Solar Terrestrial Activity Report

Last major update issued on August 7, 2005 at 05:10 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 3, 2005)]

Recent activity

The geomagnetic field was unsettled to minor storm on August 6. Solar wind speed ranged between 451 and 803 (all day average 540) km/sec. A high speed stream from CH178B ended sometime after noon, however, another and significantly higher speed stream dominated the solar wind after 15h UTC. This may have been the arrival of the stream associated with CH178.

Solar flux measured at 20h UTC on 2.8 GHz was 93.4. The planetary A index was 34 (STAR Ap - based on the mean of three hour interval ap indices: 33.9).
Three hour interval K indices: 55554343 (planetary), 45444443 (Boulder).

The background x-ray flux is at the class B1 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 10792 decayed further with some loss of penumbral area. New small spots emerged immediately to the north and northwest of the main spot.
Region 10794 decayed slowly and quietly.
Region 10795 developed slowly as new trailing spots emerged.

Coronal mass ejections (CMEs)

August 4 and 6: No obvious partly or fully Earth directed CMEs were observed.
August 5: A filament eruption across the central meridian in the northern hemisphere was triggered by the C2 LDE in region 10792 during the morning. At least a partial halo CME was observed after this event.

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 small trans equatorial coronal hole (CH178) became less obvious on August 4 when it would have been in an Earth facing position. This was probably due to coronal outflow from nearby region 10796. A small, elongated coronal hole (CH179) in the northern hemisphere was in an Earth facing position on August 5-6. CH179 apparently disappeared on August 6. A poorly defined coronal hole (possibly even just weak corona) - CH180 - will rotate to an Earth facing position on August 8-9.

Processed SOHO/EIT 284 image at 01:06 UTC on August 7. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be unsettled to minor storm on August 7-8 due to coronal hole and CME effects.  Quiet to unsettled is likely on August 9-10. 

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. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela),  Radio Cristal del Uruguay and CPN Radio (Perú). Propagation was unusual with Argentinean stations on frequencies above 1500 kHz heard better on the EWE directed towards the NNW than on the quasi BOG directed towards the southwest. Propagation was best above 1350 kHz with interesting carriers on several frequencies. Frequencies like 1450 and 1460 kHz had unidentified stations from Brazil. From North America VOCM on 590, CJYQ on 930 and WWZN on 1510 kHz all had weak to fair signals.

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
10792 2005.07.28 9 9 N10W41 0130 CSO classification was CAO at midnight , area 0090
10794 2005.07.31 11 11 S12W10 0220 DHO beta-gamma
classification was DAO at midnight, area 0170
10795 2005.07.31 4 4 N12E00 0070 CSO  
10796 2005.08.03     S07W34     plage
Total spot count: 24 24  
SSN: 54 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 29.1 (33.5 predicted, -1.1)
2005.03 89.9 24.8 (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 39.3 (26.1 predicted, -1.5)
2005.07 96.4 39.9 (25.1 predicted, -1.0)
2005.08 104.7 (1) 17.0 (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]