Solar Terrestrial Activity Report

Last major update issued on October 28, 2006 at 05:15 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 on October 27. Solar wind speed ranged between 276 and 359 km/s (all day average 309 km/s - decreasing 57 km/s from the previous day). Solar wind speed began to increase slowly after 19h UTC as the first parts of the stream from CH245 arrived. Average solar wind density for the day was the highest I've seen recorded by SOHO. The associated geomagnetic disturbance has so far been very weak.

Solar flux measured at 20h UTC on 2.8 GHz was 72.0. The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.1). Three hour interval K indices: 10010012 (planetary), 11011122 (Boulder).

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

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

New region 10919 emerged in the southern hemisphere near the central meridian. The region has an east-west oriented inversion line and could develop further.

Coronal mass ejections (CMEs)

October 25-27: 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-November 1.

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

Forecast

The geomagnetic field is expected to be quiet to active on October 28-29 due to effects from CH245. Mostly quiet conditions are likely on October 30 - November 2 while some unsettled and active intervals are possible on November 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 good. Propagation on long distance northeast-southwest paths is poor.

Monitoring remarks from a location near N58E06: Lots of stations from North America were heard during the night. Signals from the USA arrived as early as 21:45 UTC. At 05h UTC on October 28 the best signals were heard from stations along the east coast and from the Great Lakes. Above 1200 kHz some stations from Venezuela and Colombia were present, occasionally with good signals.

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.