Solar Terrestrial Activity Report

Last major update issued on December 11, 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 December 3, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update December 3, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update December 3, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update November 8, 2004)]
[Archived reports (last update December 1, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on December 10. Solar wind speed ranged between 358 and 460 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 84.8. The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.5).
Three hour interval K indices: 12233233 (planetary), 12233223 (Boulder).

The background x-ray flux is at the class A5 level.

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

Region 10709 again lost the spot in the leading polarity area and had a single small spot emerge in the trailing negative polarity area.
New region 10711 emerged in the northwest quadrant on December 9 and was numbered the next day by SEC. The region developed slowly on December 10.

Coronal mass ejections (CMEs)

December 8: A full halo (asymmetrical) CME was observed in LASCO C2 images prior to a 24 hour period where no high speed telemetry from SOHO was available. This CME is likely to impact Earth on December 11.
December 9-10:
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

Coronal hole CH132 in the southern hemisphere may have been in a geoeffective position on December 9-10. An extension (CH133) of the northern polar coronal hole could reach a geoeffective position on December 13.

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


The geomagnetic field is expected to be quiet to minor storm on December 11-12 due to CME expected to arrive during the latter half of Dec.11. Effects from coronal hole CH132 could reach Earth on  December 12 and cause unsettled to active conditions that day and on Dec. 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 fair to good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay and Radio Rafaela. There was an unidentified Argentinean as well. Occasionally WWNN (Pompano Beach FL) was heard. On other frequencies propagation was best towards the southeastern part of Brazil and the Buenos Aires area in Argentina. Rádio Jovem Pan in São Paulo was noted on 620 kHz. From North America most of the Newfoundland stations below 1000 kHz had poor to fair signals.

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
10709 2004.12.03 1 1 N05W38 0010 AXX location was N07W27
at midnight
10710 2004.12.08 4   S08E22 0010 BXO spotless
10711 2004.12.10 4 4 N13W20 0020 DSO formerly region S487
area was 0030
at midnight
Total spot count: 9 5
SSN: 39 25

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)
2003.10 151.7 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 45.5 (-1.6)
2004.05 99.8 41.5 43.9 (-1.6)
2004.06 97.4 43.2 (42.2 predicted, -1.7)
2004.07 119.1 51.0 (40.6 predicted, -1.6)
2004.08 109.6 40.9 (39.0 predicted, -1.6)
2004.09 103.1 27.7 (37.1 predicted, -1.9)
2004.10 105.9 48.4 (34.9 predicted, -2.2)
2004.11 113.2 43.7 (33.0 predicted, -1.9)
2004.12 94.6 (1) 14.8 (2) (30.7 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]