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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2017 Sep 13 1230 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

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

Protoni solari

Proton event in progress (>10 MeV)

	10cm flux	Ap
13 Sep 2017	077	023
14 Sep 2017	076	015
15 Sep 2017	075	008

Bulletin

Strongest flare observed in the last 24 hours was the C1.6 flare (peaked at 19:20 UT on September 12), which originated from the Catania sunspot group 55 (NOAA AR 2680). The flare was, similarly to the C-class flare from this active region reported yesterday, associated with the EIT wave, coronal dimming, and rather slow and narrow CME (with projected speed of 350 km/s and angular width of about 100 degree). This CME will not arrive at the Earth. We might expect more isolated C-class flares in the coming hours (probability is about 25%), in particular from the Catania sunspot group 55 (NOAA AR 2680). The particle event, associated with the X8.2 flare is still on going, but the level of the proton fluxes is decreasing, and presently only fluxes with >10 MeV are slightly above the event threshold.

The sudden jump of the solar wind speed (up to maximum value of 650 km/s) and simultaneous increase of the density and interplanetary magnetic field magnitude (up to 16 nT) observed at about 19:26 UT on September 12 indicated arrival of the decayed CME-driven shock wave associated with the X8.2 flare observed on September 10. The shock was followed by the post- shock sheath region. The solar wind speed decreased rather fast and it is presently about 460 km/s.The interplanetary magnetic field magnitude is about 5 nT. The longer intervals of the southward Bz component and fast solar wind induced minor geomagnetic storm conditions starting at about 21:00 UT on September 12 and lasting until about 03 UT on September 13 (local station at Dourbes reported K=5 and NOAA reported Kp=5). The fast solar wind, associated with the low latitude coronal hole in the northern hemisphere which reached the central meridian on September 10, is expected to arrive at the Earth today. We expect quiet to active conditions within next 24 hours due to arrival of the fast solar wind.

Today's estimated international sunspot number (ISN): 018, based on 19 stations.

Solar indices for 12 Sep 2017

Wolf number Catania	012
10cm solar flux	076
AK Chambon La Forêt	031
AK Wingst	019
Estimated Ap	021
Estimated international sunspot number	012 - Based on 30 stations

Noticeable events summary

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

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