Solar Terrestrial Activity Report

Last major update issued on September 3, 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 to unsettled on September 2. Solar wind speed ranged between 446 and 495 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 93.9. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.8).
Three hour interval K indices: 22332223 (planetary), 22332112 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there was one spotted region 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. There's lots of bright plage to the south and east of the single penumbra.

Coronal mass ejections (CMEs)

August 31 - September 2: No obviously Earth directed CMEs were observed.

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 likely rotate into a geoeffective position on September 3-4.

Processed SOHO/EIT 284 image at 01:06 UTC on September 3. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on September 3-5. For September 6 and 7 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 poor. Propagation along long distance north-south paths is poor to fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a weak signal- Radio Vibración (Venezuela) was noted at times. On other frequencies propagation was best near midnight UTC with Puerto Rico noted on 1430, 1480, 1520, 1600 and 1660 kHz. Several stations from Venezuela had fair signals as well. WWZN Boston on 1510 kHz and Greenland on 650 kHz were the only stations noted from North America. At local sunrise on September 2 propagation favored Venezuela and Colombia with stations on many frequencies.

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.