Solar Terrestrial Activity Report

Last major update issued on February 20, 2005 at 05:35 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 February 1, 2005)]
[Archived reports (last update February 16, 2005)]

Recent activity

The geomagnetic field was quiet to active on February 19. Solar wind speed ranged between 468 and 636 km/sec. A solar wind disturbance arrived at SOHO at about 05:30 and was associated with a sudden increase in wind density and temperature. This was likely the arrival of the CME observed after a C4 event in region 10734 on February 16.

Solar flux measured at 20h UTC on 2.8 GHz was 98.5. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.0).
Three hour interval K indices: 12344332 (planetary), 12343333 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 1 C and 1 M class events was recorded during the day.

Region 10732 continued to be active from behind the northwest limb. Flares: C1.2 at 06:09 and M3.3 at 11:01 UTC.
Region 10733 was quiet and stable and will soon rotate over the southwest limb.
Region 10734 decayed further and could become spotless today.
Region 10735 redeveloped a penumbra to the southeast of the large penumbra. Otherwise the region was mostly unchanged.

Coronal mass ejections (CMEs)

February 17: A full halo CME was observed early in the day and was likely associated with the C4.9 flare in region 10734 at 23:38 on February 16.
February 18-19:
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 small coronal hole (CH147) in the northern hemisphere will likely rotate to a geoeffective position on February 19-20. A recurrent coronal hole (CH148) in the northern hemisphere will likely rotate to a geoeffective position on February 23-24.

Processed SOHO/EIT 284 image at 01:06 UTC on February 20. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on February 20 becoming quiet to unsettled on February 21. For February 22-23 a low speed stream from CH147 could cause some 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. Propagation along long distance north-south paths is fair to poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela) with a fair to good signal. On other frequencies several stations from North America were audible. WWZN on 1510 kHz had a fair signal while both WCNZ and WWRU were heard on 1660 kHz with poor to 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
10733 2005.02.07 2 1 S08W80 0070 CSO classification was HSX at midnight, area 0050
10734 2005.02.09 1 1 S05W63 0040 HSX classification was HRX at midnight, area 0010
10735 2005.02.10 18 7 S09W45 0410 DKI beta-gamma
classification was DKO at midnight, area 0340
S511 emerged on
    S06W71     plage
S513 emerged on
  S04W49     plage
S514 emerged on
    S08E04     plage
S515 emerged on
    S13E22     plage
S516 emerged on
    S07W09     plage
S517 emerged on
    N14W35     plage
Total spot count: 21 9  
SSN: 51 39  

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)
2003.12 114.9 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 40.3 (-1.4)
2004.08 109.6 40.9 (38.9 predicted, -1.4)
2004.09 103.1 27.7 (36.6 predicted, -2.3)
2004.10 105.9 48.4 (34.4 predicted, -2.2)
2004.11 113.2 43.7 (32.5 predicted, -1.9)
2004.12 94.5 17.9 (30.2 predicted, -2.3)
2005.01 102.2 31.3 (27.6 predicted, -2.6)
2005.02 103.6 (1) 38.1 (2) (25.2 predicted, -2.4)

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]