Solar Terrestrial Activity Report

Last major update issued on April 9, 2006 at 02:45 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 inactive to quiet on April 8. Solar wind speed ranged between 287 and 332 (all day average 312) km/sec. A high speed stream from CH219 arrived at ACE during the first hour of April 9.

Solar flux measured at 20h UTC on 2.8 GHz was 91.0. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6).
Three hour interval K indices: 10122112 (planetary), 10123212 (Boulder).

The background x-ray flux is at the class B2 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 10866 decayed slowly and quietly.
Region 10867 decayed further and was quiet.
Region 10869 decayed in the trailing spot section.

Spotted regions not numbered by NOAA/SEC:
[S643] This region rotated into view at the southeast limb on April 8. Location at midnight: S07E75.

Coronal mass ejections (CMEs)

April 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

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

Processed SOHO/EIT 284 image at 13:06 UTC on April 8. 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 9-10 due to effects from CH219, quiet to unsettled is likely 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. Propagation on long distance northeast-southwest paths is poor to fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay. Propagation was best to the northeastern part of South America and to the easternmost Caribbean islands.

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
10865 2006.03.28 3   S09W90 0180 CAO rotated out of view
10866 2006.03.29 4 5 S06W63 0080 CSO  
10867 2006.04.02 3 2 S16W67 0050 CAO classification was HAX at midnight
10868 2006.04.05     S07W45     plage
10869 2006.04.06 7 11 S12W04 0070 CAO  
S641 2006.04.04     S06W55     plage
S643 2006.04.08   1 S07E75 0050 HSX  
Total spot count: 17 19  
SSN: 57 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)
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 95.2 (1) 18.8 (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]