Viewing archive of Saturday, 28 August 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Aug 28 1233 UTC

SIDC Forecast

Solar flares

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

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
28 Aug 2021	092	019
29 Aug 2021	091	010
30 Aug 2021	090	019

Bulletin

During last 24 the solar flaring activity significantly increased, with number of C-class and even one M-class flare reported. Although there are four active regions presently observed on the visible side of the Sun (NOAA ARs 2859, 2860, 2861 and 2862) majority of the flaring activity originated from the NOAA AR 2860 which presently has beta-gamma configuration of its photospheric magnetic field. In the coming hours we expect C-class flares but also M-class flares (in particular from NOAA AR 2860). The M4.7 flare, which originated from NOAA AR 2860, peaked at 06:11 UT on August 28. The flare was associated with the coronal dimming and EIT wave, the on disc signatures of the CME. There are presently only two available coronagraph images, and they show that associated CME is possibly partial halo which means that this CME could arrive to Earth. More will be reported when data become available.

The greater than 10 MeV proton flux was at background levels in the past 24 hours, and we expect it will remain so in the next 24 hours. The greater than 2 MeV electron flux crossed the 1000 pfu threshold during two intervals today, and it is presently still slightly above the threshold. The 24h electron fluence is at normal to moderate levels and we expect it will stay so in the coming 24 hours.

The solar wind speed is presently about 400 km/s and the interplanetary magnetic field magnitude is about 5 nT. The solar wind associated with two small, positive polarity coronal holes can still arrive 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 later today, but not very probable.

The in situ data show that, the arrival of the shock wave in the morning of August 27 was followed by arrival of its driver ICME. The continuously negative Bz component (down to - 15 nT) was observed during more than 20 hours, inducing disturbed geomagnetic conditions. Local station at Dourbes reported several long intervals of K=4 (starting at 12:00 UT yesterday until 06:00 UT today). NOAA reported long interval of Kp=4, lasting from 12:00 until 24:00 UT on August 27. After the midnight one interval of Kp=5 was reported, and from 06:00 to 09:00 UT NOAA reported Kp=4. Presently the geomagnetic conditions are unsettled and we expect them to stay so in the coming hours. However, the isolated intervals of active conditions are still possible.

Today's estimated international sunspot number (ISN): 073, based on 18 stations.

Solar indices for 27 Aug 2021

Wolf number Catania	068
10cm solar flux	090
AK Chambon La Forêt	038
AK Wingst	020
Estimated Ap	020
Estimated international sunspot number	067 - Based on 29 stations

Noticeable events summary

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

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