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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2021 Dec 22 1249 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

Quiet

	10cm flux	Ap
22 Dec 2021	135	008
23 Dec 2021	135	006
24 Dec 2021	132	011

Bulletin

Solar activity was at low to moderate levels over the past 24 hours with eleven C-class flares and a single M-class flare. There were ten numbered active regions on the visible disc including the newly numbered NOAA 2916 (alpha), responsible for the M-class flaring activity on Dec 20th and Dec 21st. Over the past 24 hours NOAA 2916 produced only C-class flaring, with the strongest one being C5.7, peak time 00:21 UTC on Dec 22nd. The most complex active region on the visible disk remains NOAA 2907 (beta-gamma), which produced four C-class flares, the strongest one being C4.9 (peak time 22:43 on Dec 22nd). The neighbouring region NOAA 2908 (beta) increased its number of sun spots and produced three C-class flares and an M1.3-class flare (start time 06:54 UTC, end time 07:21 UTC and peak time 07:06 UTC on Dec 22nd). NOAA 2909 produced a single C-class flare (C4.9 with peak time 19:23 UTC on Dec 21st) and decreased its magnetic type from beta to alpha. Previous active region NOAA 2906 (alpha) has rotated towards the west limb and decayed into a plage. NOAA 2910, currently at the west limb, has increased its magnetic type from alpha to beta and is expected to rotated over the limb within the next 24 hours. Two other active region have been numbered, namely NOAA 2914 and NOAA 2915, both estimated to have photospheric magnetic type alpha. The X-ray flare activity is expected to be at low to moderate levels for the next 24 hours with remaining high probability for isolated M-class flaring.

The C4.9-class flare produced by NOAA 2909 (peak time 19:23 UTC on Dec 21st) was followed by a coronal dimming and signatures of eruption. Yet, currently no Earth-directed CMEs are detected in the available coronagraph imagery. The M1.3-class flare produced by NOAA 2908, peak time 07:06 UTC on Dec 22nd, might also be followed by an eruption. More analysis will be performed as chronograph data for this time 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. Minor enhancements remain possible in case of significant M-class flaring. The greater than 2MeV electron flux was under the 1000 pfu threshold and is expected to exceed the 1000 pfu threshold over the next 24 hours. The 24h electron fluence was at nominal levels and is expected to reach moderate levels in the next 24 hours.

Over the past 24 hours all solar wind parameters (ACE and DSCOVR) remained under the influence of a high-speed stream (HSS). The solar wind velocity was rather steady around 570 km/s with minor fluctuations in the range of 525 km/s to 600 km/s. The interplanetary magnetic field was predominantly at background levels with values between 3 nT and 6.3 nT. The Bz-component varied in between -4.6 to 5.8 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 for the rest of the day under the persisting influence of the HSS and start a slow return towards background solar wind conditions after.

The geomagnetic conditions over the past 24 hours were quiet to unsettled. Mostly quiet to unsettled geomagnetic conditions are expected for the next 24 hours. Isolated active periods remain possible, but unlikely.

Today's estimated international sunspot number (ISN): 150, based on 12 stations.

Solar indices for 21 Dec 2021

Wolf number Catania	164
10cm solar flux	137
AK Chambon La Forêt	013
AK Wingst	011
Estimated Ap	011
Estimated international sunspot number	128 - Based on 24 stations

Noticeable events summary

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

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