Viewing archive of Friday, 8 September 2017

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2017 Sep 08 1245 UTC

SIDC Forecast

Solar flares

M-class flares expected (probability >=50%)

Geomagnetism

Minor storm expected (A>=30 or K=5)

Solar protons

Proton event in progress (>10 MeV)

	10cm flux	Ap
08 Sep 2017	130	054
09 Sep 2017	130	046
10 Sep 2017	125	024

Bulletin

Solar activity remained at high levels dominated by Catania sunspot group 46 (NOAA active region 2673) which produced another X1.3 flare peaking at 14:36 UT September 7. Later also 4 more M flares were produced by the region, the largest peaking at 07:48UT September 8, with magnitude M8.5. The region continues to contain strong mixed polarity field regions and exhibits a complex magnetic field configuration which warrants the expectation of further M flaring from this region, with also a significant chance for another X flare. This outlook is expected to persist over the next 2 days before the region starts turning around the Solar West limb. Coronagraph data indicate that ejecta associated with these flares are limited in angular extent and are not likely to influence Earth. Solar proton flux levels are for the >10MeV protons still above the event threshold of 10pfu, but values are decreasing. As Catania group 46 (NOAA active region 2673) remains to be active and is located favourably in terms of magnetic connection to Earth, possible renewed increases in proton fluxes must be anticipated over the next days.

At 22:29UT September 7, a shock was observed in the Solar wind, marking the arrival of the September 6 CME. Solar wind speed jumped to over 620 km/s and increased further afterwards to speeds between 700-800 km/s. Total magnetic field jumped to 23nT later reaching 34nT. Bz was strongly and persistently negative for the 3 hours following the shock with a peak down to -33nT. Total magnetic field was afterwards in the 14-20nT range with mostly no persistent periods of strongly negative Bz. However, since around 11:15UT Bz has been again strongly negative around -17nT. Elevated Solar wind conditions are expected to continue over the next 24h with a generally decreasing trend as the CME passes.

Geomagnetic conditions reached severe levels (NOAA Kp 8) for the two measurement periods around midnight with local conditions seeing only moderate geomagnetic storms (local K Dourbes 6). Further geomagnetic storming is expected over the next day due to the CME passage, but should not see severe magnitudes any more. In the next 48 hours a decay to unsettled to active conditions is expected.

Today's estimated international sunspot number (ISN): 098, based on 12 stations.

Solar indices for 07 Sep 2017

Wolf number Catania	123
10cm solar flux	129
AK Chambon La Forêt	069
AK Wingst	030
Estimated Ap	036
Estimated international sunspot number	108 - Based on 18 stations

Noticeable events summary

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

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