Solar Terrestrial Activity Report

Last major update issued on January 21, 2005 at 04:45 UTC. Last minor update posted at 19:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 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 19, 2005)]

Recent activity

The geomagnetic field was quiet to active on January 20. Solar wind speed ranged between 459 and 1000 km/sec (these values are questionable and may be invalid due to the proton storm). Other solar wind parameters indicate that the solar wind is still extremely disturbed.

Solar flux measured at 20h UTC on 2.8 GHz was 122.7. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.4).
Three hour interval K indices: 21124433 (planetary), 21123433 (Boulder).

The background x-ray flux is at the class B9 level.

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was high. A total of 5 C and 1 X class events was recorded during the day.

Region 10720 lost some area in the main penumbra, however, the region is still very complex with multiple magnetic delta structures including a very strong delta in the main penumbra. Further major flares are possible until the region rotates 1-2 days behind the northwest limb. Flares: C1.6 at 00:47, C4.8 at 03:30, long duration major X7.1/2B proton event peaking at 07:01 (associated with moderate type II and IV radio sweeps), C8.0 at 16:14, C3.6 at 18:16 and C4.5 at 21:53 UTC.
Region 10723 developed a small trailing spot and was otherwise unchanged.

Spotted regions not numbered by NOAA/SEC:
S501: This region emerged in the southeast quadrant on January 19 and developed slowly on January 20. Location at midnight: S02E38.
S502: This region emerged in the southwest quadrant on January 20 and has shown quick initial development. Location at midnight: S05W25.

Comment added at 18:54 UTC on January 21: A very strong solar wind shock was observed at SOHO at 16:48 UTC. Wind speed increased abruptly from 570 to nearly 950 km/sec. This was the arrival of the huge halo CME associated with the X7 proton flare in region 10720 at 07h on January 20. Geomagnetic storming began immediately when the CME impacted Earth with the planetary A index for the 15-18 UTC interval reaching 179 (= Kp 8 - very severe storm).

Comment added at 19:30 UTC: The interplanetary A index for the 16-19 UTC interval was 207. An exceptional northern lights display can currently be observed over large parts of North Europe. At my location huge red, green and intense blue-white colored bands can be observed, not only to the north but in the southern parts of the visible sky as well.

Coronal mass ejections (CMEs)

January 20: A full halo CME was observed after the X7 event in region 10720 at 07h UTC. While the major parts of this CME are not aimed at Earth, we could still observe a substantial impact late on January 21 or on January 22.
January 19
: A full halo CME was observed after the X1 event in region 10720 during the morning. This CME could reach Earth on January 21 as expansion speed in the direction of Earth was much slower than towards the northwest.
January 18
: No obvious fully or partly Earth directed CMEs were 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 fairly large delta shaped recurrent coronal hole (CH140) in the northern hemisphere was in a geoeffective position on January 18-20. The associated high speed stream will likely become geoeffective on  January 21.

Processed SOHO/EIT 284 image at 21:50 UTC on January 20. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to major storm on January 21-22 due to CME effects. The high speed stream from coronal hole CH140 could arrive late on January 21 and will probably cause unsettled to minor storm conditions on January 22-23.

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 to fair. Propagation along long distance north-south paths is poor to very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela), both with poor signals. Propagation was interesting on other frequencies, particularly above 1350 kHz. Quite a few stations from the USA could be heard, 1510 kHz had both WWZN Boston and WLAC Nashville at the same fair signal level, 1700 kHz had WJCC and an unidentified station playing mostly contemporary music. On 1660 kHz WWRU was the best signal, however, two other stations were audible as well.

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
10718 2005.01.07 3   S07W88 0100 CSO rotated out of view
10720 2005.01.10 27 30 N14W70 1400  EKC beta-gamma-delta
10721 2005.01.16     S03W37     plage
10722 2005.01.16     N19W51     plage
10723 2005.01.17 1 2 N06E35 0080 HSX classification was CSO at midnight
10724 2005.01.18     S12W33      
S494 emerged on

S495 visible on

S500 visible on
    N10E44     plage
S501 emerged on
  5 S02E38 0030 DSO  
S502 emerged on
  7 S05W25 0050 DAO  
Total spot count: 31 44  
SSN: 61 94  

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)
2005.01 107.5 (1) 35.4 (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]