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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2021 Apr 30 1243 UTC

SIDC Forecast

Brillamenti solari

Quiet conditions (<50% probability of C-class flares)

Geomagnetism

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

Protoni solari

Quiet

	10cm flux	Ap
30 Apr 2021	076	012
01 May 2021	076	031
02 May 2021	075	031

Bulletin

X-ray flux has remained below C level throughout the period. Several B-class flares originated from the complex of the Catania groups 91 and 92 (NOAA regions 2821 and 2820) which all in all is in decay while approaching the West limb. X-ray flux is likely to remain below C level though an isolated C-flare is still possible.

An Eastbound CME can be detected in SoHO/LASCO C2 coronagraph images from 20:01UT onwards (after a datagap), associated to activity in the North- Eastern quadrant. It is not likely to be geoeffective, but remains to be analysed in more detail.

The greater than 10 MeV proton flux was at nominal levels over the past 24 hours and is expected to remain so for the next 24 hours. The greater than 2 MeV electron flux just touched the 1000 pfu event threshold. The 24h electron fluence was at normal levels. Electron fluence is expected to remain at normal levels during next days.

Solar wind parameters showed a weak fast forward shock as measured by DSCOVR data at 18:44UT. Speed jumped from 329 to 349 km/s and magnetic field from 5.9 to 8.5nT. Also weak jumps in density and temperature were associated. Since then magnetic field has remained slightly elevated (6-10nT) while Solar wind speed has declined again to around 300 km/s. The magnetic field phi angle slowly shifted before the shock arrival from the negative to the positive sector and remained in the positive sector since. We may be seeing an earlier than expected arrival of the April 25 CME, but it does not seem to carry very significant magnetic field strengths. We are expected to see from tomorrow an increase in the Solar wind speed associated with the positive polarity coronal hole that transited the central meridian in the past days. In addition to that we may see magnetic field perturbations due to a passing magnetic cloud from the April 26 CME, though likelihood and confidence for that arrival is low.

As Solar wind speed is low and magnetic field did not reach very high values nor did the Bz component turn significantly negative, geomagnetic conditions were essentially quiet (NOAA Kp 0-2) while local K Dourbes registered an isolated unsettled period. Geomagnetic conditions are expected to be quiet to active over the next days associated to the expected Solar wind perturbations, with also a slight chance for minor storm levels being reached.

Today's estimated international sunspot number (ISN): 031, based on 22 stations.

Solar indices for 29 Apr 2021

Wolf number Catania	042
10cm solar flux	077
AK Chambon La Forêt	008
AK Wingst	005
Estimated Ap	004
Estimated international sunspot number	036 - Based on 21 stations

Noticeable events summary

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

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