Viewing archive of Friday, 31 October 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 Oct 31 1231 UTC

SIDC Forecast

Solar flares

Quiet conditions (<50% probability of C-class flares)

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
31 Oct 2025	120	040
01 Nov 2025	122	040
02 Nov 2025	124	020

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares identified. A total of 5 numbered sunspot groups were identified on the disk over the past 24 hours. The largest flare was a C1.8 flare (SIDC Flare 5884) peaking on October 31 at 02:01 UTC, from a region behind the east limb. Solar flaring activity is expected to be low over the next 24 hours, with a C-class flares expected. The region rotating into view from the east limb may increase flaring activity.

Coronal mass ejections

There have been several relevant CMEs since our last report, after the backside halo from early 30 October (reported yesterday). The first one was related to the eruption of a long filament, centred around N20E30 that resulted in a slow CME observed around 10:00 UT on 30 October, with speed around 350 km/s and directed mostly towards the NE; but with a component close to the ecliptic. Then two CMEs erupted towards the north and NW quadrant around 13:00 UT on 30 October. Finally, a wide CME erupted towards the east first seen at 00:24 UT on 31 October by LASCO C2, this CME is backsided. Of these four CMEs, the first one has chances of arriving to the Earth, expected around 12:00 UT on 3 November. This is a slow and weak CME, which will most likely not create a significant geomagnetic impact.

Coronal holes

There are three positive polarity CHs in the western hemisphere. SIDC Coronal Hole 123 is the largest, located in the south. SIDC Coronal Hole 128 is smaller and located at the equator. Finally, SIDC Coronal Hole 129 has a considerable size and is located in the northern hemisphere.

Solar wind

The solar wind speed has increased under the influence of the HSS from SIDC Coronal Hole 123, combined with SIDC Coronal Hole 128 in the last 24 hours, reaching 750 km/s. The solar wind speed is currently at 630 km/s with an interplanetary magnetic field of 7 nT. We expect similar conditions to persist in the next 24 hours. After that, we can expect to see also the high speed solar wind from SIDC Coronal Hole 129, located in the northern hemisphere (also positive polarity). There is also a possible arrival, later on 1 November of the CME from 28 October (SIDC CME 589).

Geomagnetism

Geomagnetic conditions reached minor storm levels (Kp and K_Bel up to 5). In the next 24 hours, active to minor storm conditions can be expected. There is also a possible arrival, later on 1 November of the CME from 28 October (SIDC CME 589), but its impact is not expected to be significant.

Proton flux levels

The greater than 10 MeV GOES proton flux was below the 10 pfu threshold level over the past 24 hours and is expected to remain so for 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. The greater than 2 MeV electron flux is expected to increase above the 1000 pfu threshold over the next 24 hours. The 24-hour electron fluence was at normal levels and is expected to be at normal levels over the next 24 hours.

Today's estimated international sunspot number (ISN): 044, based on 15 stations.

Solar indices for 30 Oct 2025

Wolf number Catania	///
10cm solar flux	120
AK Chambon La Forêt	048
AK Wingst	041
Estimated Ap	041
Estimated international sunspot number	066 - Based on 18 stations

Noticeable events summary

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

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