Viewing archive of Thursday, 16 October 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Oct 16 1233 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

Warning condition (activity levels expected to increase, but no numeric forecast given)

	10cm flux	Ap
16 Oct 2025	168	017
17 Oct 2025	172	014
18 Oct 2025	176	006

Solar Active Regions and flaring

Solar flaring activity was moderate over the past 24 hours with 4 M-class flares recorded. The largest flare was an M2.7 flare (SIDC Flare 5791) peaking on October 15 at 22:28 UTC, which was produced by SIDC Sunspot Group 639 (NOAA Active Region 4246). This is the most complex on disk and was responsible for all of the M-class flaring activity. SIDC Sunspot group 621 (NOAA Active region 4248) decreased in complexity slightly. A new region emerged and was numbered SIDC Sunspot Group 671 currently located at S08E49. Another new region just beyond the east limb was responsible for some C-class flaring activity. The remaining regions on disk were mostly quiet and either stable or in decay. The solar flaring activity is expected to be moderate over the next 24 hours, with M-class flares expected and a chance for X-class flares.

Coronal mass ejections

A Coronal Mass Ejections (CME) observed to the north-east from 15:19 UTC October 15 in SOHO/LASCO-C2 data, appears to be made up of two CMEs. One of which is likely associated with an M1.1 flare (SIDC Flare 5784) peaking on October 15 at 14:10 UTC produced by SIDC Sunspot Group 639 (NOAA Active Region 4246). The second CME to the north is likely a back sided event. Initial analysis suggests that these CMEs are not expected to impact Earth. No new Earth directed Coronal Mass Ejections (CMEs) were observed in the available coronagraph imagery.

Coronal holes

SIDC Coronal Hole 126 (extended equatorial coronal hole with a negative polarity) began to transit the central meridian on October 16.

Solar wind

The solar wind conditions reflected the gradual return to a slow solar wind regime. The solar wind speed gradually decreased from 500 km/s to around 400 km/s. The interplanetary magnetic field ranged between 0 and 8 nT. Bz ranged between -3 nT and 3 nT. Over the next 24 hours the solar wind conditions may become enhanced, due to a possible ICME arrival from the CME observed on October 12 and due to the glancing blow from the CMEs observed on October 13.

Geomagnetism

Geomagnetic conditions were at quiet levels globally (Kp 1-2. Locally, unsettled conditions were observed (K Bel 3). Unsettled to active conditions are expected on October 16, with periods of minor storm conditions (Kp 5) possible in response to the possible CME arrival.

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 this threshold level over the next 24 hours. There is a small chance of an increase related to any high-level flaring, particularly from SIDC Sunspot Group 639 (NOAA Active Region 4246).

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux measured by GOES 18 and GOES 19 exceeded the 1000 pfu threshold. The greater than 2 MeV electron flux is expected to again exceed the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence was at moderate levels and is expected to be at moderate levels over the next 24 hours.

Today's estimated international sunspot number (ISN): 126, based on 07 stations.

Solar indices for 15 Oct 2025

Wolf number Catania	///
10cm solar flux	162
AK Chambon La Forêt	012
AK Wingst	012
Estimated Ap	012
Estimated international sunspot number	120 - Based on 17 stations

Noticeable events summary

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

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