Solar Terrestrial Activity ReportSolar Terrestrial Activity Report

Last update September 27, 2001 at 06:00 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 to minor storm on September 26. Solar wind speed 
ranged between 446 and 682 km/sec, gradually decreasing throughout the day.
Solar flare activity was moderate. Solar flux was 282.6 (new high for solar 
cycle 23), the planetary A index was 24 (3-hour K indices: 5454 3322, Boulder K 
indices: 5354 2222). Regions 9620 and 9621 were quiet and stable. Region 9622 
decayed further as it rotated off the visible disk. Region 9624 was quiet and 
stable. Region 9627 decayed quickly and could become spotless later today. 
Region 9628 decayed slightly but is still complex and capable of major flare 
production. Region 9632 did not change much and remains capable of producing 
major M or X class flares. Region 9633 was quiet and stable, as was region 9634. 
Region 9635 decayed slowly and quietly. Region 9636 developed slowly and has a 
weak magnetic delta to the northwest of the main penumbra. Minor M class flares 
are possible. Region 9637 was quiet and stable, as was region 9638. New region 
9639 emerged in the northeast quadrant ahead of region 9638. A new region is 
rotating into view at the northeast limb.
Flares and CMEs
A total of 3 C and 1 M class events were observed on September 26. Region 9628 
produced a C4.0 flare at 07:09 UTC. Region 9636 generated a C5.7 flare at 12:24 
UTC. An optically unaccounted M1.8 flare was recorded at 02:58 UTC.
September 25: Region 9628 produced a major M7.6/1N flare at 04:40 UTC with an 
associated moderate type II sweep and likely a geoeffective CME. If there was a 
CME it will probably arrive on September 27.
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 27. If a 
CME associated with a major flare in region 9632 on September 25 arrives active 
to major storm conditions will be likely. 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
      96202001.09.161N12W640070HSX 
      96212001.09.162N14W590140HAX 
      96222001.09.173N13W860180DSO 
      96232001.09.17 N21W74   
      96242001.09.171N02W540090HSX 
      96262001.09.18 N25W66  plage
      96272001.09.189N01W370040DSO 
      96282001.09.1849S18W250730FKCgamma-delta
      96292001.09.19 N26W55  plage
      96322001.09.2021S19W080670EKCbeta-gamma-delta
      96332001.09.221N22E240080HSX 
      96342001.09.227N12E240090DAO 
      96352001.09.239N21W250060DAO 
      96362001.09.2424N14E410400EAIbeta-gamma-delta
      96372001.09.247S15E460210DSO 
      96382001.09.251N03E480020HSX 
      96392001.09.263N04E360030DSO 
      Total number of sunspots:138 

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)
      2001.09230.2 (1)196.6 (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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