Solar Terrestrial Activity Report

Last major update issued on February 15, 2005 at 04:35 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 1, 2005)]

Recent activity

The geomagnetic field was quiet on February 14. Solar wind speed ranged between 346 and 441 km/sec. A low speed stream from coronal hole CH146 arrived at ACE at 05:10 UTC. Solar wind speed increased from 360 km/sec to an average of 390 km/sec. While the arrival of this disturbance was hardly noticeable geomagnetically, radio wave propagation favored more southerly paths compared to the previous day.

Solar flux measured at 20h UTC on 2.8 GHz was 118.1. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.0).
Three hour interval K indices: 02111122 (planetary), 12112122 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day.

Region 10733 changed with the single penumbra splitting into two smaller penumbrae. Flare: C1.5 at 11:58 UTC. The event was associated with a moderate type II radio sweep.
Region 10734 added a few small spots. Flare: C1.9 at 04:08 UTC. This event was associated with a moderate type IV radio sweep.
Region 10735 developed slowly and appears to have the largest flare potential of all regions on the disk. A minor M class flare is possible. A magnetic delta structure could be developing in a small penumbra to the southeast of the largest penumbra.

Spotted regions not numbered by NOAA/SEC:
[S512] This region emerged on February 14 in the southwest quadrant. Location at midnight: S04W44.

Coronal mass ejections (CMEs)

February 13: A CME observed after a C2.7 flare in region 10733 at 10:47 UTC could have geoeffective components.
February 12 and 14:
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 coronal hole (CH145) in the northern hemisphere will likely rotate to a geoeffective position on February 13-15. A small coronal hole (CH146) in the southern hemisphere was in a potentially geoeffective position on February 11.

Processed SOHO/EIT 284 image at 01:06 UTC on February 15. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on February 15 due to a low speed stream from CH146. A high speed stream from CH145 could arrive on February 16 and cause unsettled conditions that day and unsettled to minor storm conditions on February 17-18.

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 poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay before 03 UTC. At 04 UTC WWNN Boca Raton FL had the best signal. The only other signal from North America observed at that time was from WJCC Miami Springs FL on 1700 kHz..

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
10730 2005.02.04 3   S19W57 0010 BXO spotless
10731 2005.02.06     S02W77     plage
10732 2005.02.06 7   N12W43 0010 BXO spotless
10733 2005.02.07 22 8 S09W13 0230 CAO SEC spot count a typo?
10734 2005.02.09 7 6 S05E04 0070 CAO classification was
CSO at midnight
10735 2005.02.10 26 21 S08E20 0440 DKO beta-gamma
S509 emerged on
    S07W57     plage
S511 emerged on
    S06W06     plage
S512 emerged on
  2 S04W44 0010 BXO  
Total spot count: 65 37  
SSN: 115 77  

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)
2005.02 101.5 (1) 28.2 (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]