Last major update issued on April 7, 2009 at 04:20 UTC.
[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[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)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update January 3, 2009)]
The geomagnetic field was very quiet on April 6. Solar wind speed ranged between 345 and 383 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 68.8. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.6). Three hour interval K indices: 10011101 (planetary), 00022221 (Boulder).
The background x-ray flux is below the class A1 level.
At midnight the visible solar disk was spotless.
April 4-6: No partially or fully Earth directed CMEs were observed in LASCO 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 trans equatorial coronal hole (CH366) was in an Earth facing position on April 5-7.
Processed SOHO/EIT 195 image at 00:24 UTC on April 7. 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 good. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet on April 7 and the first half of April 8. Quiet to minor storm conditions are possible on April 8-10 due to effects from CH366.
|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.
|2008.10||68.3||2.9||(1.9 predicted, -0.4)
sunspot minimum candidate month
|2008.11||68.6||4.1||(1.8 predicted, -0.1)
sunspot minimum candidate month
|2008.12||69.2||0.8||(1.9 predicted, +0.1)|
|2009.01||69.8||1.5||(2.2 predicted, +0.3)|
|2009.02||70.0||1.4||(2.7 predicted, +0.5)|
|2009.03||69.2||0.7||(3.4 predicted, +0.7)|
|2009.04||70.2 (1)||0.0 (2)||(4.1 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/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.