Solar Terrestrial Activity Report

Last update issued on September 7, 2003 at 04:00 UTC. 

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 1, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update July 23, 2003)]
[Archived reports (last update August 28, 2003)]

Recent activity

The geomagnetic field was quiet to unsettled on September 6. Solar wind speed ranged between 548 and 659 km/sec under the weakening influence of a high speed stream from coronal hole CH54.

Solar flux measured at 20h UTC on 2.8 GHz was 104.9. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 13.1).
Three hour interval K indices: 32333332 (planetary), 32332432 (Boulder).

The background x-ray flux is at the class B2-B3 level.

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was very low.

Region 10450 developed slowly as some new spots emerged.
Region 10453 decayed slowly and quietly.
Region 10454 decayed slowly and quietly.
New region 10455 emerged early in the day in the southeast quadrant, decayed and had only a single tiny spot left by the end of the day.

Coronal mass ejections (CMEs)

September 4-6: No potentially geoeffective CMEs 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 trans equatorial coronal hole (CH55) will rotate into a geoeffective position on September 6-8.

Processed SOHO/EIT 284 image from 01:06 UTC on September 7. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on September 8 while September 9-11 could see unsettled to minor storm conditions due to a high speed stream from coronal hole CH55.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor to fair. Propagation along north-south paths is fair to good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay].

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.
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.

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.

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 sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.