Solar Terrestrial Activity Report

Last major update issued on October 16, 2008 at 02:20 UTC. Until October 26 updates are likely to be posted at irregular times, if at all, as I will be at a remote location.

[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 4, 2008)]

The geomagnetic field was quiet to unsettled on October 15. Solar wind speed ranged between 322 and 369 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 70.9. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5). Three hour interval K indices: 23321212 (planetary), 23321211 (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.

Region 11005 decayed slowly and quietly.

October 13-15: No partially or fully Earth directed CMEs were observed in LASCO imagery.

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 small, poorly defined recurrent coronal hole (CH344) in the northern hemisphere will likely rotate into an Earth facing position on October 16. No geomagnetic effects were noted from this coronal hole during the previous rotation.

Processed SOHO/EIT 195 image at 00:24 UTC on October 16. 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 fair. Propagation on long distance northeast-southwest paths is poor to fair.

The geomagnetic field is expected to be mostly quiet on October 16-26. There is a chance of a few unsettled intervals due to effects from CH344 on October 19-20.

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/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

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/SWPC) 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.