Solar Terrestrial Activity Report

Last major update issued on October 7, 2004 at 03:45 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update August 28, 2004)]
[Archived reports (last update September 27, 2004)]

Recent activity

The geomagnetic field was quiet on October 6. Solar wind speed ranged between 289 and 333 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 92.1. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 6.3).
Three hour interval K indices: 12222222 (planetary), 03221101 (Boulder).

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

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

Region 10675 decayed slowly and quietly. The region will rotate over the southwest limb today.
Region 10676 decayed slowly and quietly.
Region 10678 redeveloped a penumbra.

A warm plage area in the southeast quadrant near the southeast limb was the source of the single flare of the day. This spotless region could continue to produce occasional C class flares as it has been doing over the last 3 days. Flare: C2.5 at 18:34 UTC.

Coronal mass ejections (CMEs)

October 4-6: No obviously Earth directed CMEs 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 trans equatorial coronal hole (CH117) was in a geoeffective position on October 3-4. A recurrent coronal hole (CH118) in the southern hemisphere could rotate to a geoeffective position on October 8-9. A southward (poorly defined) extension of the large northern polar coronal hole could reach a geoeffective position on October 7.

Processed SOHO/EIT 284 image at 19:06 UTC on October 6. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on October 7-8 due to minor effects from coronal hole CH117. Quiet is likely on October 8-10 with unsettled to active conditions possible on October 11-12 due to a coronal flow from coronal hole CH118.

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 fair to occasionally good. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay before 00:30 UTC, then WWNN Pompano Beach FL. After 01h UTC the frequency was a mess with many stations fighting for dominance. Radio Vibración (Venezuela), slightly off frequency at 1470.02 kHz, was there occasionally. On other frequencies propagation was best towards the Canadian Atlantic provinces (CJYQ 930 and VOWR 800 kHz both had impressive S9+10dB signals) and the northeast USA after 02:15 UTC, earlier the southeast USA and the Caribbean had been favored with good conditions. Tropical 1480 (Puerto Rico) had a nice S9 signal.

The local sunrise opening on October 6 was fairly good towards the southeastern USA and parts of the Caribbean, an unmonitored recording on 1590 kHz had audio disappearing as late as 07:32 UTC.

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
10675 2004.09.25 1 1 S10W76 0060 HSX classification was HAX
at midnight
10676 2004.09.28 4 2 S13W28 0030 CSO area was 0020
at midnight
10677 2004.09.28     N02W73     plage
10678 2004.10.03 4 3 N12W62 0040 CSO area was 0020
at midnight
S456 emerged on
    N16W47     plage
Total spot count: 9 6
SSN: 39 36

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)
2003.08 122.1 72.7 60.0 (-1.7)
2003.09 112.2 48.7 59.5 (-0.5)
2003.10 151.7 65.5 58.2 (-1.3)
2003.11 140.8 67.3 56.7 (-1.5)
2003.12 114.9 46.5 54.8 (-1.9)
2004.01 114.1 37.3 52.0 (-2.8)
2004.02 107.0 45.8 49.3 (-2.7)
2004.03 112.0 49.1 47.1 (-2.2)
2004.04 101.2 39.3 (44.6 predicted, -2.5)
2004.05 99.8 41.5 (40.9 predicted, -3.7)
2004.06 97.4 43.2 (38.0 predicted, -2.9)
2004.07 119.1 51.0 (36.2 predicted, -1.8)
2004.08 109.6 40.9 (34.6 predicted, -1.6)
2004.09 103.1 27.7 (32.8 predicted, -1.6)
2004.10 89.8 (1) 7.5 (2) (30.5 predicted, -2.3)

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]