Solar Terrestrial Activity Report

Last major update issued on March 24, 2004 at 04:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update March 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update March 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update March 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update March 11, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on March 23. Solar wind speed ranged between 361 and 446 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 118.2. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 9.0).
Three hour interval K indices: 33222231 (planetary), 32313322 (Boulder).

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

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day.

Region 10574 decayed in some parts of the region while slow development was observed in other parts. There was less polarity intermixing than during the previous day as the positive polarity areas in the central part of the region mostly disappeared. Flare: C1.4 long duration event peaking at 07:25 UTC.
Region 10577 was quiet and stable.
Region 10578 decayed in the trailing spot section while slow development was observed in the western part of the intermediate spot section. There is a minor chance of an M class flare. Flare: C1.3 at 00:42 UTC.

Coronal mass ejections (CMEs)

March 21-23: No partly or fully earth directed CMEs observed in limited LASCO data.

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, poorly defined coronal hole (CH85) in the northern hemisphere was in a geoeffective position on March 20. A recurrent coronal hole (CH87) in the northern hemisphere will likely rotate into geoeffective positions on March 25-26.

Processed SOHO/EIT 284 image at 00:12 UTC on March 18. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on March 24 under the influence of a weak high speed stream from coronal hole CH85 and quiet to unsettled on March 25-26. A high speed stream from coronal hole CH87 could arrive on March 27 or 28 and cause unsettled to minor storm conditions.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is mostly fair, occasionally fair to good. 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 Vibración (Venezuela) and WLAM Lewiston ME. Stations from the easternmost parts of North America were heard on quite a few frequencies throughout the MW band].

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
10573 2004.03.12     S12W72     plage
10574 2004.03.16 33 26 S04W25 0130 ESC beta-gamma
classification was EAO
at midnight, area 0160
10575 2004.03.17     S18W80     plage
10577 2004.03.17 4 3 N00W01 0050 CSO area was 0070
at midnight
10578 2004.03.18 31 22 N15E05 0190 FSC beta-gamma
classification was FAO
at midnight
10579 2004.03.22 2   S13E35 0010 BXO spotless
Total spot count: 70 51
SSN: 110 81

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)
2003.02 124.5 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 60.0 (-1.8)
2003.09 112.2 48.7 (58.9 predicted, -1.1)
2003.10 151.7 65.5 (56.2 predicted, -2.7)
2003.11 140.8 67.3 (53.5 predicted, -2.7)
2003.12 114.9 46.5 (50.9 predicted, -2.6)
2004.01 114.1 37.2 (46.7 predicted, -4.2)
2004.02 107.0 46.0 (42.1 predicted, -4.6)
2004.03 107.4 (1) 49.5 (2) (39.7 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]