Solar Terrestrial Activity Report

Last major update issued on August 31, 2005 at 03:35 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 August 13, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on August 30. Solar wind speed ranged between 340 and 389 (all day average 352) km/sec. Solar wind data from ACE suggest that the stream from CH184 began at about 18h UTC. The coronal hole effects have so far been minor.

Solar flux measured at 20h UTC on 2.8 GHz was 86.0. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4).
Three hour interval K indices: 10001132 (planetary), 00100032 (Boulder).

The background x-ray flux is at the class A8 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 1 C class event was recorded during the day.

Region 10803 lost all remaining penumbra and has become a simple structured region with only small spots. The region could soon become spotless.
Region 10805 developed slowly and was quiet.
Region 10806 decayed slightly and was quiet. Flare: C1.4 at 04:23 UTC.

Coronal mass ejections (CMEs)

August 28-30: No obvious partly or fully Earth directed CMEs were observed. A large full halo CME was observed from a source behind the southwest limb on August 29. A minor increase in the above 10 MeV proton flux was probably caused by this event as well.

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 likely 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 August 30. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to minor storm on August 31 and September 1 due to a high speed stream from CH184. Quiet to unsettled is likely on September 2-4.

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 was fair before 03h UTC, and is currently poor. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: WLAM Lewiston ME before 03h UTC, then Radio Vibración (Venezuela) with Radio Cristal del Uruguay slowly taking over. WWZN on 1510 had strong peaks and several other stations from the northeastern USA and the Canadian Atlantic provinces had fair signals. However signals had deep and long fades and most of them had gone by 03:30 UTC, replaced by signals from further south.

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
10801 2005.08.20     N09W70     plage
10802 2005.08.24     S12W65     plage
10803 2005.08.24 19 7 N11E01 0040 DAI classification was BXO at midnight, area 0010
10804 2005.08.25     N11W52     plage
10805 2005.08.27 5 5 S08E34 0050 DSO classification was DAO at midnight, area 0070
10806 2005.08.29 14 12 S17E37 0060 DAI beta-gamma
area was 0040 at midnight
Total spot count: 38 24  
SSN: 68 54  

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)
2004.06 97.4 43.2 41.6 (-2.2)
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 (33.5 predicted, -1.1)
2005.03 89.9 24.5 (32.1 predicted, -1.4)
2005.04 86.0 24.4 (30.2 predicted, -1.9)
2005.05 99.3 42.6 (27.6 predicted, -2.6)
2005.06 93.7 39.6 (26.1 predicted, -1.5)
2005.07 96.4 39.9 (25.1 predicted, -1.0)
2005.08 90.8 (1) 64.0 (2) (23.2 predicted, -1.9)

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]