Solar Terrestrial Activity Report

Last update September 12, 2002 at 04:15 UTC.
[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 3, 2002)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 3, 2002)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update September 3, 
2002)]
[Historical solar and geomagnetic data charts 1954-2002 (last update August 16, 
2002)]
Recent development
The geomagnetic field was quiet to major storm on September 11. Solar wind speed 
ranged between 397 and 540 km/sec. The disturbance which began late on September 
9 continued until about 09h UTC on Sept.11 when a coronal stream began to 
dominate the solar wind.
Solar flare activity was moderate. Solar flux was 216.1, the planetary A index 
was 28 (3-hour planetary K indices: 2356 4444, Boulder K indices: 2145 3534). 
Region 10100 decayed slowly and quietly and had only a single small spot left by 
the end of the day. The region could become spotless today. Region 10101 decayed 
and was spotless by late afternoon. Region 10103 decayed significantly losing a 
large amount of penumbral area in the trailing spots section. The region is 
simply structured with no evidence of polarities intermixing. Region 10105 lost 
some penumbral area in the spots ahead of the largest penumbra. Several small 
spots emerged around the dominant penumbra. There is no longer a magnetic delta 
in the leading spots. The trailing spot section (actually another independent 
region, neither the positive nor the negative polarity area is shared with that 
of the leading section of spots) still has a magnetic delta structure and is a 
possible site for M class flares. Region 10107 added some penumbral area but was 
otherwise mostly unchanged. Region 10108 decayed and could become spotless 
today. Region 10109 developed slowly and quietly. Region 10110 developed early 
in the day, then began to decay slowly,
Flares and CMEs
A total of 7 C and 1 M class events was recorded on September 11. Region 10107 
produced a C2.1 flare at 07:35, a C1.5 flare at 05:54, a C1.3 flare at 15:03 and 
a C1.2 flare at 23:00 UTC. Region 10105 generated an M2.2/2B flare at 07:35 UTC.
The background x-ray flux is at the class B6 level.
Coronal holes
No obvious coronal holes are currently rotating into geoeffective positions.
Forecast
The geomagnetic field is expected to be quiet to active on September 12 and 
quiet to un settled on September 13-14. Long distance medium wave (AM) band 
propagation along east-west paths over high and upper middle latitudes is very 
poor.
Coronal holes (1)Coronal mass ejections (2)M and X class flares (3)
    
    
    1) Effects from a coronal hole could reach Earth within the next 5 days.
2) Material from a CME is likely to impact Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 
hours.
Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.
Active solar regions (Recent map)
Solar regionDate numberedActual no. sunspotsLocation at 
            midnightAreaClassificationComment
    100962002.08.30 S14W83  plage
    100982002.08.31 S10W67  plage
    101002002.09.012S19W640030HRXarea near 0010 at
            midnight
    101012002.09.013N02W630010BXOnow spotless
    101022002.09.02 N08W52  plage
    101032002.09.0335N15W330490EKC strange attempt at
            classification by
            SEC/NOAA, EAI
            would have been more
            precise. Area near
            0350 at midnight.
    101042002.09.07 N10E02  plage
    101052002.09.0756S09E281370FKIbeta-gamma-delta
            actually two separate
            regions
    101062002.09.08 N27E10  plage
    101072002.09.0815N11E300170DAO 
    101082002.09.102S24E360010BXO
    101092002.09.1011S08E050060DSO
    101102002.09.109N20E050100DAO
    Total number of sunspots:133
    
    Monthly solar data
MonthAverage solar fluxInternational sunspot numberSmoothed sunspot 
            number
    2000.04184.2125.5120.8
            cycle 23 sunspot max. 
    2000.07202.3170.1119.8
    2001.08162.9106.4113.6 (+1.8)
    2001.09233.2 150.7114.1 (+0.5)
    2001.10207.6125.5114.0 (-0.1)
    2001.11210.6106.5115.5 (+1.5)
    2001.12235.1132.2114.6 (-0.9)
    2002.01226.6114.1113.5 (-1.1)
    2002.02205.0107.4114.7 (+1.2)
    2002.03179.598.4(113.2 predicted, -1.5)
    2002.04189.8120.4(108.7 predicted, -4.5)
    2002.05178.4120.8(104.2 predicted, -4.5)
    2002.06148.788.5(99.7 predicted, -4.5)
    2002.07173.599.9(94.9 predicted, -4.8)
    2002.08183.6116.4(90.8 predicted, -4.1)
    2002.09187.8 (1)78.1 (2)(87.1 predicted, -3.7)
    
    1) Running average based on the daily 20:00 UT solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (SEC/NOAA) sunspot number. 
The official international sunspot number is typically 25-45% less.
This report has been prepared by Jan Alvestad. It is based partly on my own 
observations and interpretations, and partly on data from sources noted in solar 
links. Comments and suggestions are always welcome.


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