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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2021 May 18 1231 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
18 May 2021	075	007
19 May 2021	077	016
20 May 2021	079	007

Bulletin

Two active regions (ARs) visible on the disk, NOAA AR 2822 (inactive) and the AR rotating into view from the eastern limb. The latter produced a C1.1 flare at 02:09 UT. It was associated with an EUI wave and small eruption (that will not affect the Earth). More C-class flares can be expected, with a small chance of M-class flares.

No Earth-directed Coronal Mass Ejections (CMEs) have been detected in the available coronagraphic imagery in the last 24 hours.

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 remained below the 1000 pfu in the past 24 hours and is expected to remain so. The 24-hour electron fluence was at normal levels in the past 24 hours and is expected to remain so.

In the last 24 hours, the solar wind speed varied between 320 and 400 km/s. The interplanetary magnetic field polarity was mostly negative (towards the Sun). A weak shock was detected in DSCOVR data, the magnetic field jumped from 5 to 8 nT and the solar wind speed from 320 to 350 km/s, at 15:45 UT on 17 May. This could mark the arrival of the CME from May 13 (with the bulk of the ICME passing north of the Earth). After the shock, the interplanetary magnetic field reached 10 nT (with Bz up to -9 nT). The high speed solar wind from the coronal hole that crossed central meridian on 15 May is expected to arrive to the Earth in about 24 hours.

Geomagnetic conditions ranged from quiet to unsettled locally (KDourbes 0-3) and quiet to active (after the shock) at planetary levels (Kp 2-4). More active to minor storm conditions can be expected when the high speed solar wind stream arrives to the Earth in about 24 hours.

Today's estimated international sunspot number (ISN): 028, based on 25 stations.

Solar indices for 17 May 2021

Wolf number Catania	011
10cm solar flux	075
AK Chambon La Forêt	018
AK Wingst	008
Estimated Ap	008
Estimated international sunspot number	012 - Based on 29 stations

Noticeable events summary

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

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