Solar Terrestrial Activity Report

Last major update issued on September 10, 2005 at 05:20 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 quiet to active on September 9. Solar wind speed ranged between 311 and 549 (all day average 380) km/sec. A solar wind shock was observed at SOHO at 13:10 UTC. This was the arrival of the CME originating from the limb event in region 10808 late on September 7.

Solar flux measured at 17h UTC on 2.8 GHz was 99.2 (the measurements at both 20 and 23h UTC were unusable due to strong flare enhancement). The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 17.0).
Three hour interval K indices: 12014444 (planetary), 32124554 (Boulder).

The background x-ray flux is at the class C1-C2 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was very high. A total of 8 C, 6 M and 3 X class events was recorded during the day.

Region 10808 is large, compact and very complex with 4 magnetic delta structures within the same penumbra. In particular an extreme delta is in the southern central part where an area of negative polarity is nearly completely encircled by positive polarity. In this area there appears to be no separation between the opposite polarity umbrae. Further proton X class flare are very likely. Flares: C6.2 at 00:32, M1.0 at 02:19, M1.1 at 02:36, X1.1 at 03:00, M1.3 at 03:43, M1.8 at 05:03, M6.2/1F at 05:48, C3.7 at 08:26, C3.1 at 09:18, C4.8 at 09:31, X3.6 at 09:59, C3.0 at 12:47, C4.2 at 15:26, C2.8 at 15:43, C1.0 at 16:38, M1.9 at 17:51 and finally a major long duration X6.2/2B proton event peaking at 20:04 UTC. The X6 event was associated with a moderate type II and a strong type IV radio sweep.
Region 10809 was quiet and stable.

Spotted regions not numbered by NOAA/SEC:
[S591] This region emerged in the southeast quadrant on September 9. Location at midnight: S05E25.

Coronal mass ejections (CMEs)

September 8: Another large CME may have been associated with the X5 flare in region 10808 during the evening. This CME could reach Earth on September 10.
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.

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) will rotate to 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 quiet to minor storm on September 10 and active to major storm September 11-22 with severe storming likely on some days due to a near continuous stream of ejected material from region 10808. During the same time interval intense particle storms could have a huge impact on propagation conditions over most middle and high latitude paths.

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 to fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay after midnight, earlier Rádio Rural AM de Parelhas (Brazil). Several weak to fair signals from stations in Argentina and Uruguay were observed.

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 38 34 S09E54 1430 FKC beta-delta
10809 2005.09.08 1 1 N10E47 0020 HRX classification was SX at midnight, area 0030
S591 2005.09.09   1 S05E25 0010 AXX  
Total spot count: 39 36  
SSN: 59 66  

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 83.2 (1) 6.9 (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]