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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2025 Apr 21 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
21 Apr 2025	156	040
22 Apr 2025	156	026
23 Apr 2025	156	011

Solar Active Regions and flaring

A total of 7 numbered sunspot groups were identified on the disk over the past 24 hours. SIDC Sunspot Group 473 (NOAA Active Region 4062) currently located at S03W04 is the most complex one, with a Beta-Gamma magnetic configuration, it was stable over the past 24 hours. The largest flare was a C4.3 flare (SIDC Flare 4161) peaking on April 20 at 17:18 UTC, which was produced by SIDC Sunspot Group 475 (NOAA Active Region 4063). 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 CME was seen first at 21:48 UTC on April 20 by LASCO C2. It originated from a filament eruption close to the NW limb, with angular width around 70 degrees, it is not expected to arrive to the Earth. No Earth-directed CMEs were observed in the available coronagraph imagery in the last 24 hours.

Fori coronali

There is a large positive polarity coronal hole (SIDC Coronal Hole 104) covering a large area of the southern hemisphere.This is a recurrent coronal hole, in the previous rotation it had a more developed equatorial extension.

Vento solare

The Earth is under the influence of a high speed solar wind stream from the large positive polarity coronal hole in the southern hemisphere (SIDC Coronal Hole 104). The solar wind speed has reached 650 km/s (measured by ACE) and is still increasing, the interplanetary magnetic field has reached 19 nT (currently around 12 nT) with Bz down to -13 nT (currently positive).During the previous solar rotation, this same coronal hole produced solar wind speeds approaching 900 km/s at Earth. However, this time the coronal hole's equatorial extension is less developed, which may result in slightly lower wind speeds. Nonetheless, the solar wind speed is expected to be high in the next 24 hours.

Geomagnetism

Geomagnetic conditions have reached active levels both locally and planetary (K_Bel and Kp up to 4). Due to the effect of the high speed solar wind stream, minor storm levels can be expected (K up to 5), with moderate storms possible (K up to 6).

Proton flux levels

The greater than 10 MeV proton flux was below the threshold level over the past 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 was reaching threshold values between 21:00 UTC and 22:00 UTC on April 20. The greater than 2 MeV electron flux measured by GOES 19 was below the threshold over the past 24 hours. The greater than 2 MeV electron flux is expected to remain below the threshold over the next 24 hours. The 24-hour electron fluence is presently at normal levels and is expected to remain so over the next 24 hours.

Today's estimated international sunspot number (ISN): 131, based on 11 stations.

Solar indices for 20 Apr 2025

Wolf number Catania	///
10cm solar flux	156
AK Chambon La Forêt	021
AK Wingst	014
Estimated Ap	014
Estimated international sunspot number	125 - Based on 18 stations

Noticeable events summary

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

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