Solar Terrestrial Activity Report

Last major update issued on August 30, 2004 at 03:30 UTC. Minor update posted at 10:04 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 August 28, 2004)]
[Archived reports (last update August 25, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on August 29. Solar wind speed ranged between 362 and 461 km/sec. A weak solar wind shock was observed at SOHO at 09:20 UTC. The interplanetary magnetic field was mostly northwards for the remainder of the day, however, the IMF swung southwards early on August 30 and a disturbance is currently in progress.

Solar flux measured at 20h UTC on 2.8 GHz was 86.1. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 9.1).
Three hour interval K indices: 22022333 (planetary), 22122222 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight there was 1 spotted region on the visible disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10663 decayed slowly and quietly.

New region 10666 in the northeast quadrant had spots for a few hours during the day.

Comment added at 10:04 UTC on August 30: The interplanetary magnetic field swung moderately to strongly southwards after 05h UTC. The geomagnetic field is currently at the active to minor storm level, occasional major storm activity is possible. New negative polarity flux emerged inside the leading positive polarity area early today in region 10663. Several spots with penumbra have become visible and further C class flares are possible.

Coronal mass ejections (CMEs)

August 27-29: 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 poorly defined coronal hole (CH111) in the northern hemisphere was in a geoeffective position on August 27-29.

Processed SOHO/EIT 284 image at 01:06 UTC on August 30. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on August 30 - September 1 due to a coronal hole flow.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
Coronal hole indicator CME indicator M and X class flare indicator

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.


Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is good. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: WLAM Lewiston ME. On other frequencies propagation favored signals from North America with strong signals observed on a number of frequencies. The Quebec stations on 1570 and 1610 were both there, however, signals were strongest from stations in the northeastern USA. WNSW Newark NJ and WENE Endicott NY were both good on 1430 kHz.

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.

Active region Date numbered SEC
Location at midnight Area Classification Comment
10663 2004.08.19 4 1 N07W58 0040 CAO classification was HAX
at midnight, area 0030
10664 2004.08.20 1   S11W85 0060 HSX rotated out of view
10666 2004.08.29 1   N16E31 0000 AXX spotless
Total spot count: 6 1
SSN: 36 11

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2003.06 129.3 77.4 65.0 (-2.6)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 60.1 (-1.7)
2003.09 112.2 48.7 59.6 (-0.5)
2003.10 151.7 65.5 58.2 (-1.4)
2003.11 140.8 67.3 56.8 (-1.4)
2003.12 114.9 46.5 54.8 (-2.0)
2004.01 114.1 37.7 52.0 (-2.8)
2004.02 107.0 45.8 (49.1 predicted, -2.9)
2004.03 112.0 49.1 (46.5 predicted, -2.6)
2004.04 101.2 39.3 (44.3 predicted, -2.2)
2004.05 99.8 41.5 (41.0 predicted, -3.3)
2004.06 97.4 43.2 (38.2 predicted, -2.8)
2004.07 119.1 51.0 (36.3 predicted, -1.9)
2004.08 111.0 (1) 68.2 (2) (34.9 predicted, -1.4)

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.

[DX-Listeners' Club]