Solar Terrestrial Activity Report

Last major update issued on October 29, 2006 at 05:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 2, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 2, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 2, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update October 2, 2006)]

Recent activity

The geomagnetic field was quiet to active on October 28. Solar wind speed ranged between 299 and 552 km/s (all day average 380 km/s - increasing 71 km/s over the previous day) under the influence of a high speed stream from CH245.

Solar flux measured at 20h UTC on 2.8 GHz was 74.7. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 13.9). Three hour interval K indices: 12342334 (planetary), 13342324 (Boulder).

The background x-ray flux is at the class A2 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 10919 decayed and could become spotles today.
New region  10920 emerged near the southwest limb.

Coronal mass ejections (CMEs)

October 26-28: No obvious partly or fully Earth directed CMEs were detected 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 fragmented trans equatorial coronal hole structure (CH245) was in an Earth facing position on October 24-26. The extension into the northern hemisphere is poorly defined. Recurrent coronal hole (CH246) will likely rotate into an Earth facing position on October 31. A new coronal hole formed in the northern hemisphere (just north of the equator and near the central meridian in the northwest quadrant) on October 28.

Processed SOHO/EIT 284 image at 01:06 UTC on October 28. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to minor storm on October 29 due to effects from CH245 becoming quiet to unsettled on October 30. Effects from a new coronal hole could reach Earth on October 31 and cause unsettled or active intervals. Mostly quiet conditions are likely on November 1-2 while some unsettled and active intervals are possible on November 3 when the stream from CH246 arrives.

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.


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 to poor.

Monitoring remarks from a location near N58E06: At 03h UTC a few signals from North America were still present, then at 05h UTC no signals from that area were audible. Only a few stations from Colombia and Venezuela were present on low frequencies at that time.

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
10919 2006.10.27 3 1 S15W15 0020 BXO classification was AXX at midnight, area 0000
10920 2006.10.28 5 4 S07W82 0150 ESO classification was CSO at midnight, area 0040
Total spot count: 8 5  
SSN: 28 25  

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)
2005.08 90.5 36.4 27.4 (-1.7)
2005.09 91.1 21.9 25.8 (-1.6)
2005.10 77.0 8.7 25.5 (-0.3)
2005.11 86.3 18.0 24.9 (-0.6)
2005.12 90.7 41.1 23.0 (-1.9)
2006.01 83.4 15.3 20.8 (-2.2)
2006.02 76.5 4.9 18.6 (-2.2)
2006.03 75.4 10.6 17.3 (-1.3)
2006.04 89.0 30.2 (17.1 predicted, -0.2)
2006.05 80.9 22.2 (16.8 predicted, -0.3)
2006.06 76.5 13.9 (15.1 predicted, -1.7)
2006.07 75.7 12.2 (13.2 predicted, -1.9)
2006.08 79.0 12.9 (12.8 predicted, -0.4)
2006.09 77.8 14.5 (12.6 predicted, -0.2)
2006.10 74.1 (1) 14.2 (2) (11.6 predicted, -1.0)

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]