Viewing archive of Wednesday, 25 August 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Aug 25 1232 UTC

SIDC Forecast

Solar flares

Quiet conditions (<50% probability of C-class flares)

Geomagnetism

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

Solar protons

Quiet

	10cm flux	Ap
25 Aug 2021	082	012
26 Aug 2021	081	013
27 Aug 2021	081	013

Bulletin

There are presently two named sunspot groups observed on the visible side of the Sun, Catania sunspot group 33 (NOAA AR 2859) and Catania group 32 (NOAA AR 2860) that just rotated across the East solar limb. Both of these sunspot groups were sources of a few low C-class and B-class flares which were associated with narrow CMEs. The newly arrived data show that the CME associated with a large filament eruption, and first observed in the SOHO/LASCO C2 field of view at 06:36 UT on August 24 had velocity of about 450 km/s and the angular width of about 100 degrees. Glancing blow associated with that CME is possible (in August 28) but not very probable.

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.

Early this morning the increase of the interplanetary magnetic field magnitude was observed (up to 9nT) simultaneously with the solar wind speed (up to 400 km/s) and the temperature increase. It is possible that this is the compression region in front of the expected fast solar wind, originating from the northern polar coronal hole extension. However, the interplanetary magnetic field magnitude already decreased to value of 5 nT and the solar wind velocity is about 360 km/s. Two small positive polarity coronal holes (one equatorial and second centered around 30 degrees on the Southern solar hemisphere) crossed central meridian in the early morning of August 24. The associated solar wind can be expected at Earth late tomorrow or in the morning of August 27. During last 24 hours the geomagnetic conditions continued to be at quiet to unsettled level. We expect such a geomagnetic conditions to prevail in the coming hours. However, the arrival of the solar wind from the coronal hole followed by the expected arrival of the halo CME in the afternoon or in the evening of August 26 could induce active geomagnetic conditions.

Today's estimated international sunspot number (ISN): 031, based on 23 stations.

Solar indices for 24 Aug 2021

Wolf number Catania	027
10cm solar flux	081
AK Chambon La Forêt	012
AK Wingst	007
Estimated Ap	005
Estimated international sunspot number	018 - Based on 33 stations

Noticeable events summary

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

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