Viewing archive of Thursday, 22 April 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Apr 22 1231 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

Quiet (A<20 and K<4)

Solar protons

Quiet

	10cm flux	Ap
22 Apr 2021	080	005
23 Apr 2021	079	011
24 Apr 2021	078	008

Bulletin

During last 24 hours number of B-class and seven C-class flares were reported. Majority of the C-class flares originated from the Catania sunspot group 86 (NOAA AR 2817). The C3.8 and C2.7 flares (peaked at 04:35 UT and 05:06 UT on April 22) originated from the Catania sunspot group 87 (NOAA AR 2816) presently situated at the center of the solar disc. We expect this level of the flaring activity to persist in the coming hours. The C-class flares are expected and M-class flares are possible, but not very probable. The C3.8 flare was associated with very faint partial halo CME, having the angular width of about 160 degrees. Due to the data gap presently only one image of the CME is available which does not allow us to estimate the CME speed. Since the source region of this wide CME was situated very close to the disc center we might expect that CME will arrive at Earth. When more observations become available, the forecasted CME arrival time will be communicated.

The greater than 2MeV electron flux is 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.

The solar wind speed is slowly decreasing during last 48 hours and its present values is about 420 km/s. The interplanetary magnetic field magnitude is about 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 starting from the morning of April 23. 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): 043, based on 26 stations.

Solar indices for 21 Apr 2021

Wolf number Catania	049
10cm solar flux	078
AK Chambon La Forêt	008
AK Wingst	006
Estimated Ap	006
Estimated international sunspot number	043 - Based on 32 stations

Noticeable events summary

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

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