Solar Terrestrial Activity Report

Last major update issued on July 6, 2004 at 04:15 UTC. Due to vacation there will be no further updates until July 26.

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

Recent activity

The geomagnetic field was quiet to unsettled on July 5. Solar wind speed ranged between 394 and 467 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 78.2 (the lowest solar flux since the end of the last solar minimum). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.9).
Three hour interval K indices: 21012233 (planetary), 12012222 (Boulder).

The background x-ray flux is at the class A3 level.

At midnight there were 2 spotted regions on the visible disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10639 decayed slowly and quietly.
Region 10640 reemerged with spots.

Coronal mass ejections (CMEs)

July 3-5: No obviously earth directed CMEs were detected. An impressive full halo CME was observed late on July 5. Ejected material was first observed below the south pole in C3 images at 23:18 UTC and surrounded the entire disk shortly after midnight. This CME is likely to have had a backsided origin, about 7 days behind the southwest limb.

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

No significant coronal holes are currently approaching geoeffective positions.

Processed SOHO/EIT 284 image at 01:06 UTC on July 6. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on July 5-9.

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 poor. Propagation along long distance north-south paths is good. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. Radio Vibración was noted as well at times. Post sunrise propagation was interesting with stations from the Buenos Aires area peaking about half an hour after sunrise (Radio Chascomus on 1520 kHz was noted), then swung slightly northwards one hour after sunrise. At that time Radio Ñandutí (Asunción, Paraguay) had an amazingly good signal on 1020.1 kHz and there was another Paraguayan on 970 kHz. From North America WWZN on 1510 kHz was there again with a fair signal, otherwise Newfoundland was heard on 590 and 800 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
10639 2004.06.27 5 4 N08W35 0020 BXO single polarity spots
classification was HRX
at midnight
10640 2004.06.27 1 3 S08W39 0030 AXX area was 0010
at midnight
10641 2004.07.04     N14E41     plage
Total spot count: 6 7
SSN: 26 27

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 (51.1 predicted, -3.7)
2004.02 107.0 45.8 (46.9 predicted, -4.2)
2004.03 112.0 49.1 (44.1 predicted, -2.8)
2004.04 101.2 39.3 (42.1 predicted, -2.0)
2004.05 99.8 41.5 (38.8 predicted, -3.3)
2004.06 97.4 43.2 (36.0 predicted, -2.8)
2004.07 79.8 (1) 4.9 (2) (34.2 predicted, -1.8)

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]