Solar Terrestrial Activity Report

Last major update issued on January 31, 2005 at 02:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update January 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update November 8, 2004)]
[Archived reports (last update January 29, 2005)]

Recent activity

The geomagnetic field was quiet to active on January 30. Solar wind speed ranged between 544 and 628 km/sec under the influence of a high speed stream from CH142. Wind speed decreased slowly towards the end of the day 

Solar flux measured at 20h UTC on 2.8 GHz was 85.5. The planetary A index was 16 (STAR Ap - based on the mean of three hour interval ap indices: 15.6).
Three hour interval K indices: 34343222 (planetary), 23242222 (Boulder).

The background x-ray flux is at the class A4 level.

At midnight there were 3 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 10727 developed slowly in the leading penumbra while significant decay was observed in the trailing spots. There is a weak magnetic delta structure in the leading penumbra and the region could produce C flares.
Region 10728 was quiet and stable.

Spotted regions not number by NOAA/SEC:
[S505] This region emerged in the southeast quadrant on January 30. Location at midnight: S09E28

Coronal mass ejections (CMEs)

January 28-30: No obvious fully or partly Earth directed CMEs were observed. A full halo CME observed during the evening on January 30 most likely had a backsided source.

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 coronal hole in the northern hemisphere (CH142) was in a geoeffective position on January 27-29. A fairly small recurrent coronal hole (CH143) in the southern hemisphere will likely rotate to a geoeffective position on February 2-3.

Processed SOHO/EIT 284 image at 19:06 UTC on January 30. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on January 31 and most quiet on February 1-4. A low speed stream from coronal hole CH143 could reach Earth on February 5 or 6 and cause a few unsettled and active intervals.

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 fair. Propagation along long distance north-south paths is very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: WWNN Boca Raton FL. Radio Vibración (Venezuela) was noted at times as was WLAM Lewiston ME. Above 1350 kHz propagation was at times fair to good towards the southeastern parts of the USA. The Georgia stations on 1630, 1670 and 1690 all had fair 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
10727 2005.01.24 16 9 S09W42 0110 DAI  beta-gamma-delta
classification was DAO at midnight
location S10W40
10728 2005.01.25 2 1 S13E01 0010 HSX classification was HRX at midnight
S500 visible on
    N10W86     plage
S504 emerged on
    S12W75     plage
S505 emerged on
  3 S09E28 0020 CSO  
Total spot count: 18 13  
SSN: 38 43  

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)
2003.11 140.8 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 41.7 (-2.2)
2004.07 119.1 51.0 (39.6 predicted, -1.9)
2004.08 109.6 40.9 (38.0 predicted, -1.6)
2004.09 103.1 27.7 (36.1 predicted, -1.9)
2004.10 105.9 48.4 (33.9 predicted, -2.2)
2004.11 113.2 43.7 (32.0 predicted, -1.9)
2004.12 94.5 17.9 (29.7 predicted, -2.3)
2005.01 102.8 (1) 50.4 (2) (27.0 predicted, -2.7)

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]