Solar Terrestrial Activity Report

Last major update issued on September 4, 2004 at 03:40 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 August 25, 2004)]

Recent activity

The geomagnetic field was quiet on September 3. Solar wind speed ranged between 339 and 452 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 96.7. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 4.3).
Three hour interval K indices: 21101211 (planetary), 12121010 (Boulder).

The background x-ray flux is at the class B1 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 10667 was quiet and stable.
New region 10668 emerged early in the day in the southwest quadrant and has developed quickly.

Coronal mass ejections (CMEs)

September 1-3: No obviously Earth directed CMEs were observed. Two full halo CMEs were observed on September 3, both from a centrally placed backsided source.

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

A recurrent coronal hole (CH112) in the northern hemisphere will be in a geoeffective position on September 3-5.

Processed SOHO/EIT 284 image at 01:06 UTC on September 4. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet on September 4-5. For September 6-8 unsettled to active conditions are likely due to a high speed stream from coronal hole CH112.

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 very poor. Propagation along long distance north-south paths is poor at night and good near local sunrise. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). Only a few other stations were noted (Radio Fé y Alegria on 1390 and Radio Bahia on 1430, both from Venezuela, and WDHP on 1620 kHz). During local sunrise on September 3 propagation was excellent towards eastern Brazil, Uruguay and Argentina. From Brazil Rádio Tapense (Rio Grande do Sul) on 1500 kHz and Rádio Educadora (Bahía) on 1560 kHz were the most interesting stations, while Radio Rural (Montevideo, Uruguay) on 610 kHz was better than I've heard them before.

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.