Solar Terrestrial Activity Report

Last major update issued on April 10, 2006 at 04:15 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 April 3, 2006)]

Recent activity

The geomagnetic field was active to major storm on April 9. Solar wind speed ranged between 330 and 698 (all day average 500) km/sec under the influence of a strong high speed stream from CH219.

Solar flux measured at 20h UTC on 2.8 GHz was 89.2 The planetary A index was 39 (STAR Ap - based on the mean of three hour interval ap indices: 38.6).
Three hour interval K indices: 45644455 (planetary), 44544435 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 3 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 10866 decayed slowly and quietly.
Region 10869 developed early in the day, then began to decay again.

Spotted regions not numbered by NOAA/SEC:
[S643] This region rotated into view at the southeast limb on April 8. Location at midnight: S07E62.

Coronal mass ejections (CMEs)

April 7-9: 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

A trans equatorial coronal hole (CH219) was in an Earth facing position on April 6-7.

Processed SOHO/EIT 284 image at 01:06 UTC on April10. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on April 10 due to effects from CH219 and quiet to unsettled on April 11-12.

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 to useless. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. On other frequencies the only stations noted were all from Uruguay and the southern part of Brasil, all had 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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10866 2006.03.29 2 1 S06W79 0040 CAO classification was HAX at midnight
10867 2006.04.02 2   S16W82 0030 HRX spotless
10868 2006.04.05     S07W58     plage
10869 2006.04.06 12 12 S12W16 0050 CAI classification was DAI at midnight, area 0080
S641 2006.04.04     S06W68     plage
S643 2006.04.08   1 S07E62 0040 HAX  
Total spot count: 16 14  
SSN: 46 44  

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)
2005.01 102.2 31.3 34.6 (-0.6)
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 (24.8 predicted, -1.0)
2005.11 86.3 18.0 (22.7 predicted, -2.1)
2005.12 90.7 41.2 (19.8 predicted, -2.9)
2006.01 83.4 15.4 (16.7 predicted, -3.1)
2006.02 76.5 4.7 (13.6 predicted, -3.1)
2006.03 75.4 10.8 (11.4 predicted, -2.2)
2006.04 94.5 (1) 20.3 (2) (10.7 predicted, -0.7)

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]