Last major update issued on August 13, 2009 at 04:45 UTC.
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[Solar cycles 21-23 (last update October 4, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2007)]
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[Archived reports (last update June 14, 2009)]
The geomagnetic field was quiet on August 12. Solar wind speed ranged between 348 and 377 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 66.5. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.4). Three hour interval K indices: 21112211 (planetary), 22123111 (Boulder).
The background x-ray flux is below the class A1 level.
At midnight the visible solar disk was spotless.
August 10-12: No partially or fully Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A recurrent coronal hole (CH377) in the northern hemisphere will likely rotate into an Earth facing position on August 14-16. CH377 appears to be decaying and has become less well defined over the last days.
Processed STEREO-B 195 image at 19:55 UTC on August 11. The darkest areas on the solar disk are likely coronal holes.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet on August 13-16. A high speed stream from CH377 will likely cause quiet to active conditions on August 17-18.
|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.
Compare to the previous day's image.
Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.
|Active region||Date numbered||SWPC
|Location at midnight||Area||Classification||Comment|
|Total spot count:||0||0|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
very likely the sunspot minimum
|2009.02||70.0||1.4||(2.1 predicted, +0.3)|
|2009.03||69.2||0.7||(2.4 predicted, +0.3)|
|2009.04||69.7||1.2||(2.8 predicted, +0.4)|
|2009.05||70.5||2.9||(3.3 predicted, +0.5)|
|2009.06||68.6||2.6||(4.0 predicted, +0.7)|
|2009.07||68.2||3.5||(5.2 predicted, +1.2)|
|2009.08||67.1 (1)||0.0 (2)||(6.1 predicted, +0.9)|
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/SWPC) 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.