Solar Terrestrial Activity Report

Last major update issued on October 31, 2006 at 04:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 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 unsettled on October 30. Solar wind speed ranged between 437 and 570 km/s (all day average 510 km/s - decreasing 9 km/s from the previous day) under the influence of a high speed stream from CH245.

Solar flux measured at 20h UTC on 2.8 GHz was 75.7. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 8.6). Three hour interval K indices: 32232212 (planetary), 32242221 (Boulder).

The background x-ray flux is at the class A8 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.

New region 10921 rotated into view at the southeast limb on October 29 and was numbered the next day by NOAA/SEC. The region developed quickly on October 30 and is capable of C class flaring. Currently the separation between the opposite polarity areas is poor.

Spotted regions not numbered by NOAA/SEC:
Region S678 emerged in the southeast quadrant on October 30.

Coronal mass ejections (CMEs)

October 28-30: 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

Recurrent coronal hole (CH246) in the northern hemisphere was in an Earth facing position on October 30-31. 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 31. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on October 31 - November 1 while some unsettled and active intervals are possible on November 2 or 3 when the stream from CH246 arrives.

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 poor to fair. Propagation on long distance northeast-southwest paths is poor.

Monitoring remarks from a location near N58E06: At 01h UTC a number of stations from the east coast of North America were audible with poor to fair signals. Later on propagation favored stations further south, primarily from Cuba, Venezuela and Colombia.

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.