SIDC Sunspot Groups 648 (NOAA Active Region 4230, magnetic type beta-gamma-delta). SIDC Sunspot Group 660 (magnetic type beta) has emerged in the northwest quadrant. Returning SIDC Sunspot Group 641 (magnetic type beta) has rotated on disk from the northeast limb. 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 565) was observed in LASCO/C2 and STEREO/COR2 coronagraph imagery, lifting off the southwest quadrant, starting from around 09:45 UTC on September 30. It is most likely associated with the M2.7 flare (SIDC Flare 5644) that peaked at 09:40 UTC on September 30. It is not expected to impact Earth. No other Earth- directed Coronal Mass Ejections (CMEs) were observed in the available coronagraph imagery over the last 24 hours.

Coronal holes

The equatorial, positive polarity coronal hole (returning SIDC Coronal Hole 128) is crossing the central meridian since September 29. An associated high-speed stream is expected to arrive at Earth starting from the UCT morning of October 02. A second, elongated, equatorial, positive polarity coronal hole (SIDC Coronal Hole 123) is crossing the central meridian. An associated high-speed stream is expected to arrive at Earth starting from the UTC evening of October 02.

Solar wind

The solar wind conditions (ACE) were 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 increased from 380 to around 470 km/s. The interplanetary magnetic field increased from 11 to 17 nT. The Bz component reached a minimum of -16 nT. The interplanetary magnetic field angle phi changed from negative to positive around 16:30 UTC on September 29. A gradual decrease to slow solar wind conditions is expected over the next 24 hours

Geomagnetism

Geomagnetic conditions globally were initially at minor storm levels (NOAA Kp 5- to 5), reaching major storm levels (NOAA Kp 7+) between 03:00 UTC and 06:00 UTC on September 30. Geomagnetic conditions locally reached moderate storm levels (K Bel 6) between 04:00 UTC and 07:00 UTC on September 30. Current geomagnetic conditions are at moderate storm levels globally (NOAA Kp 6) and active levels locally (K Bel 4). The geomagnetic storms occurred 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). Mostly active to minor storm conditions (NOAA Kp 4 to 5), with a small chance for isolated moderate storm intervals (NOAA Kp 6), 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): 191, based on 21 stations.

Solar indices for 29 Sep 2025

Wolf number Catania	212
10cm solar flux	186
AK Chambon La Forêt	057
AK Wingst	024
Estimated Ap	025
Estimated international sunspot number	189 - Based on 25 stations

Noticeable events summary

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

All times in UTC

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