Solar Terrestrial Activity Report

Last major update issued on February 1, 2004 at 04:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 4, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 4, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update January 4, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update January 27, 2004)]

Recent activity

The geomagnetic field was quiet to minor storm on January 31. Solar wind speed ranged between 430 and 684 km/sec under the influence of high speed streams from coronal holes CH78 and CH79.

Solar flux measured at 20h UTC on 2.8 GHz was 94.4. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 11.4).
Three hour interval K indices: 21353121 (planetary), 12343221 (Boulder).

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

At midnight there were 5 spotted regions on the visible disk. Solar flare activity was low. A total of 1 C class event was recorded during the day.

Region 10546 developed several small leading spots, however, the region remains simply structured.
Region 10547 developed slowly and quietly. New spots have formed in the leading negative polarity field early on February 1 and the chance of a C class flare is increasing.
New region 10548 emerged in the northeast quadrant on January 30 and was numbered the next day by SEC. The region decayed slightly on January 31.
New region 10549 rotated fully into view at the northeast limb. The region changed quite a bit during the day with new spots emerging in both the leading and trailing spot section while other spots disappeared. There is a small patch of negative polarity at the southeastern edge of the leading positive polarity field. Further C class flaring is likely. Flare: C4.1 at 06:22 UTC.

Spotted regions not numbered by NOAA/SEC:
[S343] This region emerged due north of region 10548 on January 31. Location at midnight: N15E30.

Coronal mass ejections (CMEs)

January 29-31: No partly or fully earth directed CME 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 (CH78) in the northern hemisphere will rotate into a geoeffective position on January 28 - February 2. Another coronal hole (CH79) in the southern hemisphere is the southern part of what was coronal hole CH74 during the previous rotation.

Processed SOHO/EIT 284 image at 01:06 UTC on February 1. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to minor storm February 1-5 under the influence of high speed streams from coronal holes CH78 and CH79.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along long distance north-south paths is poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Rafaela (Argentina)]

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
10545 2004.01.29     S20W45     plage
10546 2004.01.29 1 7 S12E41 0040 HSX classification was CSO
at midnight
10547 2004.01.30 4 12 S10E01 0020 DSO classification was CAO
at midnight, area 0040
10548 2004.01.31 1 3 N06E30 0010 HSX formerly region S341
classification was BXO
at midnight
10549 2004.01.31 3 10 N13E70 0090 DSO formerly region S342
classification was DAO
at midnight
S336 emerged on
    N12W57     plage
S337 emerged on
    S04W21     plage
S338 emerged on
    N16W34     plage
S343 emerged on
  4 N15E30 0020 CSO  
Total spot count: 9 36
SSN: 49 86

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)
2002.12 157.2 80.8 82.0 (-3.2)
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 (62.0 predicted, -3.0)
2003.08 122.1 72.7 (59.4 predicted, -2.6)
2003.09 112.2 48.7 (57.5 predicted, -1.9)
2003.10 151.7 65.6 (54.7 predicted, -2.8)
2003.11 140.8 67.2 (52.0 predicted, -2.7)
2003.12 114.9 47.0 (49.4 predicted, -2.6)
2004.01 114.1 (1) 61.4 (2) (45.3 predicted, -4.1)

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]