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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2018 Aug 20 1245 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
20 Aug 2018	067	023
21 Aug 2018	067	029
22 Aug 2018	067	017

Bulletin

Solar activity was very quiet with X-ray flux remaining below B level. NOAA active region 2718 has decayed while the newly developing small bipolar region in the East was numbered NOAA 2719. X-ray flux is expected to remain below C level.

Around 5:00UT August 19, a minor but long duration A-flare from region 2718 was associated with an on disk dimming (5:40UT august 19), evidencing an eruptive phenomenon. In SoHO/LASCO C2 coronagraph images a very narrow (only around 10 degrees angular width) CME is visible from August 19 7:36UT onwards, directed towards the South-West. It is also visible from Stereo A COR2, also narrow and directed to the South-West from this viewpoint. From the Stereo COR2 images a radial speed of around 1000 km/s may be estimated. Given the narrow angular extent and the direction of the ejecta (no halo character from Earth perspective), the bulk of this CME is expected to go South of the Earth.

Proton flux levels were at background values and are expected to remain so.

Solar wind conditions were indicative of the arrival of the expected high speed stream from the transequatorial negative polarity coronal hole. Solar wind speed reached a minimum of close to 400 km/s near the start of the period and then started a steady increase to current values of over 650 km/s. Between 17UT and 8UT total magnetic field was enhanced reaching values of close to 14nT, but the Bz component was mainly positive. Meanwhile, total magnetic field has restored to below 5nT. Solar wind speed is still expected to increase and is expected to remain elevated for several days given the extent of the coronal hole. For the CME of August 19 the bulk of the CME is expected to go South of the Earth but there remains a possibility that a shock arrives at Earth. If this occurs this is expected around midnight August 21/22 but its effect will be small within the already elevated background solar wind conditions. Geomagnetic conditions were mainly quiet to unsettled (K Dourbes and NOAA Kp 1-3) with an isolated active period for Kp around midnight. Geomagnetic conditions may reach active levels under the influence of the high speed stream over the next days.

Today's estimated international sunspot number (ISN): 016, based on 15 stations.

Solar indices for 19 Aug 2018

Wolf number Catania	///
10cm solar flux	067
AK Chambon La Forêt	018
AK Wingst	011
Estimated Ap	010
Estimated international sunspot number	018 - Based on 27 stations

Noticeable events summary

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

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