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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2021 Dec 21 1252 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

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

Protoni solari

Quiet

	10cm flux	Ap
21 Dec 2021	127	008
22 Dec 2021	125	007
23 Dec 2021	125	006

Bulletin

Solar activity was at moderate levels over the past 24 hours with thirteen C-class flares and two impulsive M-class flares from a new active region rotating from behind the east limb (near S17E89). There are nine numbered active regions on the visible disc, namely NOAA 2906 to NOAA 2913. The most prominent complex region currently is NOAA 2907 (beta-gamma), which produced five of the C-class flares, including a C5.5 (peak time 01:57 on Dec 21st). NOAA 2908 (beta) produced three C-class flares, including a C4.9 (peak time 07:22 on Dec 21st). NOAA 2909 (beta) remained stable and quiet and all the other numbered active regions have simple alpha photospheric magnetic field configuration and have remained stable, with the exception of NOAA 2910, which produced a single C1.6-class flare. A new active region emerged from the east limb and produced three C-class flares, an M1.1 (peak time at 07:50 UTC on Dec 21th) and M1.4-class flare (peak time at 11:44 UTC on Dec 21th). The X-ray flare activity is expected to be at moderate levels for the next 24 hours with high probability for M-class flaring mainly from the newly rotated active region on the east limb.

A faint and slow partial halo coronal mass ejection (CME) lifted off the solar surface around midday on Dec 20th following the M1.9-class impulsive flare from NOAA 2908. The estimated projected speed of the CME is 330 km/s and a glancing blow from it is expected to reach the Earth in the late afternoon on Dec 24th. No other Earth-directed coronal mass ejections (CMEs) were observed in available coronagraph imagery.

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 with possible minor increase in case of significant M-class flaring. The greater than 2MeV electron flux was under the 1000 pfu threshold and is expected to remain so for the next 24 hours. The 24h electron fluence was at nominal levels and is expected to remain mostly at nominal levels, but to start increasing towards moderate levels in the next 24 hours.

Over the past 24 hours all solar wind parameters (ACE and DSCOVR) continued to be under the influence of a high-speed stream (HSS). The solar wind velocity has significantly increased varying in the range of 490 to 689 km/s. The interplanetary magnetic field was predominantly at background values with am isolated maximum of 8.5 nT. The Bz-component varied in between -7.11 to 7.11 nT. The polarity of the magnetic field remained predominantly in the negative sector (directed towards the Sun). The solar wind parameters are expected to remain enhanced over the next 24 hours under the persisting influence of the HSS.

The geomagnetic conditions over the past 24 hours were globally quiet to active, while locally in Belgium only quiet to unsettled geomagnetic conditions were registered. Quiet to active geomagnetic conditions are expected for the next 24 hours with remaining possibility for isolated minor storms, depending on the Bz strength and orientation.

Today's estimated international sunspot number (ISN): 128, based on 13 stations.

Solar indices for 20 Dec 2021

Wolf number Catania	133
10cm solar flux	123
AK Chambon La Forêt	022
AK Wingst	016
Estimated Ap	016
Estimated international sunspot number	119 - Based on 17 stations

Noticeable events summary

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

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