Solar Terrestrial Activity Report

Last major update issued on August 23, 2004 at 03:55 UTC.

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

Recent activity

The geomagnetic field was quiet to active on August 22. Solar wind speed ranged between 438 and 548 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 115.2. The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 14.5).
Three hour interval K indices: 33443322 (planetary), 33533322 (Boulder).

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

At midnight there were 6 spotted regions on the visible disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10661 decayed slowly with the largest penumbra showing signs of splitting into two smaller penumbrae.
Region 10662 decayed quickly and could become spotless within a couple of days.
Region 10663 decayed in the trailing spot section. however, new spots emerged near the leading penumbra.
Region 10664 developed early in the day, then began to decay. The opposite polarity areas are well separated and further decay is likely.
New region 10665 emerged on August 20 and was noticed by SEC two days later. The region developed until the early afternoon, afterwards slow decay was observed.

Spotted regions not numbered by NOAA/SEC:
[S448] A new region emerged in the northwest quadrant on August 22, between regions 10665 and 10662. Location at midnight: N09W19

Coronal mass ejections (CMEs)

August 20-22: 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

The northernmost extension of a coronal hole (CH110) in the southern hemisphere was likely in a geoeffective position on August 21.

Processed SOHO/EIT 284 image at 01:06 UTC on August 23. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 23. A weak coronal hole flow from coronal hole CH110 could reach Earth on August 24 and cause unsettled to active conditions that day and on August 25.

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 fair. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela). On other frequencies several stations from Venezuela had fair signals, as did a few stations from the Caribbean (1610, 1620, 1640 (Dom.Republic) and 1660 kHz). From North America signals were fair to good for a few stations with the best signals from CJYQ  930 and WWZN 1510.

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.