Solar Terrestrial Activity Report

Last major update issued on June 3, 2004 at 04:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update June 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update May 30, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on June 2. Solar wind speed ranged between 465 and 565 km/sec. The high speed stream from coronal hole CH98 appeared to be ending early in the day with the solar wind speed decreasing. However, the decrease in wind speed ended at about 10h UTC and wind speed was fairly stable afterwards just above 500 km/sec. It appears as if the expected high speed stream from coronal hole CH99 replaced the previous stream at this time.

Solar flux measured at 20h UTC on 2.8 GHz was 90.4. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.8).
Three hour interval K indices: 32233233 (planetary), 33334433 (Boulder).

The background x-ray flux is at the class A9 level.

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10621 developed until early afternoon at which time the region had nearly 40 spots, then the region began to decay and had lost a number of spots in the leading and intermediate section by the end of the day.
Region 10622 decayed slowly and could soon become spotless.
Region 10624 was quiet and stable.

Coronal mass ejections (CMEs)

May 31-June 2: No fully or partly 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

 A recurrent trans equatorial coronal hole (CH99) was in a geoeffective position on May 30-31.

Processed SOHO/EIT 284 image at 01:06 UTC on June 3. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on June 3-4 due to a high speed stream from coronal hole CH99. Quiet to unsettled is likely on June 5-6.

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 very poor. Propagation along long distance north-south paths is fair to good. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. Radio Vibración (Venezuela) was observed at times. Several stations from Brazil had impressive signals with the best signal noted from "1440 AM" in  Rio de Janeiro. Again the only station from North America was WWZN Boston on 1510 kHz with a very weak 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
10621 2004.05.29 19 28 S14E12 0060 DAO beta-gamma
classification was DAI
at midnight, area 0090
10622 2004.05.30 2 1 S12E32 0050 CAO classification was AXX
at midnight, area 0010.
What did SEC observe?
10623 2004.06.01 1   N08W35 0010 HRX spotless
10624 2004.06.01 1 2 S08E51 0040 HSX area was 0020
at midnight
S408 emerged on
    N13W77     plage
S409 emerged on
    S01W05     plage
Total spot count: 23 31
SSN: 63 61

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)
2003.05 115.7 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 58.1 (-1.4)
2003.11 140.8 67.3 56.7 (-1.4)
2003.12 114.9 46.5 (54.4 predicted, -2.3)
2004.01 114.1 37.2 (50.5 predicted, -3.9)
2004.02 107.0 46.0 (46.2 predicted, -4.3)
2004.03 112.0 48.9 (43.5 predicted, -2.7)
2004.04 101.2 39.3 (41.4 predicted, -2.1)
2004.05 99.8 41.5 (38.2 predicted, -3.2)
2004.06 90.2 (1) 4.6 (2) (35.3 predicted, -2.9)

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]