Viewing archive of Wednesday, 28 May 2025

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2025 May 28 1241 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

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

	10cm flux	Ap
28 May 2025	140	031
29 May 2025	142	046
30 May 2025	145	029

Solar Active Regions and flaring

Solar flaring activity over the last 24 hours has been low. The largest flare was a C2.8 flare (SIDC Flare 4481) peaking on May 28 at 10:45 UTC, which was observed near the east limb. SIDC Sunspot Group 469 (NOAA Active Region 4100, magnetic type beta was responsible for most of the flaring activity, producing multiple C-class flares. SIDC Sunspot group 508 (NOAA Active region 4099, magnetic type beta-delta) also showed flux emergence and produced C-class flaring. SIDC Sunspot groups 482 and 506 (NOAA Active regions 4090 and 4098) have now rotated over the west solar limb. The other regions on disk were simple and mostly quiet. 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 Ejection (CME) directed to the north-east and first visible in SOHO/LASCO C2 imagery at 09:24 UTC on May 27 was likely associated with a long duration C5 flare (SIDC flare 4476). Initial analysis shows that this CME is not expected to be Earth directed.

Coronal holes

An extended mid-latitude to equatorial coronal hole (combined SIDC Coronal Hole 116 and 112) continues to transit the central meridian since May 26.

Solar wind

The solar wind conditions reflected the arrival of the high- speed stream associated with the small equatorial coronal hole that cross the central meridian on May 25. The solar wind speed increased from 400 km/s to a maximum of 640 km/s around 02:50 UTC May 28. The interplanetary magnetic field gradually increased reaching values of 16 nT by the end of the period. The Bz component ranged between -9 nT and 10 nT. The interplanetary magnetic field phi angle switched to the negative sector from 13:20 UTC May 27. Further enhanced solar wind conditions are expected over the next days due to the current high-speed stream and for the high- speed stream associated with SIDC Coronal Hole 116, which crossed the central meridian on May 26.

Geomagnetism

Geomagnetic conditions globally and locally reached Active conditions (NOAA Kp 4+, K BEL 4) over the past 24 hours. Active to Minor storm conditions expected over the next 24 hours with isolated intervals of moderate storm conditions possible, due to the ongoing and further expected high-speed stream effects.

Proton flux levels

The greater than 10 MeV proton flux was below the 10 pfu threshold over the past 24 hours. It is expected generally to remain below this threshold level over the next 24 hours, but a chance of an increase remains due to any high-level flaring activity from SIDC Sunspot Group 506 (NOAA Active Region 4098), which is located just beyond the west limb.

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux measured by GOES 18 crossed the 1000 pfu threshold briefly at 20:25 UTC on May 27. The greater than 2 MeV electron flux measured by GOES 19 was just below the 1000 pfu threshold. The greater than 2 MeV electron flux is expected to remain 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): 112, based on 18 stations.

Solar indices for 27 May 2025

Wolf number Catania	132
10cm solar flux	137
AK Chambon La Forêt	028
AK Wingst	///
Estimated Ap	016
Estimated international sunspot number	113 - Based on 19 stations

Noticeable events summary

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

All times in UTC

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