Solar Terrestrial Activity Report

Last major update issued on August 18, 2005 at 05:05 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 active on August 17. Solar wind speed ranged between 592 and 771 (all day average 701) km/sec under the influence of a high speed stream from CH181.

Solar flux measured at 20h UTC on 2.8 GHz was 77.0. The planetary A index was 18 (STAR Ap - based on the mean of three hour interval ap indices: 17.5).
Three hour interval K indices: 44323334 (planetary), 43333324 (Boulder).

The background x-ray flux is at the class A5 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 10797 decayed further and only has a few penumbraless trailing spots outside of the leader spot.
Region 10798 decayed slowly and quietly. A new spot emerged immediately to the west southwest of this region and may have to be split off into a separate region. Magnetograms has this new area with reversed polarities.

Coronal mass ejections (CMEs)

August 15-17: No obvious partly or fully Earth directed CMEs were observed.

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

Recurrent trans equatorial coronal hole (CH181) was in an Earth facing position on August 13-15. A recurrent coronal hole (CH182) in the southern hemisphere was in an Earth facing position on August 17-18. While this coronal hole didn't produce any disturbance during the previous rotation, it has extended somewhat in a northerly direction.

Processed SOHO/EIT 284 image at 19:06 UTC on August 17. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on August 18-19. Some effects from CH182 are possible starting late on August 20 and on August 21, possibly resulting in unsettled to active conditions.

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 poor to fair. Propagation on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela). After LSR there were many signals from Argentina and southern Brazil. 710 Radio Diez and 1120 Rádio Rural were both in with good signals. Before LSR and on the EWE pointed NNW there were a number of stations from North America (800 VOWR and 920 CJCH had the best signals, however, most of the 50 kW stations from the Boston and New York areas were audible as well), the Caribbean (mostly Cuba with 890 having a strong signal) and northern South America (several stations from Colombia including 970 Radio Super and 980 RCN Calí). Overall propagation was much better than expected.

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
10797 2005.08.11 20 6 S14W23 0090 DSO classification was CSO at midnight
10798 2005.08.14 2 3 S09E12 0020 CSO classification was BXO at midnight, area 0010. The westernmost spot could be a separate region
S581 2005.08.12     S10W27     plage
Total spot count: 22 9  
SSN: 42 29  

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 88.1 (1) 33.1 (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]