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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 May 01 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
01 May 2025	148	025
02 May 2025	148	032
03 May 2025	148	007

Solar Active Regions and flaring

Solar flaring activity was low over the past 24 hours, with only C-class flares detected. The total number of sunspot groups has also decreased, with only five currently visible on the solar disk. SIDC Sunspot Group 476 (NOAA Active Region 4065) has now rotated over the western limb, while SIDC Sunspot Groups 480 (NOAA 4068) and 485 (NOAA 4077) have shown signs of decay. The most active region is SIDC Sunspot Group 469 (NOAA Active Region 4079), currently located at N09E52. This region has a Beta magnetic configuration, showed signs of growth over the past 24 hours, and produced the largest flare of the period: a C2.5 flare (SIDC Flare 4255), which peaked on May 1 at 07:19 UTC. The remaining sunspot groups did not produce any flaring activity. Solar flaring activity is expected to remain low over the next 24 hours, with C-class flares very likely and only a small chance of M-class flares.

Espulsioni di massa coronale

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

Fori coronali

SIDC Coronal Hole 99, a mid-latitude coronal hole with negative polarity, first reached the central meridian on April 29 and is now positioned on the western side of the Sun. The associated high-speed solar wind stream is currently arriving at Earth. Two small coronal holes reached the central meridian today, May 1: SIDC Coronal Hole 109, an equatorial coronal hole with negative polarity, and SIDC Coronal Hole 110, a high-latitude coronal hole also with negative polarity.

Vento solare

The Earth remains under the influence of a slow solar wind, with speeds ranging between 400 and 490 km/s. The total interplanetary magnetic field (IMF) showed some enhancement and fluctuated throughout the period, reaching values up to 11.7 nT. The southward component of the IMF (Bz) was mainly positive on April 30, then turned negative on May 1, reaching a minimum of -9.8 nT. Around 01:00 UTC on May 1, the phi angle switched from positive to negative polarity. This transition is likely an early indicator of the arrival of the high-speed stream originating from the trans-equatorial coronal hole with negative polarity, the SIDC Coronal Hole 99, which crossed the central meridian on April 29. Solar wind speed is expected to increase later today and into tomorrow. The Earth is likely to come under the influence of this high-speed stream over the next few days.

Geomagnetism

Geomagnetic conditions were quiet to unsettled until early May 1, around 00:00 UTC, when they reached active levels, with Kp-NOAA and K_BEL both peaking at 4. This increase in activity was driven by an enhanced interplanetary magnetic field (IMF) and the southward turning of its Bz component, which reached a minimum of -9.8 nT and remained negative for the extended period. With the expected 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), the geomagnetic conditions may intensify further. Minor storm to storm levels are possible later today and tomorrow, before gradually returning to unsettled conditions, with occasional active periods expected until the influence of the high-speed stream subsides.

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): 070, based on 19 stations.

Solar indices for 30 Apr 2025

Wolf number Catania	113
10cm solar flux	148
AK Chambon La Forêt	019
AK Wingst	012
Estimated Ap	012
Estimated international sunspot number	088 - Based on 47 stations

Noticeable events summary

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

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