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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2021 Dec 20 1251 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

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

Protoni solari

Quiet

	10cm flux	Ap
20 Dec 2021	125	018
21 Dec 2021	118	019
22 Dec 2021	118	009

Bulletin

Solar activity was at moderate levels over the past 24 hours with 11 C-class flares and an impulsive M1.9-class flare with peak time at 11:30 UTC on Dec 20th. There are eight numbered active regions (ARs) on the visible disc. The most prominent of which are NOAA 2907 (beta-gamma), which produced the majority of the C-class flaring, NOAA 2908 (beta), which produced two C-class flares and was responsible for the M-class flaring, and NOAA 2909 (beta), which produced an impulsive C4.4-class flare (with peak time at 03:21 UTC on Dec 20th). Several unnumbered active regions have emerged in the north-east and the south-east, which currently seem faint and show no signs of flaring activity. The X-ray flare activity is expected to be at low to moderate levels for the next 24 hours with increasing chances for M-class flaring.

No Earth-directed coronal mass ejections (CMEs) were observed in available coronagraph imagery. A type II radio burst and coronal dimming associated with the M-class flare suggest an eruption with possibly Earth-directed component, but this remains to be analysed as coronagraph data becomes available.

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 due to the recent M1.9-class flare. 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 at nominal levels in the next 24 hours.

Over the past 24 hours all solar wind parameters (ACE and DSCOVR) have registered the arrival of a high-speed stream. The solar wind velocity increased from 343 to 578 km/s. The interplanetary magnetic field reached a peak of 23 nT around 20:40 UTC on Dec 19th with a minimum Bz of -21 nT. Those enhanced values of the magnetic field lasted for a short period and the current magnitude of the interplanetary B field is below 8 nT. The B field was predominantly in the negative sector (directed towards the Sun). The solar wind parameters are expected to remain enhanced over the next 24 hours and the solar wind speed might increase further with the arrival of the high speed stream of another negative polarity coronal hole.

The geomagnetic conditions over the past 24 hours registered quiet to minor storm levels. Globally the geomagnetic conditions were predominantly active with an isolated minor storm interval between 21 UTC and midnight on Dec 19th. Locally minor storm levels were registered between 18 and 20 UTC and at 21 UTC on Dec 19th. Mostly unsettled to active geomagnetic conditions are expected for the next 24 hours with a possibility for more isolated minor storms.

Today's estimated international sunspot number (ISN): 116, based on 09 stations.

Solar indices for 19 Dec 2021

Wolf number Catania	///
10cm solar flux	115
AK Chambon La Forêt	028
AK Wingst	018
Estimated Ap	018
Estimated international sunspot number	108 - Based on 12 stations

Noticeable events summary

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

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