Перегляд архіву четвер, 7 вересня 2017

Daily bulletin on solar and geomagnetic activity from the SIDC

Випущено: 2017 Sep 07 1230 UTC

SIDC Forecast

Сонячні спалахи

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

Geomagnetism

Moderate (ISES: Major) magstorm expected (A>=50 or K=6)

Сонячні протони

Proton event in progress (>10 MeV)

	10cm flux	Ap
07 Sep 2017	140	028
08 Sep 2017	140	062
09 Sep 2017	140	075

Bulletin

The reporting period was dominated by the strongest Solar flaring activity in many years. Catania group 46 (NOAA active region 2673) produced an X9.3 flare peaking at 12:02UT (the X9.3 magnitude was recorded by NOAA/GOES15 while it was recorded as X10 by NOAA/GOES13). This was the first X9 flare since 2006-12-05, and the most recent flare stronger than that of yesterday was the X17 flare of 2005-9-7 (exactly 12 years ago). Yesterdays event was associated with strong radio bursts over a wide range of the frequency spectrum, while EUV images show an on disk dimming and an EUV wave. All these phenomena are indicative of a CME initiation, that was later confirmed by SoHO/LASCO coronagraph images. The region afterwards produced some more M flares, the strongest of M7.3 magnitude peaking at 10:15UT this morning. 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 very significant chance for another X flare. This outlook is expected to persist over the next 3 days before the region starts turning around the Solar West limb.

Coronagraph images show the presence of an asymmetric but full halo CME associated to the X9.3 flare. The CME is first visible in SoHO/LASCO C2 images at 12:24UT in the South West. The measured projected speed based on SoHO/LASCO images is around 1100-1200 km/s. Also in STEREO-A/COR2 images the CME is visible as a full halo. Initial calculations estimate the arrival of the CME at Earth location around or after UT noon of September 8.

Following yesterdays activity the proton flux levels for >10MeV protons have again reached values over 100 pfu with maxima near 350 pfu. Values currently persist at above 100 pfu. Also higher energy protons were slightly elevated after the X9.3 flare with fluxes of 100MeV protons reaching around 0.6 pfu but meanwhile recovering to background values. 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.

Solar wind saw initially a steady decline in solar wind speed to 420km/s before at 23:08UT solar wind conditions became elevated due to the somewhat later than expected arrival of the September 4 CME. Solar wind speed jumped to just over 600km/s and total magnetic field jumped initially to 9nT, later increasing further to 16nT. Solar wind speed remained just below 600km/s since then, and up till now Bz only saw some brief periods of negative Bz with peaks down to -11nT. Solar wind conditions will remain elevated though slowly declining during the further passage of the September 4 CME before a renewed increase is expected tomorrow around or after UT noon due to the September 6 CME related to the X9.3 flare. As a result of the recent solar wind conditions, geomagnetic conditions have reached, but not exceeded, active levels (local K Dourbes and NOAA Kp 4). If longer periods of consistent negative Bz occur this could cause some geomagnetic storming over the next 24 hours but given the solar wind speed at around 500 km/s presently, this is expected to reach not above minor storm levels. Further geomagnetic storming at minor to moderate level must be anticipated over the next 48-72 hours due to the arrival of the September 6 CME.

Today's estimated international sunspot number (ISN): 105, based on 14 stations.

Solar indices for 06 Sep 2017

Wolf number Catania	142
10cm solar flux	133
AK Chambon La Forêt	017
AK Wingst	012
Estimated Ap	011
Estimated international sunspot number	114 - Based on 21 stations

Noticeable events summary

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

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