Solar Terrestrial Activity Report

Last major update issued on January 22, 2006 at 06:30 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 on January 21. Solar wind speed ranged between 351 and 445 (all day average 416) km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 93.8. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.1).
Three hour interval K indices: 12111001 (planetary), 13121010 (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 10848 developed further with a number of new intermediate spots emerging. C flares are likely and a minor M class flare is a possibility. Polarities are intermixed in the central area.

Spotted region not numbered by NOAA/SEC:
[S618] This region emerged on January 21 in the southeast quadrant. Location at midnight: S07E57.

Coronal mass ejections (CMEs)

January 19-21: No obviously fully or partly Earth directed CMEs were observed. No images were available for January 21 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) will likely rotate to an Earth facing position late on January 21-22. CH206 appears to have decayed quite a bit in the southern part over the last solar rotation.

Processed SOHO/EIT 284 image at 01:06 UTC on January 22. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on January 22 and become 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 fair. Propagation on long distance northeast-southwest paths is very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: WLAM Lewiston ME and Radio Vibración (Venezuela). While there were still a lot of stations from the USA and Canada around, signals were considerably weaker compared to the previous day. During the morning of January 21 propagation became excellent and North American signals were still present after 11h 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
10847 2006.01.15     S08W85     plage
10848 2006.01.18 18 28 S19W02 0200 EKI beta-gamma
classification was EAI at midnight, area 0350
S618 2006.01.21   1 S07E57 0010 AXX  
Total spot count: 18 29  
SSN: 28 49  

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 82.5 (1) 17.0 (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]