Solar Terrestrial Activity Report

Last major update issued on January 23, 2006 at 04:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 8, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 8, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update January 8, 2006)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update January 8, 2006)]

Recent activity

The geomagnetic field was quiet to unsettled on January 22. Solar wind speed ranged between 347 and 381 (all day average 356) km/sec. A high speed stream from CH206 arrived early on January 23.

Solar flux measured at 20h UTC on 2.8 GHz was 92.8. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.5).
Three hour interval K indices: 11123302 (planetary), 02233321 (Boulder).

The background x-ray flux is at the class A7 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 5 C class events was recorded during the day.

Region 10848 developed further early in the day. Slow decay was observed during the latter half of the day, particularly in the intermediate spot section where several spots disappeared. The intermixing observed in the central part had decreased significantly. Further C class flares are possible. Should new flux emerge the region will again become capable of producing minor M class flares. Flares: C1.3 at 12:43, C4.1 at 14:10, C2.0 at 16:57, C1.7 at 21:25 and C1.8 at 21:50 UTC.
New region 10849 emerged in the southeast quadrant on January 21 and was numbered the next day by SEC.

Spotted region not numbered by NOAA/SEC:
[S619] This region emerged on January 22 in the northeast quadrant. Location at midnight: N06E08.

Coronal mass ejections (CMEs)

January 20-22: No obviously fully or partly Earth directed CMEs were observed. No images were available for January 21-22 when I wrote this.

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 recurrent trans equatorial coronal hole (CH206) was in an Earth facing position on January 21-23. CH206 has decayed in the southern part over the last solar rotation.

Processed SOHO/EIT 284 image at 19:06 UTC on January 22. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be unsettled to active on January 23-24 due to effects from CH206. Quiet to unsettled is likely on January 25-26.

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) 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.


Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor to fair. Propagation on long distance northeast-southwest paths is very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). Several stations from the easternmost parts of North America were still audible, however, propagation to locations further south was improved. In particular stations from Venezuela and Cuba had fair to good 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
10848 2006.01.18 39 29 S19W15 0250 EAC beta-gamma
classification was EAI at midnight
10849 2006.01.22 1 2 S07E44 0010 HSX formerly region S618
S619 2006.01.22   1 N06E08 0000 AXX  
Total spot count: 40 32  
SSN: 60 62  

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)
2004.11 113.2 43.5 35.3 (-0.6)
2004.12 94.5 17.9 35.2 (-0.1)
2005.01 102.2 31.3 34.6 (-0.6)
2005.02 97.2 29.2 33.9 (-0.7)
2005.03 89.9 24.5 33.5 (-0.4)
2005.04 86.0 24.4 31.6 (-1.9)
2005.05 99.3 42.6 28.9 (-2.7)
2005.06 93.7 39.6 28.8 (-0.1)
2005.07 96.4 39.9 (29.1 predicted, +0.3)
2005.08 90.5 36.4 (27.4 predicted, -1.7)
2005.09 91.1 22.1 (25.4 predicted, -2.0)
2005.10 77.0 8.5 (23.4 predicted, -2.0)
2005.11 86.3 18.0 (21.0 predicted, -2.4)
2005.12 90.7 41.2 (18.2 predicted, -2.8)
2006.01 83.0 (1) 18.9 (2) (15.2 predicted, -3.0)

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.

[DX-Listeners' Club]