Solar Terrestrial Activity Report

Last major update issued on September 9, 2004 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 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 slightly active on September 8. Solar wind speed ranged between 349 and 456 km/sec under the influence of a fairly low speed stream from coronal hole CH112. This influence cam to end after noon.

Solar flux measured at 20h UTC on 2.8 GHz was 124.5. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 10.1).
Three hour interval K indices: 23423222 (planetary), 23422221 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 4 spotted regions on the visible disk. The solar flare activity level was low. A total of 3 C class events was recorded during the day.

Region 10667 decayed slightly and was quiet.
Region 10669 developed further, particularly in the leading spot section. A positive polarity spot has emerged at the southern edge of the main penumbra and has created a weak magnetic delta structure. Flare: C1.0 at 20:02 UTC.
Region 10671 developed further and could produce minor M class flares.

Spotted regions not numbered by NOAA/SEC:
[S451] This region emerged in the southeast quadrant on September 8 with a single small spot. Location at midnight: S06E53.

Two closely spaced regions are about to rotate into view at the northeast limb. M class flares are possible. The southernmost of these regions has been the most active. Flares: C1.5 at 01:10 and C1.2 at 22:22 UTC.

Coronal mass ejections (CMEs)

September 6-8: No obviously Earth directed CMEs were observed. A full halo CME was observed after the C2 event behind the northeast limb on September 7.

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 coronal hole (CH113) in the southern hemisphere could rotate into a geoeffective position on September 12.

Processed SOHO/EIT 284 image at 01:06 UTC on September 9. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on September 9-11.

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 to occasionally fair. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela) with a weak signal. As during the previous night most of the stations observed on other frequencies were from North America. Canadian stations were heard on 590, 710, 780, 800, 920, 930, 950, 960, 1070, 1140 and 1400 kHz with US stations coming in on 880, 1010, 1030, 1050, 1130, 1500, 1510, 1560 and 1660 kHz. The best signals were from 800 VOWR and 930 CJYQ.

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.