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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2021 Apr 23 1230 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

Quiet

	10cm flux	Ap
23 Apr 2021	080	010
24 Apr 2021	081	008
25 Apr 2021	080	011

Bulletin

Numerous B-class and C-class flares were reported during last 24 hours. All the flaring activity originated from the two sunspot groups Catania groups 86 and 87 (NOAA AR 2817 and NOAA AR 2816). Presently Catania sunspot group 86 (NOAA AR 2817) is rotating over the West solar limb, which will somewhat decrease the reported flaring activity. However, we can still expect B-class and C-class flares in the coming hours, originating mostly from Catania sunspot group 87 (NOAA AR 2816). M-class flares are possible but not very probable. Faint and slow partial halo CME (reported yesterday), was first seen in the SOHO LASCO C2 field of view at about 06:12 UT on April 22. The CME had angular width of about 160 degrees and projected line of the sight speed of about 450 km/s (as reported by CACTUS software). The CME was Earth directed and we might expect its arrival late evening on April 25. There were no other Earth directed CMEs during last 24 hours. During last 24 hours the proton flux levels remained at background level.

The greater than 2MeV electron flux is still above the 1000 pfu threshold, and it is expected to remain so in the coming 24 hours. The 24h electron fluence is at moderate to high level and is likely it will stay so in the next 24 hours.

Earth is presently inside the slow solar wind (speed of about 390 km/s), and the interplanetary magnetic field magnitude is 4 nT. The solar wind originating from the small, negative polarity equatorial coronal hole (reached central meridian in the morning of April 20), can be expected at Earth in the coming hours. During last 24 hours geomagnetic conditions were quiet. We expect quiet to unsettled geomagnetic conditions in the coming hours.

Today's estimated international sunspot number (ISN): 033, based on 27 stations.

Solar indices for 22 Apr 2021

Wolf number Catania	///
10cm solar flux	084
AK Chambon La Forêt	014
AK Wingst	006
Estimated Ap	005
Estimated international sunspot number	043 - Based on 36 stations

Noticeable events summary

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

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