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Daily bulletin on solar and geomagnetic activity from the SIDC

Випущено: 2021 Nov 02 1248 UTC

SIDC Forecast

Сонячні спалахи

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

Geomagnetism

Moderate (ISES: Major) magstorm expected (A>=50 or K=6)

Сонячні протони

Warning condition (activity levels expected to increase, but no numeric forecast given)

	10cm flux	Ap
02 Nov 2021	098	028
03 Nov 2021	097	034
04 Nov 2021	095	087

Bulletin

The largest flare of the period was an M1.7 flare peaking at 3:01UT from NOAA active region 2891, with an associated dimming visible in EUV images. NOAA region 2887 produced only C flares, but both the C1.3 flare peaking at 18:01 and the C4.4 flare peaking at 21:58 were associated with CME's. NOAA active region 2891 is now the most complex region on disc, with opposite field concentrations near the trailing spot. NOAA active region 2887 continued its decay and seems to have lost its trailing spots. The new region in the North-East (NOAA 2893) is unipolar and insignificant.

The C1.3 as well as the C4.4 flare from NOAA active region 2887 both had associated CMEs visible in SoHO LASCO C2 coronagraph images, mostly directed towards the South-West. They are visible from 18:24UT and 21:36UT respectively. A filament eruption from the North-Western quadrant further adds to these CME coronagraph signatures. From all these, the most significant is the eruption associated to the C4.4 flare, of which the CME has angular width between 150 and 180 degrees, and a projected speed of around 700 km/s. A glancing blow from that one cannot be excluded but will most probably not be separable from the more likely arrivals of the November 1 2:00UT CME (arrival early November 4) and the CME from NOAA region 2891 (see next paragraph)

SoHO LASCO C2 coronagraph images show an asymmetric full halo CME from 2:48UT onwards, associated to the M1.7 flare from NOAA active region 2891. Its speed projected on the plane of the sky is around 650 km/s on average with larger speeds of around 1100km/s in the Northern direction. STEREO COR2 coronagraph images are currently not (yet) available to provide better 3D velocity estimates. The CME is certainly Earthbound and an arrival can preliminarily be estimated to be in the late hours of November 4, but this will be refined later as more data become available.

The more than 10MeV proton flux remained slightly enhanced but below the event threshold. A further gentle decay is expected but there remains some possibility of a proton event. The greater than 2 MeV electron flux was below the 1000 pfu threshold. The 24h electron fluence is at low to nominal levels and expected to remain so initially.

Solar wind conditions became elevated due to a high speed stream associated to the southern extension of the northern polar coronal hole. Solar wind speed slowly increased from around 450 km/s at the start of the period to now just over 600 km/s. Interplanetary magnetic field magnitude reached 15nT in the compression region, but Bz remained mostly positive. Interplanetary magnetic field is now back at a nominal 5nT. The magnetic field orientation indicated connection with a positive polarity sector. Solar wind is expected to remain enhanced over the next 24-48 hours although the Soalr wind speed is not expected to rise further. By November 4 further or new enhancements must be expected due to a series of CMEs.

Geomagnetic conditions became active due to the high speed stream conditions and are expected to remain unsettled to active with a decreasing trend over the next 24-48 hours. On November 4 with the arrival of a series of CME's minor to moderate geomagnetic storming must be anticipated.

Today's estimated international sunspot number (ISN): 043, based on 14 stations.

Solar indices for 01 Nov 2021

Wolf number Catania	///
10cm solar flux	098
AK Chambon La Forêt	021
AK Wingst	009
Estimated Ap	009
Estimated international sunspot number	052 - Based on 22 stations

Noticeable events summary

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

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