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# SIDC Weekly bulletin on Solar and Geomagnetic activity #
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WEEK 543 from 2011 May 23
SOLAR ACTIVITY
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Solar activity was rather low in the beginning of the week, with the background solar X-ray level marginally at B-level. Two C-class flares occurred late on May 25: the first one (peaking at 21h03) was a C1.1 flare, the second one a C1.4 flare peaking at 21h58. Both originated from a fast emerging region that was later numbered as Cat 93 (NOAA 1223). The flaring activity picked up significantly on May 27th when NOAA AR 1226 (Cat 98) started to turn over the east limb of the Sun. This region now has a beta-delta magnetic configuration and produced numerous C- flares starting on May 27th and in the days after that. It released an M1.1 flare peaking at 21h50 on May 28th, as well as an M1.4 flare on May 29th, with a maximum around 10h33.
Apart from eruptions on the far side of the Sun, the STEREO and SOHO spacecraft detected the following events. A small and narrow CME was seen by COR2 on the morning of May 23rd at 3h39, originating from an unnumbered region in the north. As it was directed northwards, the CME did not influence the earth. An earth-directed CME was observed by COR2 on May 25th starting around 13h09, probably linked to a filament eruption in the NE quadrant. Other CME's towards the earth occurred on May 27th around 18h24 (possibly linked to the C5.6 flare from AR 1226) and on May 29th. This last one was associated with the M1.4 flare on that day (11h24), occurred in the SE and is not expected to be geo-effective. A high speed eastward CME was seen on May 29th around 21h24 in association with a C8.7 flare in region NOAA 1227 (Cat 99) and a type II radio burst.
GEOMAGNETIC ACTIVITY
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Geomagnetic conditions were quiet during the biggest part of the week. From May 27th to May 29th, we experienced active conditions with local K index (Dourbes) up to K=5 (Kp up to 6) during several 3h periods. This geomagnetic activity was a combination of the arrival of a high speed wind stream from a recurrent coronal hole and the ICME from the eruption on May 25th (arriving on May 28th around 7h). The solar wind speed increased up to 800 km/s, while the southward component of the magnetic field went down to -12 nT.
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DAILY INDICES
DATE RC EISN 10CM Ak BKG M X
2011 May 23 /// 022 84 005 A9.1 0 0
2011 May 24 /// 008 82 010 A7.4 0 0
2011 May 25 035 016 80 004 A7.3 0 0
2011 May 26 053 031 83 008 A7.2 0 0
2011 May 27 074 042 90 014 B2.2 0 0
2011 May 28 /// 050 101 038 B5.5 1 0
2011 May 29 /// 069 111 033 B5.3 1 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
28 2109 2150 2201 S20E71 M1.1 SF 1226
29 1008 1033 1108 S22E65 M1.4 1F II/1 98 1226 associated CME ~ 550 km/s
#--------------------------------------------------------------------#
# Solar Influences Data analysis Center - RWC Belgium #
# Royal Observatory of Belgium #
# Fax : 32 (0) 2 373 0 224 #
# Tel.: 32 (0) 2 373 0 491 #
#--------------------------------------------------------------------#
# SIDC Weekly bulletin on Solar and Geomagnetic activity #
#--------------------------------------------------------------------#
WEEK 543 from 2011 May 23
SOLAR ACTIVITY
--------------
Solar activity was rather low in the beginning of the week, with the background solar X-ray level marginally at B-level. Two C-class flares occurred late on May 25: the first one (peaking at 21h03) was a C1.1 flare, the second one a C1.4 flare peaking at 21h58. Both originated from a fast emerging region that was later numbered as Cat 93 (NOAA 1223). The flaring activity picked up significantly on May 27th when NOAA AR 1226 (Cat 98) started to turn over the east limb of the Sun. This region now has a beta-delta magnetic configuration and produced numerous C- flares starting on May 27th and in the days after that. It released an M1.1 flare peaking at 21h50 on May 28th, as well as an M1.4 flare on May 29th, with a maximum around 10h33.
Apart from eruptions on the far side of the Sun, the STEREO and SOHO spacecraft detected the following events. A small and narrow CME was seen by COR2 on the morning of May 23rd at 3h39, originating from an unnumbered region in the north. As it was directed northwards, the CME did not influence the earth. An earth-directed CME was observed by COR2 on May 25th starting around 13h09, probably linked to a filament eruption in the NE quadrant. Other CME's towards the earth occurred on May 27th around 18h24 (possibly linked to the C5.6 flare from AR 1226) and on May 29th. This last one was associated with the M1.4 flare on that day (11h24), occurred in the SE and is not expected to be geo-effective. A high speed eastward CME was seen on May 29th around 21h24 in association with a C8.7 flare in region NOAA 1227 (Cat 99) and a type II radio burst.
GEOMAGNETIC ACTIVITY
--------------------
Geomagnetic conditions were quiet during the biggest part of the week. From May 27th to May 29th, we experienced active conditions with local K index (Dourbes) up to K=5 (Kp up to 6) during several 3h periods. This geomagnetic activity was a combination of the arrival of a high speed wind stream from a recurrent coronal hole and the ICME from the eruption on May 25th (arriving on May 28th around 7h). The solar wind speed increased up to 800 km/s, while the southward component of the magnetic field went down to -12 nT.
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DAILY INDICES
DATE RC EISN 10CM Ak BKG M X
2011 May 23 /// 022 84 005 A9.1 0 0
2011 May 24 /// 008 82 010 A7.4 0 0
2011 May 25 035 016 80 004 A7.3 0 0
2011 May 26 053 031 83 008 A7.2 0 0
2011 May 27 074 042 90 014 B2.2 0 0
2011 May 28 /// 050 101 038 B5.5 1 0
2011 May 29 /// 069 111 033 B5.3 1 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
28 2109 2150 2201 S20E71 M1.1 SF 1226
29 1008 1033 1108 S22E65 M1.4 1F II/1 98 1226 associated CME ~ 550 km/s
#--------------------------------------------------------------------#
# Solar Influences Data analysis Center - RWC Belgium #
# Royal Observatory of Belgium #
# Fax : 32 (0) 2 373 0 224 #
# Tel.: 32 (0) 2 373 0 491 #
#--------------------------------------------------------------------#