Solar Terrestrial Activity ReportSolar Terrestrial Activity Report

Last update September 24, 2001 at 04:00 UTC. Last minor update posted at 11:00 
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 23. Solar wind speed 
ranged between 333 and 568 km/sec. A disturbance began early in the day, peaked 
after noon, and was decreasing in intensity late in the day.
Solar flare activity was moderate. Solar flux was 258.5, the planetary A index 
was 27 (3-hour K indices: 0354 5554, Boulder K indices: 1343 4533). Region 9616 
decayed and rotated partly out of view at the southwest limb. Region 9620 
decayed slowly and quietly. Region 9621 developed slowly and was quiet. Region 
9622 developed slowly and has minor M class flaring potential. Region 9624 was 
quiet and stable, as was region 9627. Region 9628 decayed in the leading spots 
section and developed further in the trailing spots section. Major flares are 
still possible. Region 9629 was mostly unchanged and quiet. Region 9631 decayed 
further and could become spotless today. Region 9632 developed slowly and has a 
large penumbra containing a magnetic delta. The region could produce major 
flares. Region 9633 was quiet and stable. Region 9634 rotated fully into view 
but could be split into two regions. New region 9635 emerged in the northeast 
quadrant. An active region is rotating into view at the southeast limb.
Comment added at 10:30 UTC on September 24: A major long duration event has been 
in progress since 09:25 and is currently still increasing in intensity and is 
now at the X2.5 level. The source of this event is not yet clear, could be 
regions 9628/9632 or a region at the east limb. Further details to follow ... 
Comment added at 11:00 UTC: Region 9632 was the source of the X2.6 long duration 
event which peaked at 10:38 UTC. A significant geoeffective CME may have been 
produced by the event. 
Flares and CMEs
A total of 7 C and 1 M class events were observed on September 23. Region 9622 
produced a C4.4 flare at 01:06 UTC. Region 9628 generated a C3.2 flare at 10:02 
and a C2.5 flare at 15:44 UTC. Region 9632 was the source of an M1.1 flare at 
11:37, a C3.4 flare at 13:59, a C6.5 flare at 14:26 and a C3.3 flare at 23:23 
UTC.
Two full halo CMEs were observed in LASCO C3 images beginning at 16:18 and 21:18 
UTC respectively, both appeared first at the east limb. I haven't been able to 
study EIT images yet, and an evaluation of possible effects on the geomagnetic 
field will have to wait until later today.
September 22: Region 9626 was the source of a moderate type II radio sweep at 
09:24 UTC and a partial halo CME where most of the material was observed over 
the northwest limb. The CME may have geoeffective extensions and could influence 
the geomagnetic field on September 25/26.
The background x-ray flux is at the class C1-C2 level.
Coronal holes
No obvious coronal holes are currently approaching geoeffective positions.
Forecast
The geomagnetic field is expected to be quiet to active on September 24-25. Long 
distance medium wave (AM) band propagation along east-west paths over high and 
upper middle latitudes is fair.
      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
      96162001.09.115S12W770130FSO 
      96172001.09.12 N10W73  plage
      96202001.09.165N12W230100CAO 
      96212001.09.169N14W180220CKO 
      96222001.09.1723N13W450330DKIbeta-gamma
      96232001.09.17 N21W35   
      96242001.09.171N02W130110HSX 
      96252001.09.18 S30W77  plage
      96262001.09.18 N25W27  plage
      96272001.09.186N01E030050DSO 
      96282001.09.1858S18E120720FACbeta-gamma-delta
      96292001.09.198N25W150040DAO 
      96302001.09.20 N27W75  plage
      96312001.09.205N07W570010BXO 
      96322001.09.2017S18E320780DKIbeta-gamma-delta
      96332001.09.221N23E620090HSX 
      96342001.09.224N12E680230FAO 
      96352001.09.233N22E130010BXO 
      Total number of sunspots:145 

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(104.5 predicted, +0.4)
      2001.04177.7108.2(106.0 predicted, +1.5)
      2001.05147.197.3(105.5 predicted, -0.5)
      2001.06173.0134.0(103.8 predicted, -1.7)
      2001.07131.382.2(102.5 predicted, -1.3)
      2001.08162.9106.8(103.1 predicted, +0.6)
      2001.09223.9 (1)166.2 (2)(102.5 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.


      [DX-Listeners' Club] [DX News]