Solar Terrestrial Activity Report

Last major update issued on February 1, 2005 at 01:55 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 minor storm on January 31. Solar wind speed ranged between 478 and 775 km/sec under the influence of a high speed stream from CH142. A fairly quick increase in wind speed was observed 08-10h UTC. Solar wind temperature increased significantly as well.

Solar flux measured at 20h UTC on 2.8 GHz was 86.2. The planetary A index was 19 (STAR Ap - based on the mean of three hour interval ap indices: 19.4).
Three hour interval K indices: 32345431 (planetary), 42344431 (Boulder).

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

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was low. A single C class event was recorded during the day.

Region 10727 decayed further and was quiet.
New region 10729 emerged on January 30 in the southeast quadrant and was numbered the next day by SEC. The region developed very quickly early in the day. Later on the opposite polarity areas drifted apart, the region stopped developing and flare activity ceased. Flare: C1.3 at 10:52 UTC.

Coronal mass ejections (CMEs)

January 29-31: No obvious fully or partly Earth directed CMEs were observed. A full halo CME observed during the afternoon and early 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 31. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on February 1 and inactive to quiet on February 2-4. 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 poor to occasionally 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: WLAM Lewiston ME. A number of stations from the Canadian Atlantic provinces and the easternmost parts of the USA were noted on other frequencies, WWZN on 1510 kHz had the best 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
Location at midnight Area Classification Comment
10727 2005.01.24 7 3 S09W53 0110 DAO area was 0080 at midnight
10728 2005.01.25 1   S11W12 0000 AXX spotless
10729 2005.01.31 11 10 S10E18 0070 DSI formerly region S505
classification was DSO at midnight
location: S10E16
S504 emerged on
    S12W88     plage
Total spot count: 19 13  
SSN: 49 33  

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)
2005.01 102.2 (1) 52.0 (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]