Solar Terrestrial Activity Report

Last major update issued on October 24, 2006 at 04:10 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 very quiet on October 24. Solar wind speed ranged between 463 and 556 km/s (all day average 499 km/s - decreasing 57 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 76.4. 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: 10011111 (planetary), 10012222 (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 10917 decayed quickly and quietly.
New region 10918 emerged just west of region 10917.

Coronal mass ejections (CMEs)

October 21-23: 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 large Y-shaped trans equatorial coronal hole (CH245) - where the southwestern part was formerly CH241 - will be in an Earth facing position on October 24-25. The central part is poorly defined.

Processed SOHO/EIT 284 image at 19:06 UTC on October 23. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet on October 24-26. On October 27-29 quiet to active conditions are likely due to effects from CH245.

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.

Propagation

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

Monitoring remarks from a location near N58E05: A number of strong signals were heard from stations along the east coast of North America, particularly stations from Florida and New York were impressive. Not often received stations like 980 WHSR and 1020 WRHB were easily audible.

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.

Monthly solar cycle data

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.