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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 May 04 1244 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

Quiet

	10cm flux	Ap
04 May 2025	154	012
05 May 2025	154	025
06 May 2025	154	015

Solar Active Regions and flaring

SIDC Sunspot Group 469 (NOAA Active Region 4079), currently located at N08E12, continues to exhibit a Beta- Gamma-Delta magnetic configuration and remained stable throughout the period. This region was the most active, producing approximately eight C-class flares, including the largest of the period, a C2.3 flare (SIDC Flare 4280) that peaked on May 3 at 14:09 UTC. Three additional sunspot groups were identified as growing: (1) SIDC Sunspot Group 490 (NOAA Active Region 4081) at N07E41, with a Beta configuration, (2) SIDC Sunspot Group 491 (NOAA Active Region 4080) at S12W79, with a Beta configuration, and (3) SIDC Sunspot Group 492 at S11E73, also with a Beta configuration. Given the complexity of Region 469 and the emergence of new regions, solar flaring activity is expected to remain moderate over the next 24 hours, with C-class flares likely and a continued chance for M-class flares.

Espulsioni di massa coronale

Several filaments are visible on the solar disk; however, they appear stable at this time. No Earth-directed coronal mass ejections (CMEs) were observed in the available coronagraph imagery over the past 24 hours.

Fori coronali

The trans-equatorial SIDC Coronal Hole 110 currently visible on the western side of the Sun, which first crossed the central meridian on May 1. It originated from SIDC Coronal Hole 110 (a high-latitude northern coronal hole with negative polarity) merged with SIDC Coronal Hole 109 (an equatorial coronal hole with negative polarity), forming the extended structure spanning both hemispheres. Meanwhile, SIDC Coronal Hole 111 (a high-latitude southern coronal hole with negative polarity) is approaching the central meridian and is expected to cross it tomorrow.

Vento solare

The Earth remains under the influence of a high-speed solar wind stream associated with SIDC Coronal Hole 99, a large trans-equatorial coronal hole with negative polarity, which reached the central meridian on April 29. Solar wind speeds were initially elevated, ranging between 800 and 870 km/s during the early part of the reporting period. Over time, speeds gradually decreased, reaching values near 500 km/s by the end of the interval. The interplanetary magnetic field (IMF) remained moderately strong, with total field strength (Bt) peaking at 8.6 nT. The southward component (Bz) fluctuated and being mostly negative, reaching as low as -7.3 nT, contributing to geomagnetic disturbances. The phi angle stayed in the negative sector, indicating ongoing magnetic connection to the source coronal hole, with negative polarity. Looking ahead, a brief period of calmer solar wind is expected before a possible second enhancement later today or early tomorrow, due to the influence of the merged trans- equatorial structure formed by SIDC Coronal Holes 109 and 110, which crossed the central meridian on May 1.

Geomagnetism

Geomagnetic conditions fluctuated between quiet and minor storm levels over the past 24 hours. The Kp-NOAA index reached 5- during a brief active period around 07:00-09:00 UTC on May 4, indicating a minor geomagnetic storm, while K_BEL peaked at 4. The remainder of the interval mostly showed unsettled to active conditions, with K-values between 3 and 4. This activity was driven by the continued impact of a high-speed solar wind stream associated with SIDC Coronal Hole 99, a large trans-equatorial coronal hole with negative polarity that crossed the central meridian on April 29. Looking ahead, unsettled conditions are expected to dominate, though isolated active periods remain possible. The influence of the current high-speed stream is waning, but another solar wind enhancement could arrive in later today or early tomorrow from the merged structure of SIDC Coronal Holes 109 and 110.

Proton flux levels

No enhancement or solar energetic particle event has been detected over the past 24 hours. 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 well above the threshold level over the past 24 hours, in response to the ongoing influence of high-speed solar wind streams. The 24-hour electron fluence also increased, reaching moderate levels, and is expected to remain at moderate levels over the next 24 hours. Elevated electron flux conditions are likely to persist as the high- speed stream continues to affect the near-Earth environment.

Today's estimated international sunspot number (ISN): 086, based on 15 stations.

Solar indices for 03 May 2025

Wolf number Catania	///
10cm solar flux	152
AK Chambon La Forêt	035
AK Wingst	028
Estimated Ap	030
Estimated international sunspot number	061 - Based on 24 stations

Noticeable events summary

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

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