Solar Terrestrial Activity ReportSolar Terrestrial Activity Report

Last update September 28, 2001 at 06:30 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 1, 2001)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 1, 2001)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update September 1, 
2001)]
[Historical solar and geomagnetic data charts 1954-2001 (last update July 27, 
2001)]
Recent development
The geomagnetic field was quiet tounsettled on September 27. Solar wind speed 
ranged between 403 and 584 km/sec. A new and fairly weak disturbance began 
around noon and solar wind speed increased slowly towards midnight. This may 
have been a coronal stream or the effects of a CME associated with a major flare 
in region 9628 on September 25.
Solar flare activity was moderate. Solar flux was 269.5, the planetary A index 
was 10 (3-hour K indices: 1113 3333, Boulder K indices: 2123 3333). Regions 9620 
and 9621 were quiet and stable, both regions are about to rotate off the visible 
disk. Region 9624 was quiet and stable. Region 9627 decayed further and was 
spotless by early afternoon. Region 9628 decayed further. A major flare is still 
possible. Region 9632 did not change much and remains capable of producing major 
M or X class flares. Region 9633 was quiet and stable, as were regions 9634 and 
9635. Region 9636 decayed slowly and was quiet. Region 9637 was quiet and 
stable. Region 9638 decayed and could become spotless today. Region 9639 was 
quiet and stable. New region 9640 rotated into view at the northeast limb and 
appears to be decaying. New region 9641 rotated into view at the southeast limb.
Flares and CMEs
A total of 1 C and 1 M class events were observed on September 27. Region 9628 
produced a C3.8 flare at 04:32 UTC. This region was also the source of a very 
long duration M1.0 event which peaked at 12:13 UTC and was associated with a 
large and wide partial halo coronal mass ejection where most of the ejection was 
observed over the southwest limb. The CME could have geoeffective extensions.
The background x-ray flux is at the class C2 level.
Coronal holes
A weak coronal hole is located east of region 9635 and was in a geoeffective 
position on September 26. Any effects from this coronal hole on the geomagnetic 
field are uncertain. The associated coronal stream could arrive on September 29.
Forecast
The geomagnetic field is expected to be quiet to unsettled on September 28 and 
quiet to active on September 29. Long distance medium wave (AM) band propagation 
along east-west paths over high and upper middle latitudes is very poor to 
useless.
      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
      96202001.09.161N12W770040HSX 
      96212001.09.161N14W720110HAX 
      96232001.09.17 N21W87  plage
      96242001.09.171N03W670090HSX 
      96262001.09.18 N25W79  plage
      96272001.09.182N00W490000AXX 
      96282001.09.1837S18W370780EKCgamma-delta
      96292001.09.19 N26W68  plage
      96322001.09.2017S19W210710DKCbeta-gamma-delta
      96332001.09.221N22E100070HSX 
      96342001.09.228N12E110110DAO 
      96352001.09.2310N21W380060DSO 
      96362001.09.2428N13E260370FAIbeta-gamma
      96372001.09.2410S14E320200DAO 
      96382001.09.251N03E350000AXX 
      96392001.09.267N04E210030DSO 
      96402001.09.274N10E670040CSO 
      96412001.09.271S14E770060HSX 
      Total number of sunspots:129 

Monthly solar data
      MonthAverage solar fluxInternational sunspot numberSmoothed sunspot number
      2000.03208.2138.5119.9
      2000.04184.2125.5120.8
      cycle 23 sunspot max. 
      2000.07202.3170.1119.7
      2000.08163.0130.5118.6 (-1.1)
      2000.09182.1109.7116.3 (-2.3)
      2000.10167.499.4114.5 (-1.8)
      2000.11178.8106.8112.8 (-1.7)
      2000.12173.6104.4112.1 (-0.7)
      2001.01166.695.6108.8 (-3.3)
      2001.02146.680.6104.1 (-4.7)
      2001.03177.7113.5(105.7 predicted, +1.6)
      2001.04177.7108.2(108.8 predicted, +3.1)
      2001.05147.197.3(108.0 predicted, -0.5)
      2001.06173.0134.0(106.3 predicted, -1.7)
      2001.07131.382.2(105.0 predicted, -1.3)
      2001.08162.9106.8(105.6 predicted, +0.6)
      2001.09231.7 (1)205.9 (2)(105.0 predicted, -0.6)

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 25-40% 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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