Solar Terrestrial Activity Report

Last major update issued on December 7, 2004 at 03:55 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 active on December 6. Solar wind speed ranged between 368 and 474 km/sec. A coronal hole related disturbance arrived near 06h UTC and caused an increase in geomagnetic activity.

Solar flux measured at 20h UTC on 2.8 GHz was 93.2. The planetary A index was 19 (STAR Ap - based on the mean of three hour interval ap indices: 18.9).
Three hour interval K indices: 13444443 (planetary), 13443433 (Boulder).

The background x-ray flux is at the class B1 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 10708 was quiet and stable.
Region 10709 developed as small patches of negative polarity flux emerged ahead of the positive polarity spots. The region currently has reversed polarities.

Coronal mass ejections (CMEs)

December 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

Recurrent trans equatorial coronal hole CH131 was in a geoeffective position on December 5.

Processed SOHO/EIT 284 image at 13:06 UTC on December 6. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on December 7. Some unsettled and active intervals are possible on December 8-9 due to effects from coronal hole CH131. Quiet conditions are likely on December 10-12.

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 to very poor. Propagation along long distance north-south paths is good to very good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Rafaela (Argentina) and Radio Cristal del Uruguay. Two unidentified stations from Argentina were noted as well. On other frequencies it was possible to hear many stations from Brazil, Argentina and Uruguay. Rádio Eldorado on 700 kHz and Rádio Bandeirantes on 840 kHz, both from São Paulo, had excellent signals at times. On 1510 kHz Radio San Carlos (Uruguay) was heard at first, later on the frequency was dominated by Radio Belgrano (Argentina). Radio Chascomús (Argentina) had a nice signal on 1520 kHz. On the antenna aimed towards the northwest none of these stations were audible, instead WWZN Boston was noted with a weak signal on 1510 while CJYQ had a nice signal on 930 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
10706 2004.11.24 1   S07W87 0060 HAX rotated out of view
10707 2004.11.24 1   S13W88 0060 HAX rotated out of view
10708 2004.11.26 1 1 N10W53 0100 HSX area was 0070
at midnight
10709 2004.12.03 4 5 N04E20 0010 BXO location was
at midnight
Total spot count: 7 6
SSN: 47 26

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)
2004.12 100.7 (1) 10.1 (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]