Solar Terrestrial Activity Report

Last major update issued on August 11, 2004 at 04:45 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 10. Solar wind speed ranged between 382 and 679 km/sec, first under the influence of a fairly low speed stream from coronal hole CH108, then under the influenceof a high speed stream from coronal hole CH109.

Solar flux measured at 20h UTC on 2.8 GHz was 121.4. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.9).
Three hour interval K indices: 41223433 (planetary), 41223543 (Boulder).

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

At midnight there were 5 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 10655 decayed slowly and rotated partly out of view at the southwest limb. Flare: C1.0 at 22:07 UTC.
Region 10656 developed quickly in the trailing and central parts. The central penumbra has at least one magnetic delta structure. A major flare is possible. At its current location such a flare would likely be accompanied by a significant earth directed CME. Flares: C1.1 at 06:07, C1.0 at 17:29 and C1.2 at 17:38 UTC.
Region 10657 was quiet and stable.
New region 10659 rotated into view at the northeast limb on August 8 and was finally noticed by SEC two days later.

Spotted regions not numbered by NOAA/SEC:
[S444] A new region emerged near the southeast limb on August 9.

Coronal mass ejections (CMEs)

August 9-10: No obviously Earth directed CMEs were detected in LASCO images.
August 8: A bright full halo CME was observed in LASCO C3 images starting at 09:42 UTC. The leading front was first observed off of the east limb and the south pole. The source of this event was likely about 5-6 days behind the southeast limb, probably in old region 10652.

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 (CH108) in the southern hemisphere was in a geoeffective position on August 7. The southernmost part of a large, poorly defined coronal hole (CH109) in the northern hemisphere was in a geoeffective position on August 8-9.

Processed SOHO/EIT 284 image at 01:06 UTC on August 11. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on August 11-12 due to a high speed stream from coronal hole CH109, quiet to unsettled is likely on August 13.

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 poor to fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay early in the night, Radio Vibración (Venezuela) before, at and after local sunrise. Near local sunrise a number of stations from Venezuela were heard throughout the MW band with the best signals noted on 970, 1140, 1420, 1500, 1520 and 1590 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
10655 2004.07.30 4 2 S10W83 0100 CAO  
10656 2004.08.06 43 74 S12E18 0700 EKC beta-gamma-delta
area was 0850
at midnight
10657 2004.08.06 1 1 N11E25 0030 HSX  
10658 2004.08.07     S05E12     plage
10659 2004.08.10 5 3 N17E59 0030 CRO formerly region S443
classification was CAO
at midnight
S441 emerged on
    N16W78     plage
S444 emerged on
  2 S10E46 0010 BXO  
Total spot count: 53 82
SSN: 93 132

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 95.5 (1) 20.1 (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]