Solar Terrestrial Activity Report

Last major update issued on September 10, 2006 at 04:25 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, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 3, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 3, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update September 8, 2006)]

Recent activity

The geomagnetic field was inactive to very quiet on September 9. Solar wind speed ranged between 339 and 349 km/s (all day average 346 km/s - decreasing 26 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 85.5. The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.0). Three hour interval K indices: 11000001 (planetary), 12010010 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10907 reemerged with a few tiny spots.
Region 10908 was mostly unchanged and quiet.
Region 10909 added a few more spts in the leading spot section while slow decay was observed in the trailing spots.

Coronal mass ejections (CMEs)

September 7 and 9: No obvious partly or fully Earth directed CMEs were detected in incomplete LASCO imagery.
September 8: While there were mayn data gaps some of the LASCO images from early in the day and around noon  displays CMEs in progress. Based on the scant evidence available it is hard to tell if these CMEs had a frontsided origin.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A small recurrent coronal hole (CH239) in the southern hemisphere will likely rotate into an Earth facing position on September 14.

Processed SOHO/EIT 284 image at 19:08 UTC on August 18. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on September 10-16. There is a slight chance of CME effects reaching Earth on September 11. Weak coronal hole effects are possible on September 17.

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. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at 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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is good. Many stations from North America were heard with good to excellent signals. Most of the staitons observed were from the northeastern US. Some longer range propagation was noted as well with one surprise being 1310 Radio María Panamá. Propagation on long distance northeast-southwest paths is very poor.

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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10907 2006.09.05 4 3 S13W08 0020 DSO classification was BXO at mindight, area 0010
10908 2006.09.05 3 4 S15E19 0240 CKO  
10909 2006.09.06 14 11 S08W17 0080 DSI  
Total spot count: 21 18  
SSN: 51 48  

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)
2005.07 96.4 40.1 29.1 (+0.3)
2005.08 90.5 36.4 27.4 (-1.7)
2005.09 91.1 21.9 25.8 (-1.6)
2005.10 77.0 8.5 25.5 (-0.3)
2005.11 86.3 18.0 24.9 (-0.6)
2005.12 90.7 41.2 23.0 (-1.9)
2006.01 83.4 15.4 20.8 (-2.2)
2006.02 76.5 4.7 18.6 (-2.2)
2006.03 75.4 10.8 (17.1 predicted, -1.5)
2006.04 89.0 30.2 (16.4 predicted, -0.7)
2006.05 80.9 22.2 (15.9 predicted, -0.5)
2006.06 76.5 13.9 (14.1 predicted, -1.8)
2006.07 75.7 12.2 (12.4 predicted, -1.7)
2006.08 79.0 12.9 (11.9 predicted, -0.5)
2006.09 81.3 (1) 8.9 (2) (11.9 predicted, -0.0)

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% 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]