Solar Terrestrial Activity Report

Last major update issued on May 9, 2006 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 April 1, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 1, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 1, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update May 3, 2006)]

Recent activity

The geomagnetic field was quiet to active on May 8. Solar wind speed ranged between 467 and 607 (all day average 540) km/sec, decreasingly under the influence of a high speed stream from CH222.

Solar flux measured at 20h UTC on 2.8 GHz was 84.7. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.1).
Three hour interval K indices: 24311111 (planetary), 24321011 (Boulder).

The background x-ray flux is at the class A6 level.

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

Region 10880 was quiet and stable.
Region 10881 decayed and could become spotless today.
Region 10882 developed further and doubled the penumbral area.
Region 10883 decayed and could become spotless today or tomorrow.

Coronal mass ejections (CMEs)

May 6-8: No partly or fully Earth directed CMEs were observed in LASCO imagery.

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

Recurrent coronal holes (CH223 and CH224) in the northern hemisphere will rotate into an Earth facing position on May 8-11.

Processed SOHO/EIT 284 image at 19:06 UTC on May 8. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet on May 9-10. Unsettled to minor storm conditions are possible on May 11-14 due to high speed streams from CH223 and CH224.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)

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) Effects from a CME are likely to be observed at 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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Tonight Radio Cristal del Uruguay had an excellent signal at times. Propagation was best to Uruguay (1510 Radio San Carlos was good at LSR) and Argentina (many frequencies).

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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10878 2006.04.26     N12W48     plage
10879 2006.05.02     N16W73   \ plage
10880 2006.05.04 1 2 S09E08 0060 HAX  
10881 2006.05.05 2 1 S10E33 0010 AXX area was 0000 at midnight
10882 2006.05.06 7 9 S12W45 0130 DAO  
10883 2006.05.07 3 3 S04E56 0020 AXX formerly region S652
classification was CSO at midnight
S650 2006.05.03     S12W16     plage
Total spot count: 13 15  
SSN: 53 55  

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)
2005.02 97.2 29.2 33.9 (-0.7)
2005.03 89.9 24.5 33.5 (-0.4)
2005.04 86.0 24.2 31.6 (-1.9)
2005.05 99.3 42.7 28.9 (-2.7)
2005.06 93.7 39.3 28.8 (-0.1)
2005.07 96.4 40.1 29.1 (+0.3)
2005.08 90.5 36.4 27.4 (-1.7)
2005.09 91.1 21.9 25.8 (-1.6)
2005.10 77.0 8.5 25.5 (-0.3)
2005.11 86.3 18.0 (24.5 predicted, -1.0)
2005.12 90.7 41.2 (21.8 predicted, -2.7)
2006.01 83.4 15.4 (18.7 predicted, -3.1)
2006.02 76.5 4.7 (15.6 predicted, -3.1)
2006.03 75.4 10.8 (13.4 predicted, -2.2)
2006.04 89.0 30.2 (12.7 predicted, -0.7)
2006.05 88.5 (1) 14.7 (2) (12.2 predicted, -0.5)

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% lower.

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]