Solar Terrestrial Activity Report

Last major update issued on February 7, 2005 at 05:25 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 to active on February 6. Solar wind speed ranged between 331 and 446 km/sec. A low speed stream from CH143 arrived early in the day with the interplanetary magnetic field swinging moderately southwards after 05h UTC. At 01h UTC on February 7 a high speed stream from CH144 was observed at ACE.

Solar flux measured at 20h UTC on 2.8 GHz was 97.0. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.4).
Three hour interval K indices: 22411123 (planetary), 23411223 (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 single C class event was recorded during the day.

Region 10729 decayed and could become spotless before rotating out of view at the southwest limb.
Region 10730  was quiet and stable.
New region 10731 emerged in the northeast quadrant on February 5 and was numbered the next day by SEC. The region decayed slowly on February 6.
New region 10732 rotated into view at the northeast limb on February 5 and was numbered by SEC the following day. There's lots of bright plage in this region which seemed to be developing slowly on February 6. Currently the only significant complexity is in the single trailing penumbra which has a weak magnetic delta structure. M class flares may be possible. Flare: C1.2 at 09:39 UTC.

Coronal mass ejections (CMEs)

February 4-6: 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 large recurrent coronal hole (CH144) in the northern hemisphere was in a geoeffective position on February 4-6.

Processed SOHO/EIT 284 image at 01:06 UTC on February 7. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be unsettled to minor storm on February 7-8 and quiet to active on February 9 due to a high speed stream from CH144.

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: WLAM Lewiston ME and Radio Vibración (Venezuela), both with fair signals. Otherwise there were only a few stations from North America with WWZN on 1510 kHz having 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
10729 2005.01.31 1 1 S11W66 0020 HSX classification was HRX at midnight, area 0010
10730 2005.02.04 1 1 S20E46 0050 HAX classification was HSX at midnight
10731 2005.02.06 2 1 S02E27 0030 DSO formerly region S506
classification was HSX at midnight,
area 0020
10732 2005.02.06 3 8 N09E70 0040 DAO beta-gamma-delta
formerly region S507
Total spot count: 7 11  
SSN: 47 51  

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 87.0 (1) 6.0 (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]