Solar Terrestrial Activity Report

Last major update issued on September 2, 2005 at 06:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update August 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 2, 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 minor storm on September 1. Solar wind speed ranged between 445 and 579 (all day average 510) km/sec under the influence of a high speed stream from CH184.

Solar flux measured at 20h UTC on 2.8 GHz was 79.2. The planetary A index was 21 (STAR Ap - based on the mean of three hour interval ap indices: 21.1).
Three hour interval K indices: 55334222 (planetary), 56334112 (Boulder).

The background x-ray flux is at the class A4 level.

At midnight there were 2 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 10803 reemerged with a couple small spots.
Region 10805 was quiet and stable.

Energetic protons are still enhanced above background levels because of the giant backsided eruption on August 31, that eruption was associated with one of the brightest CMEs observed.

Coronal mass ejections (CMEs)

August 30 and September 1: No obvious partly or fully Earth directed CMEs were observed.
August 31: A faint full halo CME was observed in LASCO images following the long duration C2 event in region 10803 at noon. An extremely bright "mother-of-all-CMEs" full halo CME was observed in LASCO C3 images beginning at 23:18 UTC. Its source was backsided, about 6 days behind the southwest limb.

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 coronal hole (CH184) in the southern hemisphere was in an Earth facing position on August 27-28. A small recurrent coronal hole (CH185) in the northern hemisphere will likely rotate to an Earth facing position on September 1-2. CH185 did not cause any obvious disturbance during the previous rotation.

Processed SOHO/EIT 284 image at 19:06 UTC on September 1. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on September 2 due to a high speed stream from CH184. The halo CME observed at noon on August 31 could reach Earth early on September 3 and cause unsettled to minor storm conditions. Quiet to active is likely on September 4 becoming quiet to unsettled on September 5-6.

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 very poor. Propagation on long distance northeast-southwest paths is fair to good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and LT28 Rafaela Argentina. Propagation to Uruguay and Argentina was good about 30 minutes after LSR with 710 Radio Diez and 950 Radio Belgrano becoming strong in peaks. Radio Sport (Uruguay) was fair on 890 kHz and several other stations were noted, some of them on frequencies not often heard with audio. Some stations from Venezuela were audible after LSR as well while the Peruvians on 1470 and 1499.93 kHz had fair peaks just before LSR.

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
10803 2005.08.24   2 N11W26 0010 BXO  
10804 2005.08.25     N11W78     plage
10805 2005.08.27 2 2 S10E08 0070 HSX classification was CSO at midnight
10806 2005.08.29 2   S16E07 0010 HRX spotless
S588 2005.08.31     N12E16     plage
S589 2005.08.31     S23W59     plage
Total spot count: 4 4  
SSN: 24 24  

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 79.2 (1) 0.8 (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]