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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2017 Sep 24 1230 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
24 Sep 2017	084	009
25 Sep 2017	087	016
26 Sep 2017	090	007

Bulletin

Over the past 24 hours the solar activity was very low. Only small B-class flares and one non-Earth directed slow-speed CME were recorded. Catania sunspot groups 56 (NOAA active regions 2681) has increased its magnetic complexity (from Alpha to Beta class), but has not shown any flaring activity. The returning region NOAA active region 2682 (previously, Catania sunspot group 46, NOAA active region 2673) is now on the visible disc and is the source of the slow-speed CME and B-class flaring activity. Its magnetic complexity is difficult to estimate due to the projection effect, however, it seems to have drastically decay from the previous solar rotation. We expect the solar activity to increase due to the return of this region with C-class flares.

No Earth directed CMEs have been observed and the solar protons remained at background level over the past 24 hours. The Earth remained inside a slow solar wind flow. The speed has further decreased from about 400 to 330 Km/s. The interplanetary magnetic field magnitude remained below 6 nT and the Bz component fluctuated between -5 and 5 nT. The associated fast solar wind to the small equatorial coronal hole that has crossed the central meridian on Sept 20 has not arrived yet and is expected to arrive at Earth today. A new larger coronal hole with positive polarity is currently facing Earth. This coronal hole is elongated from the north solar pole to the solar Equator and its high speed stream is expected to arrive at Earth in about 3 days from now (on Sept 27).

Geomagnetic conditions were quiet with Kp (NOAA) and local K (Dourbes) indexes ranging between 1-2. The geomagnetic conditions are expected to become more active with the arrival of the high speed stream from the coronal hole that has crossed the central meridian on Sept 20. As this coronal hole was relatively small, no strong or sever magnetic storm is expected.

Today's estimated international sunspot number (ISN): 023, based on 18 stations.

Solar indices for 23 Sep 2017

Wolf number Catania	///
10cm solar flux	081
AK Chambon La Forêt	009
AK Wingst	007
Estimated Ap	005
Estimated international sunspot number	013 - Based on 27 stations

Noticeable events summary

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

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