Solar Terrestrial Activity Report

Last major update issued on April 3, 2004 at 03:25 UTC. Minor update posted at 16:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update April 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update March 28, 2004)]

Recent activity

The geomagnetic field was very quiet to quiet on April 2. Solar wind speed ranged between 348 and 428 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 108.1. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.4).
Three hour interval K indices: 10011211 (planetary), 21112211 (Boulder).

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

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

Region 10581 was quiet and stable.
Region 10582 decayed slowly and quietly.
Region 10587 was mostly unchanged and quiet.
Region 10588 developed slowly and was quiet.

Comment added at 16:55 UTC on April 3: A fairly weak solar wind shock was observed at SOHO at 08:49 UTC. While the interplanetary magnetic field initially did not hint at a strong disturbance, the geomagnetic storm has recently intensified to the minor to major storm level.

Coronal mass ejections (CMEs)

March 31: A very long duration C3.4 event in region 10582 near noon on March 31 was associated with an earth directed CME. LASCO images late in the day revealed a full halo CME.

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

An elongated, recurrent trans equatorial coronal hole (CH88) will be in a geoeffective position on April 1-7. This coronal hole has extended westwards and will be influencing the geomagnetic field for at least a week.

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 unsettled early on April 3. Sometime on April 3 the CME observed on March 31 is likely to reach Earth and could cause unsettled to minor storm conditions. On April 4-10 a high speed stream from coronal hole CH88 will be dominating the solar wind and cause unsettled to minor storm conditions early in the interval becoming quiet to active later on.

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 currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). Quite a few stations from Venezuela were noted on other frequencies 01-02:30 UTC, as were most of the usual Newfoundland stations. Then the interplanetary magnetic field became stronger southwards oriented and propagation to northern South America and eastern North America became much worse, instead some stations from Brazil were noted].

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
10581 2004.03.24 2 1 S05W41 0100 HSX  
10582 2004.03.25 15 4 N14W35 0140 ESO classification was DSO
at midnight
10584 2004.03.27     S13W55     plage
10585 2004.03.27 1   S15W27 0010 AXX spotless
10587 2004.03.28 30 21 S13E11 0160 EAO  
10588 2004.04.01 1 3 S12E64 0060 HSX classification was CSO
at midnight
Total spot count: 49 29
SSN: 99 69

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)
2003.03 131.4 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 59.5 (-0.5)
2003.10 151.7 65.5 (58.0 predicted, -1.5)
2003.11 140.8 67.3 (55.9 predicted, -2.1)
2003.12 114.9 46.5 (53.3 predicted, -2.6)
2004.01 114.1 37.2 (49.1 predicted, -4.2)
2004.02 107.0 46.0 (44.5 predicted, -4.6)
2004.03 112.0 48.9 (41.7 predicted, -2.8)
2004.04 110.5 (1) 6.6 (2) (39.6 predicted, -2.1)

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 some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.

[DX-Listeners' Club]