Solar Terrestrial Activity Report

Last major update issued on March 21, 2005 at 04:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update March 3, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update March 3, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update March 3, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update March 16, 2005)]

Recent activity

The geomagnetic field was quiet on March 20. Solar wind speed ranged between 331 and 441 km/sec, steadily decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 89.0. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.1).
Three hour interval K indices: 12122111 (planetary), 13122231 (Boulder).

The background x-ray flux is at the class A8 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 3 C class events was recorded during the day. Region 10742 behind the southwest limb produced a C4.1 flare at 01:59 UTC.

Region 10743 decayed losing both spots and penumbral area. Flares: C1.2 at 06:14 and C2.1 at 11:52 UTC.
New region 10744 emerged in the southeast quadrant on March 19 and was numbered the next day by SEC. The region added some penumbral area on March 20, however, the separation between the opposite polarity areas increased. Unless new flux emerges the region is likely to decay.

Coronal mass ejections (CMEs)

March 18-20: 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 recurrent trans equatorial coronal hole (CH153) will rotate to a geoeffective position on March 21-23, the westernmost part is only in the northern hemisphere and poorly defined.

Processed SOHO/EIT 284 image at 13:06 UTC on March 11. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be mostly quiet on March 21-23 becoming quiet to unsettled on March 24 due to effects from CH153. Quiet to active conditions are likely on March 25-26 as the coronal hole effects increase.

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 to occasionally good. Propagation along long distance north-south paths is very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) before 03h UTC with a fair signal, then, gradually, WWNN Boca Raton FL and WLAM Lewiston ME took over dominance. Propagation towards North America is improving and several stations had fair to good signals. Surprisingly CJYQ on 930 kHz was poor and allowed Radio Surco (Cuba) to dominate the frequency.

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
10743 2005.03.09 12 5 S08W70 0310 DAO classification was DSO at midnight, area 0200
10744 2005.03.20 7 13 S12E01 0060 DSO formerly region S526
classification was DAO at midnight, area 0090
S524 visible on
    N16W66     plage
S525 emerged on
    S13W45     plage
Total spot count: 19 18  
SSN: 39 38  

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)
2004.01 114.1 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 39.2 (-1.1)
2004.09 103.1 27.7 (37.4 predicted, -1.8)
2004.10 105.9 48.4 (35.2 predicted, -2.2)
2004.11 113.2 43.7 (33.3 predicted, -1.9)
2004.12 94.5 17.9 (31.0 predicted, -2.3)
2005.01 102.2 31.3 (28.3 predicted, -2.7)
2005.02 97.2 29.1 (25.9 predicted, -2.4)
2005.03 94.2 (1) 27.5 (2) (24.1 predicted, -1.8)

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]