Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2026 Apr 04 1240 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

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

	10cm flux	Ap
04 Apr 2026	134	017
05 Apr 2026	131	016
06 Apr 2026	128	010

Solar Active Regions and flaring

Solar flaring activity was moderate to high over the past 24 hours, with multiple M-class flares observed. The largest flare was an M7.5 flare (SIDC Flare 7328), peaking on 04 April at 01:17 UTC, originating from SIDC Sunspot Group 838 (NOAA Active Region 4409). Two additional M-class flares were recorded from the same region: an M1.7 flare (SIDC Flare 7334) peaking on 04 April at 07:58 UTC, and an M1.3 flare (SIDC Flare 7341) peaking on 03 April at 12:50 UTC. Several C-class flares were also observed. A total of seven numbered sunspot groups were present on the solar disk. SIDC Sunspot Group 838 (NOAA Active Region 4409), currently located near N02W05, exhibited a Beta-Gamma-Delta magnetic configuration and showed continued growth, remaining the most complex and active region on the disk. Solar flaring activity is expected to remained to moderate levels over the next 24 hours, with C-class flares expected and M-class flares likely, primarily from SIDC Sunspot Group 838 (NOAA Active Region 4409).

Espulsioni di massa coronale

A coronal mass ejections CME was observed on 02 April from SIDC Sunspot Group 835 (NOAA Active Region 4404, near N12W18), associated with an M3.5-class flare and a filament eruption occurring between approximately 16:00 and 21:00 UTC. This CME appeared narrow and was directed towards the northwest in SOHO/LASCO C2 imagery, and is not considered Earth-directed based on available observations. No additional Earth-directed coronal mass ejections were detected in available coronagraph imagery over the past 24 hours.

Fori coronali

SIDC Coronal Hole 142 (high-latitude coronal hole with a negative polarity) first reached the central meridian on April 03 and is now positioned on the western side of the Sun.

Vento solare

Solar wind parameters were strongly enhanced over the past 24 hours. A solar wind shock associated with the arrival of the interplanetary coronal mass ejection (SIDC CME 645) was observed on 03 April around 15:05 UTC. Solar wind speed increased abruptly from about 600 km/s to values up to approximately 850 km/s, and remained elevated thereafter, gradually decreasing to around 650-700 km/s. The interplanetary magnetic field (IMF) was enhanced, with the total field (Bt) reaching up to about 14 nT. The Bz component showed sustained variability with prolonged southward intervals reaching approximately -11 nT. These disturbed conditions occurred during the ongoing influence of a high-speed solar wind stream (HSS) originating from SIDC Coronal Hole 149 (an equatorial coronal hole with negative polarity that crossed the central meridian on 30 March). Solar wind conditions are expected to remain enhanced over the next 24 hours, with continued HSS influence and gradually declining ICME effects.

Geomagnetism

Geomagnetic conditions ranged from active to strong storm levels over the past 24 hours. Following the shock arrival in the solar wind condition, the global NOAA Kp index reached up to 7 (strong storm levels), while the local K index (Belgium) reached up to K=6 (moderate storm levels). The geomagnetic activity was driven by the combined effects of the ICME impact (SIDC CME 645) and the ongoing high-speed solar wind stream from SIDC Coronal Hole 149, together with sustained southward IMF conditions. Geomagnetic activity gradually decreased after the main phase, returning to unsettled to active levels towards the end of the period. Geomagnetic conditions are expected to remain unsettled to active over the next 24 hours, with possible isolated minor storm intervals depending on the evolution of the IMF Bz component.

Proton flux levels

The greater than 10 MeV proton flux remained below the event threshold (10 pfu) over the past 24 hours, with values generally below 7 pfu and showing a gradual decrease towards the end of the period. No proton event was observed. Higher energy channels (greater than 100 MeV and greater than 500 MeV) remained at background levels. STEREO-A (currently located at approximately 54 degrees longitude) also shows elevated proton flux, supporting the interpretation of a weak and likely far-sided source. The greater than 10 MeV proton flux is expected to remain below the event threshold over the next 24 hours. Further minor variations cannot be excluded, particularly due to the enhanced flaring activity currently ongoing from the complex region SIDC Sunspot Group 838 (NOAA Active Region 4409).

Electron fluxes at geostationary orbit

The greater than 2 MeV electron flux showed an initial enhancement to moderate levels, followed by a decrease to low levels around 04 April 02:00-04:00 UTC, likely associated with the main phase of the geomagnetic storm and magnetospheric depletion. A gradual recovery was observed thereafter, with fluxes returning to moderate levels and approaching the high flux threshold towards the end of the period. The 24-hour fluence remained at moderate levels throughout. Electron fluxes are expected to continue increasing over the next 24-48 hours due to the ongoing influence of the high-speed solar wind stream associated with SIDC Coronal Hole 149. High flux levels may be reached, with a corresponding increase in the fluence.

Today's estimated international sunspot number (ISN): 117, based on 15 stations.

Solar indices for 03 Apr 2026

Wolf number Catania	///
10cm solar flux	136
AK Chambon La Forêt	062
AK Wingst	041
Estimated Ap	045
Estimated international sunspot number	131 - Based on 17 stations

Noticeable events summary

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