Viewing archive of Friday, 27 August 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Aug 27 1259 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

Active conditions expected (A>=20 or K=4)

Solar protons

Quiet

	10cm flux	Ap
27 Aug 2021	093	016
28 Aug 2021	090	014
29 Aug 2021	088	010

Bulletin

There are presently three numbered sunspot groups observed on the visible side of the Sun, Catania sunspot groups 32 and 33 (NOAA ARs 2860 and 2859) and NOAA AR 2861, which still does not have Catania number. All three groups have presently beta configuration of their photospheric magnetic field and were source of the flaring activity in the past 24 hours (three C-class and a number of B-class flares). We can expect B-class and C-class flares in the coming hours. The long duration C3.0 flare (peaked at 18:18 UT on April 26) which originating from the Catania sunspot group 33 (NOAA AR 2859), was associated with the coronal dimming, EIT wave and the halo CME. The CME was first observed in the SOHO LASCO C2 field of view at about 19:00 UT on April 26. It had angular width of about 290 degrees and projected line of the sight speed of about 530 km/s (as reported by the CACTUS software). This CME might arrive to Earth in the morning of August 30.

The greater than 10 MeV proton flux is at the background levels, the greater than 2 MeV electron flux is bellow the 1000 pfu threshold, and the 24h electron fluence is at normal level. We do not expect significant change in the values of these three parameters in the coming hours.

The in situ data indicated arrival of the shock wave, most probably associated with the expected arrival of the partial halo CME (first observed in the SOHO LASCO C2 field of view at about 06:00 UT on August 23rd). The sudden increase of the solar wind speed, density, temperature and interplanetary magnetic field magnitude was observed at about 00:25 UT on August 27. The solar wind speed is presently about 420 km/s and the interplanetary magnetic field magnitude is about 7 nT.

The solar wind associated with the two small, positive polarity coronal holes (they crossed central meridian in the early morning of August 24) can be expected later today. Glancing blow associated with the CME (first observed in the SOHO/LASCO C2 field of view at 06:36 UT on August 24) is possible on August 28, but not very probable. The arrival of the shock wave, early this morning, induced only unsettled geomagnetic conditions. During last 24 hours the geomagnetic conditions were at quiet to unsettled level. We expect such a geomagnetic conditions to prevail in the coming hours. However, the isolated intervals of active geomagnetic conditions (due to the arrival of the CME and the solar wind from the positive polarity coronal holes) are possible.

Today's estimated international sunspot number (ISN): 067, based on 25 stations.

Solar indices for 26 Aug 2021

Wolf number Catania	///
10cm solar flux	089
AK Chambon La Forêt	010
AK Wingst	006
Estimated Ap	006
Estimated international sunspot number	043 - Based on 26 stations

Noticeable events summary

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

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