Last major update issued on April 7, 2006 at 02:45 UTC.
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[Solar cycles 21-23 (last update April 1, 2006)]
[Solar cycles 1-20]
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[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 1, 2006)]
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[Archived reports (last update April 3, 2006)]
The geomagnetic field was quiet to active on April 6. Solar wind speed ranged between 357 and 441 (all day average 394) km/sec. Solar wind speed peaked early in the day, then decreased slowly after 09h UTC.
Solar flux measured at 20h UTC on 2.8 GHz was 98.9. The planetary A index
was 10 (STAR Ap - based on the mean of three hour interval ap
Three hour interval K indices: 13422212 (planetary), 23422211 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight there were 5 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 2 M class events were recorded during the day.
Region 10865 decayed further with only small spots remaining in what
was the intermediate spot section, The large penumbra still has many umbrae but
is more symmetrical than it was a day ago. There is a chance of another minor M
class flare. Flares: impulsive M1.4 at 0533
and M1.2 at 20:42 UTC.
Region 10866 was quiet and stable.
Region 10867 decayed further and was quiet.
Region 10868 decayed and could soon become spotless.
New region 10869 emerged in the southeast quadrant on April 5 and was numbered the following day by SEC. The region developed slowly on April 6.
April 4-6: No partly or fully Earth directed CMEs were observed in LASCO imagery.
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 moderately large trans equatorial coronal hole (CH219) will be in an Earth facing position on April 6-8.
Processed SOHO/EIT 284 image at 19:06 UTC on April 6. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to unsettled on April 7-8. Unsettled to minor storm conditions are likely on April 9-11 due to effects from CH219.
|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.
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. Dominant station tonight: Radio Cristal del Uruguay. On other frequencies most of the TA stations audible from Uruguay (best was 610 Radio Rural and 930 Radio Montecarlo) and Argentina (best reception on 950 kHz).
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|
|10865||2006.03.28||25||16||S11W60||0530||EKC||classification was DKO at midnight, area 0470|
|10867||2006.04.02||11||6||S16W39||0080||DSI||classification was DSO at midnight|
|10868||2006.04.05||6||5||S07W19||0040||DSO||classification was CRO at midnight, area 0020|
|10869||2006.04.06||7||7||S12E24||0030||BXO||formerly region S642
classification was CAO at midnight
|Total spot count:||55||40|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|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||96.0 (1)||14.7 (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.