Solar Terrestrial Activity Report

Last major update issued on December 31, 2006 at 05:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update November 12, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update November 12, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update November 12, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update December 18, 2006)]

Recent activity

The geomagnetic field was very quiet on December 30. Solar wind speed ranged between 332 and 363 km/s (all day average 345 km/s - unchanged from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 80.0. The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.6). Three hour interval K indices: 10000000 (planetary), 00001200 (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.

Coronal mass ejections (CMEs)

December 28-30: No obvious partly or fully Earth directed CMEs were detected in LASCO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent coronal hole (CH254) in the southern hemisphere was in an Earth facing position on December 30-31.

Processed SOHO/EIT 195 image at 04:36 UTC on December 31. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet on December 31 - January 1. A high speed wind from CH254 will likely cause unsettled to minor storm conditions on January 2-3.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)



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) Effects from a CME are likely to be observed at 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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is very poor.

Monitoring remarks from a location near N58E06: Relatively few stations from North America were heard during the night, none had better than a fair signal.

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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10931 2006.12.25     S07W12     plage
10932 2006.12.25     S08W31     plage
10933 2006.12.30 1 3 S04E78 0060 AXX classification was DSO at midnight, area 0100, location S05E75
S686 2006.12.30   3 N03E74 0050 HAX  
Total spot count: 1 6  
SSN: 11 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)
2005.09 91.1 21.9 25.8 (-1.6)
2005.10 77.0 8.7 25.5 (-0.3)
2005.11 86.3 18.0 24.9 (-0.6)
2005.12 90.7 41.1 23.0 (-1.9)
2006.01 83.4 15.3 20.8 (-2.2)
2006.02 76.5 4.9 18.6 (-2.2)
2006.03 75.4 10.6 17.3 (-1.3)
2006.04 89.0 30.2 17.1 (-0.2)
2006.05 80.9 22.2 17.3 (+0.2)
2006.06 76.5 13.9 (16.3 predicted, -1.0)
2006.07 75.7 12.2 (14.7 predicted, -1.6)
2006.08 79.0 12.9 (14.2 predicted, -0.5)
2006.09 77.8 14.5 (14.1 predicted, -0.1)
2006.10 74.3 10.4 (13.0 predicted, -1.1)
2006.11 86.3 21.5 (11.5 predicted, -1.5)
2006.12 84.5 (1) 21.3 (2) (11.3 predicted, -0.2)

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% lower.

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.


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