Solar Terrestrial Activity Report

Last major update issued on June 4, 2004 at 04:45 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 4. Solar wind speed ranged between 426 and 505 km/sec under the slowly decreasing influence of a weak high speed stream from coronal hole CH99.

Solar flux measured at 20h UTC on 2.8 GHz was 89.4. 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: 33233323 (planetary), 33233223 (Boulder).

The background x-ray flux is at the class A8 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 10621 decayed slowly with several spots disappearing and the trailing penumbra losing most of its area.
Region 10624 decayed slowly and could soon become spotless.

Spotted regions not numbered by NOAA/SEC:
[S411] This region emerged in the northeast quadrant near the central meridian on June 4. Location at midnight: N06E07.
[S412] A new region emerged in the southeast quadrant on June 4. Location at midnight: S08E43.

Coronal mass ejections (CMEs)

June 2-4: No fully or partly Earth directed CMEs observed. A large full halo CME was observed during the morning of June 4, its source was a few days behind the west limb.

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. A small recurrent coronal hole (CH100) in the northern hemisphere was in a geoeffective position on June 4.

Processed SOHO/EIT 284 image at 01:05 UTC on June 5. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled is on June 5-7 with only a minor increase in activity on June 8 as a low speed stream from coronal hole CH100 arrives.

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 excellent. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela). At and after local sunrise excellent propagation towards Brazil and Uruguay were noted. Rádio Sociedade on 740 kHz had a near local like signal and Brazil was observed on unusual frequencies like 580, 590, 610, 720 (at the same level as co-channel Europeans), 780, 790, 800, 850, 870, 880, 890, 920 kHz and so on. There was still weak audio and strong carriers on several frequencies over 2 hours after local sunrise (which was at 02:35 UTC). Radio Internacional (Uruguay) on 1480 kHz was noted with a nice signal after local sunrise. All in all one of the best sunrise openings I've ever noted towards the southeastern and eastern parts of South America.

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 21 10 S14W15 0050 CSI classification was CSO
at midnight, area 0030
10622 2004.05.30     S09E07     plage
10623 2004.06.01     N08W61     plage
10624 2004.06.01 2 2 S08E24 0010 AXX  
10625 2004.06.03 2   S12W69 0020 AXX spotless
S409 emerged on
    S01W31     plage
S411 emerged on
  4 N06E07 0010 BXO  
S412 emerged on
  3 S08E43 0020 CSO  
Total spot count: 25 19
SSN: 55 59

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 90.0 (1) 9.0 (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]