Solar Terrestrial Activity Report

Last major update issued on October 10, 2004 at 02:15 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 to unsettled on October 9. Solar wind speed ranged between 324 and 371 km/sec under the influence of a weak low speed stream from coronal hole CH117.

Solar flux measured at 20h UTC on 2.8 GHz was 88.0. 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: 31011222 (planetary), 21113331 (Boulder).

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

At midnight the visible solar disk was spotless. The solar flare activity level was low. A total of 3 C class events was recorded during the day from region 10680 at and just behind the northwest limb. This region could produce a minor M class flare today before rotating too far behind the limb. Flares: C1.2 at 04:31, C1.1 at 19:13 and C1.2 at 20:44 UTC.

Coronal mass ejections (CMEs)

October 7-9: 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 recurrent coronal hole (CH118) in the southern hemisphere was in a geoeffective position on October 8-9.

Processed SOHO/EIT 284 image at 19:06 UTC on October 9. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on October 10 and most of October 11. A coronal hole flow from coronal hole CH118 is expected to arrive on October 11 and cause unsettled to active conditions part of that day and on October 12. Quiet to unsettled is likely on October 13 becoming quiet on October 14-16.

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 to very good. Propagation along long distance north-south paths is poor to fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: WLAM Lewiston ME, however, several other stations were noted, primarily from the USA. Radio Vibración (Venezuela) was there occasionally as well. On other frequencies propagation was best towards the USA with stations as far west as Minnesota observed when I began writing this.

The local sunrise opening on October 9 was quite interesting with the best propagation towards the southeastern USA.

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
10676 2004.09.28 1   S13W67 0020 AXX spotless
10680 2004.10.08 3   N15W93 0090 CSO rotated out of view
S456 emerged on
    N16W86     plage
Total spot count: 4 0
SSN: 24 0

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 90.1 (1) 10.4 (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]