Last update issued on September 25, 2003 at 03:55 UTC.
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[Solar cycles 21-23 (last update September 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 1, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update July 23, 2003)]
[Archived reports (last update September 16, 2003)]
The geomagnetic field was active to minor storm on September 24. Solar wind speed ranged between 506 and 751 km/sec under the influence of a high speed stream from coronal hole CH59.
Solar flux measured at 20h UTC on 2.8 GHz was 133.5. The planetary A
index was 33 (STAR Ap - based on the mean of three hour interval ap indices: 34.1).
Three hour interval K indices: 55544444 (planetary), 54443444 (Boulder).
The background x-ray flux is at the class B4 level.
At midnight there were 6 spotted regions on the visible disk. Solar flare activity was low. A total of 12 C class event was recorded during the day.
Region 10463 decayed slowly and quietly.
Region 10464 developed quickly, particularly in the intermediate and trailing spot sections. The region has become large and has major M class flare potential. Two magnetic delta structures formed during the day, a weak one in the southwestern part of the trailing spot section and a stronger one in the western part of the intermediate spot section. Flares: C2.1 at 04:35, C1.2 at 06:26, C5.4/1N at 07:17, C2.0 at 08:55, C1.1 at 10:39, C1.4 at 11:58, C1.9 at 12:54, C1.6 at 15:30 and C1.1 at 23:23 UTC.
Region 10465 decayed slowly and quietly.
Region 10466 increased the penumbral area in the leader spot and was otherwise mostly unchanged and quiet.
Region 10467 developed slowly and was quiet.
Spotted regions not numbered by NOAA/SEC:
[S261] A new region emerged in the southeast quadrant on September 23 and was mostly unchanged on September 24. Location at midnight: S08E06.
September 22-24: No potentially geoeffective CMEs observed. A small filament located mainly in the southwest quadrant erupted between 06 and 09h UTC on September 24. There was no obvious CME associated with this event.
Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
An elongated coronal hole (CH59) in the southern hemisphere was in a geoeffective position on September 18-21. A coronal hole (CH60) in the northern hemisphere will likely rotate into a geoeffective position on September 26-28.
Processed SOHO/EIT 284 image at 01:06 UTC on September 25. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to minor storm on September 25 due to a high speed stream from coronal hole CH59. Quiet to unsettled is likely on September 26-28 with unsettled to active expected for September 29-30 due to a high speed stream from coronal hole CH60.
Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela)].
|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.
Compare to the previous day's image.
Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SEC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SEC or where SEC has observed no spots.
|Solar region||Date numbered||SEC
|Location at midnight||Area||Classification||Comment|
area was 0060
area was 0900
classification was HRX
at midnight, area 0020
classification was DAO
at midnight, area 0040
|Total spot count:||61||76|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2003.03||131.4||61.1||(74.2 predicted, -4.3)|
|2003.04||126.4||60.0||(69.3 predicted, -4.9)|
|2003.05||115.7||55.2||(64.4 predicted, -4.9)|
|2003.06||129.3||77.4||(60.4 predicted, -4.0)|
|2003.07||127.7||85.0||(56.9 predicted, -3.5)|
|2003.08||122.1||72.7||(53.9 predicted, -3.0)|
|2003.09||107.0 (1)||57.0 (2)||(51.9 predicted, -2.0)|
1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (NOAA/SEC) sunspot number. The official international sunspot number is typically 30-50% less.
This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.