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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2026 May 27 1231 UTC

SIDC Forecast

Brillamenti solari

C-class flares expected, (probability >=50%)

Geomagnetism

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

Protoni solari

Quiet

	10cm flux	Ap
27 May 2026	146	008
28 May 2026	149	020
29 May 2026	151	011

Solar Active Regions and flaring

Solar flaring activity has been low over the past 24 hours, with few C-class flares. The strongest flare was C9.7 flare (SIDC Flare 7783) peaking at 12:38 UTC on May 26, associated with SIDC Sunspot Group 876 (previously NOAA Active Region 4451, magnetic type beta). There are currently fourteen numbered active regions on the solar disk. The most complex ones have a beta magnetic configuration. SIDC Sunspot Group 882 has decayed into plage. Returning SIDC Sunspot Groups 856 and 860 (both with magnetic type alpha) have rotated on disk from the east limb. SIDC Sunspot Group 883 (magnetic type beta) has emerged in the northwest quadrant. The solar flaring activity is expected to be low over the next 24 hours, with C-class flares very likely and a chance for M-class flares.

Espulsioni di massa coronale

A slow partial halo Coronal Mass Ejection (SIDC CME 660) was partially observed in LASCO/C2, LASCO/C3 and STEREO-A coronagraph imagery, starting from 13:30 UTC on May 26. The bulk of the ejecta is propagating to the south with an estimated projected speed of around 280-300 km/s. It is most likely a backsided event and it is not expected to impact Earth. No other Earth-directed CMEs were observed in the available coronagraph imagery during the last 24 hours.

Fori coronali

A northern, mid-latitude, negative polarity coronal hole (SIDC Coronal Hole 142) is crossing the central meridian. A mild associated high-speed stream may arrive at Earth starting from the UTC evening on May 29.

Vento solare

Over the last 24 hours, the solar wind parameters (ACE and DSCOVR) reflected mostly slow solar wind conditions. The solar wind speed varied between 390 km/s to 450 km/s. The interplanetary magnetic varied between 5 nT and 9 nT and the Bz component between -7 nT and 7 nT. The interplanetary magnetic field angle phi was predominantly in the negative sector. Slow solar wind conditions are expected initially over the next 24 hours, with a chance for enhanced conditions later due to the possible arrival of a mild high-speed stream from the southern, negative polarity coronal hole (SIDC Coronal Hole 149).

Geomagnetism

Geomagnetic conditions globally were mostly quiet (NOAA Kp 1-2) during the last 24 hours, with an interval of active conditions (NOAA Kp 4) between 21:00 UTC on May 26 and 00:00 UTC on May 27. Geomagnetic conditions locally were quiet to unsettled (K Bel 2 to 3) during the last 24 hours. Unsettled to active conditions (NOAA Kp 3 to 4), with a chance for isolated minor storm intervals (NOAA Kp 5) are expected over the next 24 hours, due to the possible arrival of a mild high-speed stream from the southern, negative polarity coronal hole (SIDC Coronal Hole 149).

Proton flux levels

The greater than 10 MeV proton flux has decreased below the 10 pfu threshold during the last 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. The 24-hour electron fluence was at normal levels and it is expected to remain so over the next 24 hours.

Today's estimated international sunspot number (ISN): 179, based on 25 stations.

Solar indices for 26 May 2026

Wolf number Catania	222
10cm solar flux	141
AK Chambon La Forêt	013
AK Wingst	010
Estimated Ap	008
Estimated international sunspot number	157 - Based on 26 stations

Noticeable events summary

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

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