Solar Terrestrial Activity Report

Last major update issued on October 1, 2004 at 01:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update August 28, 2004)]
[Archived reports (last update September 27, 2004)]

Recent activity

The geomagnetic field was quiet on September 30. Solar wind speed ranged between 342 and 376 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 88.2. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.9).
Three hour interval K indices: 21001222 (planetary), 11002111 (Boulder).

The background x-ray flux is at the class A5 level.

At midnight there were 2 spotted regions on the visible disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10675 was quiet and stable.
Region 10676 was quiet and stable.
New region 10677 emerged in the northeast quadrant on September 29 and was numbered the next day by SEC. The region then decayed and was spotless by midnight.

Coronal mass ejections (CMEs)

September 28-30: No obviously earth directed CMEs observed (no new LASCO images since September 26).

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

No obvious coronal holes are currently approaching geoeffective positions.

Processed SOHO/EIT 284 image at 19:06 UTC on September 10. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on October 1-3. There is a possibility of a recurrent coronal hole flow reaching Earth on October 2, however, no evidence of a coronal hole has been observed in recent images.

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) Material from a CME is likely to impact 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 to very good. Propagation along long distance north-south paths is very poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: WLAM Lewiston ME. At least 2 other stations from the USA were observed on the frequency. A number of strong signals were heard from North American stations throughout the MW band. Greenland on 650 kHz was very impressive, as were several New York and Montreal stations. KWHN dominated 1650 kHz instead of often heard Radio Disney.

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% less.

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.