Solar Terrestrial Activity Report

Last major update issued on May 9, 2004 at 04:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 3, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 3, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update May 3, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update May 8, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on May 8. Solar wind speed ranged between 444 and 502 km/sec under the weakening influence of a high speed stream from coronal hole CH94.

Solar flux measured at 20h UTC on 2.8 GHz was 87.2. The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.6).
Three hour interval K indices: 33223332 (planetary), 33132222 (Boulder).

The background x-ray flux is at the class B1 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 10605 decayed further in the leading penumbra, however, new spots emerged just east of that penumbra.
Region 10606 was quiet. The region is somewhat interesting as there is not much separation between the positive and negative polarity fields, the single penumbra has negative polarity spots and has positive polarity areas on all sides except in the south.

Spotted regions not numbered by NOAA/SEC:
[S400] This region emerged in the southeast quadrant on May 7 and was stable on May 8 with a few tiny spots. Location at midnight: S11E13.

Coronal mass ejections (CMEs)

May 6 and 8: No fully or partly Earth directed CME observed.
May 7: A faint halo CME was observed in LASCO images after 15h UTC. This CME may have been associated with a C1 event in region 10605.

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 coronal hole in the northern hemisphere is probably located too far to the north to become geoeffective.

Processed SOHO/EIT 284 image at 01:05 UTC on May 9. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be mostly quiet on May 9-11. A weak CME could arrive during the latter half of May 10 and cause a slight increase in geomagnetic activity.

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 poor. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (strong signal) with CPN Radio (Perú) weakly beneath. Propagation towards North America was somewhat better with WWZN on 1510 kHz noted with a fair signal, CJYQ 930 easily audible and a few other stations noted with weak signals].

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
10604 2004.05.03 1   S18W15 0010 AXX spotless all day
10605 2004.05.04 5 6 S12W58 0060 CSO  
10606 2004.05.07 1 3 S09E66 0220 HAX  
S399 emerged on
    S16W38     plage
S400 emerged on
  3 S11E13 0000 BXO  
Total spot count: 7 12
SSN: 37 42

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)
2003.04 126.4 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 58.1 (-1.4)
2003.11 140.8 67.3 (56.5 predicted, -1.6)
2003.12 114.9 46.5 (53.5 predicted, -3.0)
2004.01 114.1 37.2 (49.1 predicted, -4.4)
2004.02 107.0 46.0 (44.8 predicted, -4.3)
2004.03 112.0 48.9 (42.1 predicted, -2.7)
2004.04 101.2 39.3 (40.0 predicted, -2.1)
2004.05 89.7 (1) 11.8 (2) (36.8 predicted, -3.2)

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]