Solar Terrestrial Activity Report

Last major update issued on September 12, 2005 at 04:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 3, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 3, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 3, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update September 2 , 2005)]

Recent activity

The geomagnetic field was active to extremely severe storm on September 11. Solar wind speed ranged between 615 and 1004 (all day average 880) km/sec. A solar wind shock was observed at SOHO at 00:49 UTC when the  CME associated with the X6 event in region 10808 on September 9 arrived. The transit time was only 29 hours.

Solar flux measured at 20h UTC on 2.8 GHz was 109.2. The planetary A index was 105 (STAR Ap - based on the mean of three hour interval ap indices: 105.3).
Three hour interval K indices: 57976554 (planetary), 56965444 (Boulder).

The background x-ray flux is at the class B8 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 6 C and 3 M class events was recorded during the day.

Region 10808 continued to decay somewhat in the easternmost parts as the negative polarity areas there became weaker. Many new small spots emerged in the dominant positive polarity areas. There is still a significant magnetic delta structure within the largest penumbra. When this region first emerged as region 10798 it was a reversed polarity region. Now most of the negative polarity has migrated to the western parts of the region. Once the process of straightening out the polarity alignment completes the region will lose much of its flare potential. There is still a chance of very energetic X class proton flares. Flares: M3.4 at 02:35, C7.1 at 06:18, C4.4 at 07:10, C3.1 at 10:18, M3.0/1F long duration event peaking at 13:12, M1.3 at 20:40, C1.9 at 22:08, C6.5 at 22:15 and C2.0 at 23:25 UTC.
Region 10809 decayed and could soon become spotless.

Coronal mass ejections (CMEs)

September 9: LASCO C2 and C3 images are again available, however, they are strongly contaminated by the ongoing proton storm. Several CMEs (where the main body of the ejected material is not aimed at Earth) are likely to have been produced by the multitude of M and X class events in region 10808. Glancing impacts are possible on September 11. The CME associated with the long duration X6 event is likely to be more significant than the others.
September 10: Another large, fast full halo CME was associated with the X2 long duration event in region 10808 late in the day.
September 12: At least a partial halo CME was associated with an M3 LDE in region 10808 just after noon.

Coronal holes

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

A recurrent trans equatorial coronal hole (CH187) was in an Earth facing position on September 9-11.

Processed TRACE mosaic image on September 6, 2005. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be active to severe storm on September 12 and unsettled to major storm on September 13.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
Coronal hole indicator CME indicator M and X class flare indicator

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
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.


Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is useless. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a weak signal. Only a few other signals were audible, all of them from Argentina, Uruguay and southern Brazil.

Active solar regions (Recent map)

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. SEC active region numbers in the table below and in the active region map above are the historic SEC/USAF numbers.

Active region Date numbered SEC
Location at midnight Area Classification Comment
10808 2005.09.07 80 62 S09E30 1250 EKC beta-gamma-delta
10809 2005.09.08 1 2 N10E20 0020 HSX classification was AXX at midnight, area 0010
S591 2005.09.09     S05W01     plage
Total spot count: 81 64  
SSN: 101 84  

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2004.07 119.1 51.1 40.2 (-1.4)
2004.08 109.6 40.9 39.2 (-1.0)
2004.09 103.1 27.7 37.5 (-1.7)
2004.10 105.9 48.0 35.9 (-1.6)
2004.11 113.2 43.5 35.3 (-0.6)
2004.12 94.5 17.9 35.2 (-0.1)
2005.01 102.2 31.3 34.6 (-0.6)
2005.02 97.2 29.2 33.9 (-0.7)
2005.03 89.9 24.5 (33.5 predicted, -0.4)
2005.04 86.0 24.4 (32.2 predicted, -1.3)
2005.05 99.3 42.6 (29.9 predicted, -2.3)
2005.06 93.7 39.6 (28.7 predicted, -1.2)
2005.07 96.4 39.9 (27.7 predicted, -1.0)
2005.08 90.5 36.4 (25.8 predicted, -1.9)
2005.09 88.6 (1) 12.3 (2) (24.2 predicted, -1.6)

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% lower.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.

[DX-Listeners' Club]