martedì 15 novembre 2011

SIDC Weekly Bulletin

:Issued: 2011 Nov 14 2110 UTC
:Product: documentation at http://www.sidc.be/products/bul
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# SIDC Weekly bulletin on Solar and Geomagnetic activity            #
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WEEK 567 from 2011 Nov 07 

SOLAR ACTIVITY
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Seventeen sunspot groups were detected during the week: Catania numbers 27 (NOAA AR 1334), 29 (NOAA AR 1337), 30 (NOAA AR 1338), 31 (NOAA AR 1339), 32 (NOAA AR 1344), 33 (NOAA AR 1340), 34 and 41 (together constituting NOAA AR 1342), 35 and 37 (together constituting NOAA AR 1341), 36 (NOAA AR 1343), 38 and 39 (together constituting NOAA AR 1344), 40 (NOAA AR 1345), 42 (unreported by NOAA), and NOAA ARs 1346 (not reported by Catania during the week; Catania numbers 46 and 47 on November 14) and 1347 (not reported by Catania during the week; Catania number 45 on November 14). Flaring activity at the C-class level was produced by Catania sunspot groups 31, 35, 38, and 45 (NOAA ARs 1339, 1341, 1344, and 1347, respectively).

The strongest flare observed during the week was the M1.1 flare peaking at 13:35 UT in Catania sunspot group 34 (NOAA AR 1342) on November 9. It was accompanied by a type II radio burst observed by Humain. PROBA2/SWAP and SDO/AIA detected associated filament eruption and coronal dimmings indicating the eruption of a CME. A full halo CME was detected by SOHO/LASCO first visible in the LASCO C2 field of view at 13:36 UT. Its speed was around 1000 km/s. The CME-driven shock arrived at the Earth on November 12 (see below).

Another partial halo CME was first visible in the LASCO C2 field of view at 11:36 UT on November 8. It had the angular width of around 120 degrees and speed around 500 km/s. The CME source region was situated at the west limb (Catania number 27, NOAA AR 1334). The data taken by SECCHI/COR2 onboard STEREO A confirmed that a part of this CME was directed towards the Earth. This CME was most probably the driver of the shock detected by ACE on November 11 (see below).

The C4.2 flare peaking at 07:05 UT on November 11 in the Catania sunspot group 38 (NOAA AR 1344) was also associated with a weak partial halo CME first seen in the LASCO C2 field of view at 07:12 UT. Due to the weakness of the halo and its moderate speed (around 700 km/s), no interplanetary counterpart was detected by ACE or SOHO/CELIAS at the moment of writing.

An active region right behind the north-east limb (one of returning NOAA ARs 1330 or 1333) produced a strong limb partial halo CME on November 12 (first appearance in the LASCO C2 field of view 18:36 UT, angular width 200 degrees, speed around 650 km/s). Due to the behind the limb position of its source region, the CME is not expected to be geoeffective.

GEOMAGNETIC ACTIVITY
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In the beginning of the week the Earth was situated inside a slow solar wind flow. Geomagnetic conditions were quiet. A weak shock was detected by ACE around 03:00 UT on November 11. It was most probably associated with the partial halo CME on November 8 (see above). As the solar wind speed stayed low (around 430 km/s) and the interplanetary magnetic field (IMF) magnitude reached only moderate values (around 8 nT), no geomagnetic disturbance followed.

Another interplanetary shock was detected by ACE and SOHO/CELIAS around 05:18 UT on November 12. The shock was most probably driven by the ICME corresponding to the halo CME observed on the Sun on November 9. Again, due to moderate values of the solar wind speed (up to 460 km/s) and the IMF magnitude (up to 9 nT), the geomagnetic conditions remained quiet.

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DAILY INDICES
DATE          RC  EISN  10CM  Ak  BKG    M  X
2011 Nov 07  227    119  182  005  B7.6  0  0
2011 Nov 08  ///    118  181  006  B6.7  0  0
2011 Nov 09  ///    118  180  001  B6.5  1  0
2011 Nov 10  233    119  179  004  B6.9  0  0
2011 Nov 11  184    107  174  003  B7.7  0  0
2011 Nov 12  ///    104  169  003  B7.2  0  0
2011 Nov 13  ///    109  155  002  B6.8  0  0
# RC  : Sunspot index (Wolf Number) from Catania Observatory (Italy)
# EISN : Estimated International Sunspot Number
# 10cm : 10.7 cm  radioflux (DRAO, Canada)
# Ak  : Ak Index Wingst (Germany)
# BKG  : Background GOES X-ray level (NOAA, USA)
# M,X  : Number of X-ray flares in M and X class, see below (NOAA, USA)
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NOTICEABLE EVENTS
DAY BEGIN MAX  END  LOC    XRAY OP TENCM TYPE                      Cat NOAA NOTE
09  1304  1335 1412 N24E35 M1.1          II/2,III/2                34  1342 SolarSoft location


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