Solar Terrestrial Activity Report

Last major update issued on August 22, 2007 at 04:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update July 23, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 23, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 23, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update July 1, 2007)]

Recent activity

The geomagnetic field was quiet on August 21. Solar wind speed ranged between 285 and 347 km/s (average speed was 331 km/s, decreasing 26 km/s from the previous day). Weak coronal hole effects were observed until about 17h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 69.3. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.0). Three hour interval K indices: 21012101 (planetary), 21212111 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

New region 10969 rotated into view at the southeast limb.

Coronal mass ejections (CMEs)

August 19-21: No obvious fully or partly Earth directed CMEs were observed.

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 recurrent trans equatorial coronal hole (CH287) will be in an Earth facing position on August 21-24.

.

Processed STEREO 195 image at 21:45 UTC on August 21. The darkest areas on the solar disk are likely coronal holes.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Monitoring remarks from a location near N58E06: August 21: TA signals were significantly weaker compared to the previous night with the best signals noted from New York stations 1010 WINS, 1050 WEPN and 1130 WBBR.

Forecast

The geomagnetic field is expected to be quiet on August 22-24. Quiet to active is likely on August 25-28 due to effects from CH287.

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.

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
10969 2007.08.21 1 2 S06E73 0090 HSX  
Total spot count: 1 2  
SSN: 11 12  

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)
2006.06 76.5 13.9 16.3 (-1.0)
2006.07 75.7 12.2 15.3 (-1.0)
2006.08 79.0 12.9 15.6 (+0.3)
2006.09 77.8 14.4 15.6 (+0.0)
2006.10 74.3 10.4 14.2 (-1.4)
2006.11 86.3 21.5 12.7 (-1.5)
2006.12 84.5 13.6 12.1 (-0.6)
2007.01 83.3 16.9 12.0 (-0.1)
2007.02 77.7 10.6 (11.6 predicted, -0.4)
2007.03 72.2 4.8 (11.1 predicted, -0.5)
2007.04 72.4 3.7 (10.8 predicted, -0.3)
2007.05 74.4 11.7 (10.4 predicted, -0.4)
2007.06 73.7 12.0 (10.3 predicted, -0.1)
2007.07 71.6 10.0 (10.5 predicted, +0.2)
2007.08 68.5 (1) 5.7 (2) (11.0 predicted, +0.5)

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.


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