Solar Terrestrial Activity Report

Last major update issued on February 24, 2004 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 February 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update February 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update February 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update February 18, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on February 23. Solar wind speed ranged between 396 and 458 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 104.3. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5).
Three hour interval K indices: 21223332 (planetary), 23223332 (Boulder).

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

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was very low. No C class events was recorded during the day. 

Region 10563 was quiet and stable.
Region 10564 developed in the intermediate spot section while several small spots disappeared, particularly in the trailing spot section. The region is not as complex as one day ago with less polarity intermixing observed. There is still a chance of a minor M class flare.
New region 10565 emerged in the southeast quadrant on February 22 and was numbered the next day by SEC. The region developed on February 23. While several spots emerged and penumbral area increased, the region has a simple magnetic layout.

Spotted regions not numbered by NOAA/SEC:
[S363] This region emerged early on February 23 to the north of region 10565. Location at midnight: N05E32.

Coronal mass ejections (CMEs)

February 21-23: No partly or fully earth directed CMEs 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

The southernmost parts of a coronal hole (CH82) in the northern hemisphere will rotate into geoeffective positions on February 22-23. A coronal hole (CH83) is currently rotating into view at the east limb.

Processed SOHO/EIT 284 image at 01:06 UTC on February 24. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on February 24. On February 25-26 a high speed from coronal hole CH82 could arrive and may cause unsettled to active conditions.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is fair. Propagation along long distance north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela). Several stations from the eastern parts of North America could be heard on other frequencies, however, the usual Newfoundland and Nova Scotia stations were weaker than one day ago. Instead some Caribbean stations had better signals].

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.

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
10560 2004.02.15     S17W74     plage
10561 2004.02.15     N02W43     plage
10562 2004.02.19 1   S13E13 0000 AXX spotless
10563 2004.02.20 1 1 S24E26 0010 HRX classification was HSX
at midnight, area 0030
strange SEC data
10564 2004.02.21 20 22 N13E13 0300 EKO beta-gamma
classification was DKO
at midnight, area 0480
longitudinal extent: 9
10565 2004.02.23 6 17 S05E35 0050 DRO formerly region S362
classification was DAO
at midnight, area 0100
S358 emerged on
    S06W27     plage
S359 emerged on
    S14W25     plage
S363 emerged on
  2 N05E32 0020 DRO  
Total spot count: 28 43
SSN: 68 83

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)
2003.01 144.0 79.7 80.8 (-1.2)
2003.02 124.5 46.0 78.3 (-2.5)
2003.03 131.4 61.1 74.0 (-4.3)
2003.04 126.4 60.0 70.1 (-3.9)
2003.05 115.7 55.2 67.6 (-2.5)
2003.06 129.3 77.4 65.0 (-2.6)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 (59.4 predicted, -2.4)
2003.09 112.2 48.7 (57.6 predicted, -1.8)
2003.10 151.7 65.5 (54.9 predicted, -2.7)
2003.11 140.8 67.3 (52.2 predicted, -2.7)
2003.12 114.9 46.5 (49.6 predicted, -2.6)
2004.01 114.1 37.2 (45.4 predicted, -4.2)
2004.02 104.8 (1) 55.8 (2) (40.8 predicted, -4.6)

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 sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.

[DX-Listeners' Club]