Solar Terrestrial Activity Report

Last major update issued on October 11, 2007 at 01:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update October 4, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update October 3, 2007)]

Recent activity

The geomagnetic field was very quiet on October 10. Solar wind speed ranged between 278 and 306 km/s (average speed was 289 km/s, decreasing 3 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 68.1. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.6). Three hour interval K indices: 01101101 (planetary), 01201010 (Boulder).

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

At midnight the visible solar disk was spotless. The solar flare activity level was very low. No C class events were recorded during the day.

Coronal mass ejections (CMEs)

October 8-10: No obvious fully or partly Earth directed CMEs were observed in LASCO imagery.

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 coronal hole (CH294) in the southern hemisphere was in an Earth facing position on October 8-10. CH294 has become better defined over the last solar rotation, although most of the coronal hole is too far to the south to influence Earth. A recurrent trans equatorial hole (CH295) will likely rotate into an Earth facing position on October 14-17. CH295 is poorly defined in the western part. The development of an active region in the southeastern part of the coronal hole has diminished its area significantly.

Processed SOHO/EIT 195 image at 00:00 UTC on October 11. The darkest areas on the solar disk are likely coronal holes.


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

Monitoring remarks from a location near N58E06: October 9-10: Listening started at 21:30 UTC. Although several east coast USA stations became audible before 22h UTC, signals were a little weaker than one day earlier. Still 1500 WFIF was heard with a fair signal before signing off. During the morning of October 10 propagation was excellent to the USA east coast favoring stations from Massachusetts (1340 WNBH was heard for the first time and had good peaks) and Florida (1230 had WONN with a strong signal and was only occasionally topped by WSBB, 1240 was dominated by WMMB with WFOY present a few times). WSUA Miami on 1260 was like a local station at times. The best Trans Atlantic propagation sector was 270-290 degrees.


The geomagnetic field is expected to be mostly quiet October 11-16, a few unsettled and active intervals are possible on October 11-13 due to effects from CH294. Some unsettled to active intervals are likely on October 17-21 due to a high speed stream from CH295.

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
Location at midnight Area Classification Comment
10972 2007.10.06     S06W58     plage
Total spot count: 0 0  
SSN: 0 0  

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)
2006.08 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 (-0.4)
2007.03 72.2 4.8 10.8 (-0.8)
2007.04 72.4 3.7 (10.1 predicted, -0.7)
2007.05 74.4 11.7 (9.0 predicted, -1.1)
2007.06 73.7 12.0 (8.0 predicted, -1.0)
2007.07 71.6 10.0 (7.3 predicted, -0.7)
2007.08 69.1 6.2 (6.8 predicted, -0.5)
2007.09 67.1 2.4 (6.9 predicted, +0.1)
2007.10 67.8 (1) 1.3 (2) (7.6 predicted, +0.7)

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]