Solar Terrestrial Activity Report

Last major update issued on December 30, 2004 at 14:35 UTC. Posted late due to no Internet connection.

[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 24, 2004)]

Recent activity

The geomagnetic field was quiet to active on December 29. Solar wind speed ranged between 411 and 480 km/sec, most of the day under the influence of what is likely a coronal hole flow.

Solar flux measured at 20h UTC on 2.8 GHz was 98.5. The planetary A index was 18 (STAR Ap - based on the mean of three hour interval ap indices: 18.4).
Three hour interval K indices: 44344222 (planetary), 34344332 (Boulder).

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

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was moderate. A total of 5 C and 2 M class events were recorded during the day.

Region 10713 rotated out of view at the southwest limb. Flares: C1.3 at 02:22, C7.5 at 03:00, C4.9 at 05:53, C2.6 long duration event peaking at 08:24, C2.5 at 13:38 and M1.4 at 19:20 UTC.
Region 10715 developed slowly and remains a complex region capable of producing M class flares. rThere is a fairly strong magnetic delta in the central northern part of the main penumbra. Flare: M2.3 at 16:27 UTC with an associated CME observed over the east limb.

Coronal mass ejections (CMEs)

December 29: The CME associated with the M2.3 flare in region 10715 was well defined over the east limb, very faint extensions were observed around the remainder of the disk.
December 27-28:
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 poorly defined extension (CH137) of a coronal hole in the northern hemisphere was in a geoeffective position on December 29. Recurrent trans equatorial coronal hole CH136 will rotate into a geoeffective position on December 31-January 1.

Processed SOHO/EIT 284 image at 18:57 UTC on December 29. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on December 30 - January 2.

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. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: none, weak signals  were noted from a number of stations: Radio Cristal del Uruguay, Radio Vibración, WWNN and WLAM. Propagation was best above 1400 kHz with the most interesting station being an unidentified NewsTalk station on 1650 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
10713 2004.12.17 4   S09W91 0150 EAI rotated out of view
SEC classification
and area not supported
by any available images
10715 2004.12.28 3 8 N04E61 0260 DKO beta-delta
classification was DKC
at midnight, area 0410
S491 emerged on
    S16W24     plage
Total spot count: 7 8
SSN: 27 18

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 94.2 (1) 31.9 (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]