Viewing archive of Tuesday, 28 December 2021

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2021 Dec 28 1231 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
28 Dec 2021	122	011
29 Dec 2021	120	029
30 Dec 2021	120	011

Bulletin

Solar activity was dominated by NOAA active region 2918 (Catania group 96) which produced several C flares as well as the largest flare of the period, an M1.8 flare peaking at 4:01UT. The region saw renewed magnetic flux emergence in the leading area. Region 2919 (Catania group 98) remained unipolar and the bipolar region 2920 (Catania group 93) remained quiet and seemed to shrink and simplify. Bipolar region 2916 (Catania group 97) also remained quiet but remains the largest region on disc. Of the developing region in the North-West only one consolidated into a small bipolar region (Catania group 94). Overall, C class flaring must be expected with a small chance for further M flares.

On disc signatures suggest that the M1.8 flare was associated with a CME but this is not (yet) visible in coronagraph data. No other Earth directed CMEs have been observed in coronagraph data.

The greater than 10 MeV proton flux was at nominal levels in the past 24 hours and is expected to remain so in the next 24 hours. The greater than 2MeV electron flux remained under the 1000 pfu threshold following yesterdays shock arrival. The 24h electron fluence was at normal levels and is expected to be at normal levels over the next 24 hours. With the ongoing high speed stream conditions a renewed rise in electron fluxes is expected in the next days.

Solar wind conditions showed the expected increase in Solar wind speed reaching currently over 500 km/s. The magnetic field magnitude peaked early in the period to over 15nT and remained elevated most of the period in the 8-10nT range. Bz was variable and the magnetic field phi angle was indicative of connection to a positive polarity sector. Solar wind conditions will continue in this regime and may see a renewed elevation, tomorrow, when connection switches to the equatorial positive polarity coronal hole. Solar wind speed is then expected to rise further.

Geomagnetic conditions were active at the start of the period (NOAA Kp and local K Belgium reaching 4 just after noon) but then eased to quiet to unsettled. Further active conditions are possible. From tomorrow, there is also a chance for minor geomagnetic storms resulting from the continued and renewed elevated Solar wind conditions.

Today's estimated international sunspot number (ISN): 102, based on 12 stations.

Solar indices for 27 Dec 2021

Wolf number Catania	127
10cm solar flux	124
AK Chambon La Forêt	018
AK Wingst	012
Estimated Ap	011
Estimated international sunspot number	106 - Based on 13 stations

Noticeable events summary

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

All times in UTC

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