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RWC Belgium World Data Center for the Sunspot Index

Solar Influences Data analysis Center (SIDC)

Since 1981, the Royal Observatory of Belgium harbours the Sunspot Index Data center, the World data center for the Sunspot Index. SIDC analyses solar activity and provides services on three different time scales: 1. Fast warnings and real time monitoring; 2. Forecasts and middle term analysis; 3. Post-event analysis and long term solar cycle analysis.

Royal Observatory of Belgium
Av. Circulaire, 3 - Ringlaan 3
1180 BRUXELLES - BRUSSEL

World Data Center System

CODES, TERMINOLOGY AND CLASSIFICATIONS

The impact on Earth of solar activity have been observed roughly since World War II, when the Sun was recognised as an important source of radio noise affecting military radars, and when it appeared that radio-communications were sometimes highly perturbed as a consequence of big solar flares. Today, the scientific, technical, human and economical impacts of the Solar-Terrestrial relations are widely recognised (Koshinen et al, 1999). The sunspot number is the oldest solar index measuring the solar activity and its main interest results from its long-term behaviour and the length of its series. For a long time, it was the only index representative of the solar cycle, and many studies on the cyclical behaviour of the Sun were led using the Sunspot Number. That is the reason why the international scientific community, through the International Council of Scientific Unions (ICSU), has renewed many times the expression of its high interest in this index and committed its computation to a specific service like the SIDC.

The SIDC was founded in 1981 to continue the work of the Zurich Observatory, when this institution decided to stop publishing the sunspot number. An agreement was therefore taken between the ETHZ at Zurich (represented by O. Stenflo), the Specola Solare Ticinese at Locarno (represented by S. Cortesi) and the SIDC (represented by A. Koeckelenbergh). Following this agreement, the Sunspot Index Data center, started in January 1981 with the production of a sunspot index, called International Sunspot Number. The continuity and coherence with the former index of Zurich was assured through the use of Locarno (one of the three main stations of the Zurich network) as reference station. The SIDC now also provides daily activity reports and forecasts of the status of the space environment. This 'space weather' activity is part of the International Space Environment Services (ISES) that co-ordinates 10 regional warning centers (RWC). These 10 warning centers exchange mutually the latest space weather related data and make it available to a wide public. The SIDC is part of the Department of Solar Physics of the Royal Observatory of Belgium (ROB) and has available the complete archive of the EIT (Extreme UV Imaging Telescope on board SOHO) observations, and the know-how acquired by the local team of co-investigators in the EIT experiment. The archive covers now the whole rising part of cycle 23, and allows long-term analysis of the data.

SIDC weekly bulletin - (WEEK 211 from 2005 Jan 10 )

SOLAR ACTIVITY

The first part of the week was quiet. There was a small coronal hole in the southern solar hemisphere (which was near the central meridian on Jan 07) which pushed the solar wind speed up to values around 700 km/s on Jan 12. A second northern coronal hole at high latitude was located at the central meridian on Jan 10. This coronal hole can possible be the cause of a second, smaller bulb in the solar wind speed measured by ACE on Jan 15. A part from this coronal hole, two sunspot groups 03 and 04, (NOAA 718 and 719) were responsible for the C-flaring activity. Sunspot group 05 (NOAA 720) came in view from Jan 10 onwards, grew very fast in size and complexity, although it was until Jan 13 responsible for only a few B-flares.

>From Jan 14 onwards, 05 (0720) marked a new period. Up till Jan 16, it was responsible for 9 M-flares and 2 X-flares, 03 (0718) has put its name on 2 M-flares.

We pay attention to two flares since they were accompanied by a full halo CME and increased proton fluxes. The first violent outburst was an M8.6 flare peaking at 06:38, Jan 15. CACTus detected a full halo CME coming out of the occulting disk at 06:06, with a median/maximum speed of 889/1745 km/s. The second flare accompanied by a full halo CME was an X2.6 peaking 23:02UT Jan 15. This time the CME was detected to come in field of view at 23:06UT and had a median/maximum speed of 1488/1960 km/s. Both CMEs are formally associated with those flares because only with those flares a type II outburst was seen. It is possible that a CME leaves the Sun before an associated flare reaches its peak. The proton fluxes increased around 07:30UT on Jan 15, but did not pass the threshold. Just after midnight, a second time the fluxes were pushed upwards. The >10MeV curve passed the threshold a little later, the >50MeV passed the threshold slightly around 15:00UT on Jan 16. The curves show both a flare and CME-shockfront driven increase. To be updated, on Jan 17, a third X-flare happened: X3.8, also accompanied by a full halo CME and a big proton event (all three curves increased drastically). Because of the proton event, the ACE SWEPAM instrument is contaminated.

GEOMAGNETIC ACTIVITY

>From Jan 11 up till Jan 12, Boulder (NOAA) calculated active to minor storm conditions, caused by the small southern coronal hole mentioned above. On Jan 15, we had another period with K_p ranging from 4 up till 6, this time caused by the northern coronal hole.

On Jan 16, ACE data showed a changing in several physical quantities(around 10:30UT): higher density, decreasing temperature, high solar wind speed, increased total interplanetary magnetic field. These are signatures of an ICME passing ACE: possibly the arrival of the first full halo CME. A minor storm just after midnight in the night between Jan 16 and Jan 17 was the consequence. A clear shock was be seen in ACE-data on Jan 17 at 7:00UT. Possibly the arrival of the second full halo CME associated with the X2.6-flare peaking at 23:02UT on Jan 15. A severe storm (K_p= 7) was the consequence. At the time of writing this bulletin (Jan 18), we are in the declining phase of this storm and waiting for the third full halo CME to arrive at earth which possibly initiates another severe storm.

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DAILY INDICES
DATE           RC   10CM   Ak   BKG    M   X
2005 Jan 10   040   90    ///   A7.9   0   0
2005 Jan 11   047   94    ///   A8.6   0   0
2005 Jan 12   083   102   ///   B1.6   0   0
2005 Jan 13   069   116   ///   B2.6   0   0
2005 Jan 14   092   130   ///   B7.3   4   0
2005 Jan 15   ///   145   ///   C1.6   6   2
2005 Jan 16   094   145   ///   C1.6   1   0
# RC  : Sunspot index from Catania Observatory (Italy)
# 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)
---------------------------------------------------------------------------------
NOTICEABLE EVENTS
DAY BEGIN MAX  END  LOC    XRAY OP TENCM TYPE        Cat NOAA NOTE 
14  1353  1411 1445 N13E14 M1.8 SF                   05  0720 
14  1602  1606 1614        M1.0    67    V/2         03  0718 
14  1753  1757 1803        M1.5                      05  0720 
14  2108  2126 2139 N15E08 M1.9 2N                   05  0720 
15  0022  0043 0102 N11E10 X1.2 1B 97                05  0720 
15  0409  0416 0422 N11E08 M1.3 2N       III/2       05  0720 
15  0426  0431 0436 N14E06 M8.4 2N                   05  0720 
15  0554  0638 0717 N11E06 M8.6 SF 3000  IV/2,II/2   05  0720 fast full halo CME
15  1141  1148 1150 N12E04 M1.2 SF                   05  0720 
15  1408  1423 1439 S08W11 M3.2 SF 420   III/3       03  0718 
15  2201  2208 2216 N14W09 M1.0 SF                   05  0720 
15  2225  2302 2331 N14W08 X2.6 3B 6400  II/2        05  0720 full halo CME
16  2155  2203 2222 N13W16 M2.4 1N 54    III/3       05  0720 
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