Solar Terrestrial Activity Report

Last major update issued on July 30, 2004 at 04:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update July 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 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 29. Solar wind speed ranged between 461 and 638 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 99.7. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.8).
Three hour interval K indices: 23322322 (planetary), 33322332 (Boulder).

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

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

Region 10652 decayed and rotated partly out of view at the northwest limb. A minor M class flare may be possible today. Flares: C1.1 at 06:26, C1.7 at 07:05, long duration C2.1 peaking at 13:04 and C2.8 at 16:33 UTC.
Region 10654 developed as new positive polarity flux emerged just ahead of the trailing negative polarity spots. C flares are possible.

Spotted regions not numbered by SEC/NOAA:
[S440] A new region rotated into view at the southeast limb on July 29. Although the region is close to the limb it appears as if the positive and negative polarity fields are narrowly separated. The region may be capable of C class flaring.

Coronal mass ejections (CMEs)

July 27, 29: No obvious Earth directed CMEs observed.
July 28: A partial halo CME was observed after a very long duration event in region 10652 early in the day. There is a chance that some effects from this CME could be observed at Earth on July 30.

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 obvious coronal holes are currently approaching geoeffective positions.

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


The geomagnetic field is expected to be mostly quiet to unsettled on July 30 - August 2. There is a chance of unsettled to active conditions on July 30 if the CME observed on July 27 reaches Earth.

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 very poor. Propagation along long distance north-south paths is poor to very good (see explanation below). Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a poor signal before local sunrise. Propagation improved quickly after local sunrise and was at its best 30-60 minutes past sunrise. Argentina was the favored country with stations on unusual frequencies like 670, 1490 and 1550 kHz noted. Radio Chascomús (Buenos Aires area) on 1520 kHz had a nice signal. From North America the only noted station was a faint signal from WWZN on 1510 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
10652 2004.07.16 4 2 N08W89 0280 EAO classification was CAO
at midnight, area 0050
10653 2004.07.17     S12W89     plage
10654 2004.07.25 8 14 N08W02 0120 DSO classification was DAO
at midnight
S440 visible on
  3 S08E79 0080 CAO  
Total spot count: 12 19
SSN: 32 49

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)
2004.07 121.2 (1) 84.8 (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]