Solar Terrestrial Activity Report

Last major update issued on December 9, 2004 at 04:55 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 unsettled on December 8. Solar wind speed ranged between 413 and 511 km/sec under the influence of a coronal hole flow.

Solar flux measured at 18h UTC on 2.8 GHz was 80.9 (the measurement at 20h UTC was enhanced because of a long duration event). The planetary A index was 10 (STAR Ap - based on themean of three hour interval ap indices: 9.6).
Three hour interval K indices: 32322232 (planetary), 32422232 (Boulder).

The background x-ray flux is at the class A8 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day.

Region 10708 was quiet and stable and is rotating over the northwest limb.
Region 10709 lost all spots in the leading positive polarity field. Flare: long duration C2.5 event peaking at 19:59 UTC. This event was associated with a weak type II radio sweep and a large filament eruption spanning about 20 degrees longitude across the central meridian.
New region 10710 emerged early in the day in a hot plage area near the southeast limb. Flare: C1.0 at 04:14 UTC.

Coronal mass ejections (CMEs)

December 8: With only a few LASCO images available for the time after the LDE in region 10709, it is hard to tell how large and fast the associated CME was. Still it is likely that a CME will reach Earth on December 11 and cause unsettled to minor storm conditions.
December 6-7:
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 small coronal hole in the southern hemisphere could rotate into a geoeffective position on December 9-10.

Processed SOHO/EIT 284 image at 19:06 UTC on December 8. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on December 9, quiet on December 10 and quiet to minor storm on December 11-12

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. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración. On other frequencies propagation was best towards Brazil before 02h UTC and best towards the easternmost part of North America after 04h 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
10708 2004.11.26 1 1 N09W81 0080 HAX classification was HSX
at midnight
10709 2004.12.03 7 4 N04W11 0020 BXO classification was AXX
at midnight, area 0000
location: N08E00
10710 2004.12.08 2 1 S08E47 0020 AXX areas was 0010
at midnight
location: S07E45
Total spot count: 10 6
SSN: 40 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)
2003.10 151.7 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 96.8 (1) 12.3 (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]