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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Apr 30 1232 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

Quiet

	10cm flux	Ap
30 Apr 2025	150	010
01 May 2025	150	011
02 May 2025	150	022

Solar Active Regions and flaring

Solar flaring activity was moderate over the past 24 hours, with one M-class flare observed. A total of eight numbered sunspot groups were identified on the solar disk during this period. SIDC Sunspot Group 455 (NOAA Active Region 4078), located at N15W65 and previously responsible for several M-class flares, has since decayed and now shows a simple Alpha magnetic configuration. The largest flare of the period was an M2.0 event (SIDC Flare 4244), which peaked on April 30 at 07:51 UTC. It originated from the returning SIDC Sunspot Group 469 (NOAA Active Region 4079, formerly numbered 4055). This region also produced several C-class flares and is expected to remain active in the coming days. Although SIDC Sunspot Group 484 (NOAA Active Region 4072), currently located at S19W20, is the most magnetically complex region on the disk (with a Beta-Gamma configuration) it did not exhibit any flaring activity over the past 24 hours. Solar flaring activity is expected to be low to moderate over the next 24 hours, with C-class flares very likely and a chance for isolated M-class flares.

Espulsioni di massa coronale

No coronal mass ejections (CMEs) were observed in the available coronagraph imagery over the past 24 hours.

Fori coronali

The recurrent SIDC Coronal Hole 99, a large trans-equatorial elongated coronal hole with negative polarity, reached the central meridian on April 29. This structure was previously observed crossing the central meridian on April 6. SIDC Coronal Hole 60, a mid-latitude coronal hole with positive polarity, reached the central meridian on April 30 and is now positioned on the western side of the Sun. It closely followed SIDC Coronal Hole 104, located at a similar latitude. This particular coronal hole (SIDC CH 60) is a well-established recurrent feature, with previous central meridian crossings recorded from September 13.

Vento solare

The Earth remains under the influence of a slow solar wind, with speeds ranging between 400 and 460 km/s. The total interplanetary magnetic field (IMF) gradually increased and peaked at 10.0 nT around April 29 at 22:30 UTC, before returning to values near 6 nT. The southward component of the IMF (Bz) was predominantly positive during the earlier part of the period but turned negative around April 29 at 22:30 UTC, reaching a minimum of -7.6 nT. These minor perturbations could possibly be attributed to the mild influence of a high-speed stream linked to the positive polarity coronal holes located in the southern hemisphere (SIDC Coronal Holes 104 and 60). Slow solar wind conditions are expected to persist over the next 24 hours. However, in approximately two days, the arrival of a high-speed stream is anticipated from SIDC Coronal Hole 99, a large, elongated trans-equatorial coronal hole with negative polarity, which crossed the central meridian on April 29.

Geomagnetism

Geomagnetic conditions reached active levels (Kp-NOAA = 4 and K_BEL = 3), in response to the southward interplanetary magnetic field (Bz component) remaining negative for an extended period around April 29 at 22:30 UTC. Outside of this interval, geomagnetic conditions were mostly quiet to unsettled. Quiet to unsettled conditions are expected to continue over the next 24 hours. However, beginning around May 2, geomagnetic activity may increase, potentially reaching minor storm to storm levels due to the anticipated arrival of a high-speed solar wind stream associated with SIDC Coronal Hole 99 (a large, elongated trans-equatorial coronal hole with negative polarity that crossed the central meridian on April 29). During its previous rotation, this structure produced geomagnetic activity with Kp values reaching up to 6.

Proton flux levels

No enhancement or solar energetic particle event has been detected. The greater-than-10 MeV proton flux remained at low levels over the past 24 hours and is expected to stay below the event threshold in the next 24 hours.

Electron fluxes at geostationary orbit

The greater-than-2 MeV electron flux measured by GOES 18 and GOES 19 remained below the threshold level over the past 24 hours. The flux is expected to remain below the threshold over the next 24 hours. The 24-hour electron fluence remained at normal levels and is anticipated to stay stable.

Today's estimated international sunspot number (ISN): 086, based on 29 stations.

Solar indices for 29 Apr 2025

Wolf number Catania	138
10cm solar flux	149
AK Chambon La Forêt	014
AK Wingst	007
Estimated Ap	006
Estimated international sunspot number	110 - Based on 38 stations

Noticeable events summary

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

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