Last major update issued on April 21, 2008 at 04:25 UTC.
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 April 7, 2008)]
The geomagnetic field was quiet on April 20. Solar wind speed ranged between 457 and 541 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 70.8. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.0). Three hour interval K indices: 20001212 (planetary), 20111321 (Boulder).
The background x-ray flux is below the class A1 level.
At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low.
April 18-20: No partially or fully Earth directed CMEs were observed.
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 (CH320) in the northern hemisphere was in an Earth facing position on April 18-20. A recurrent trans equatorial coronal hole (CH321) will likely rotate into an Earth facing position on April 21-23.
Processed SOHO/EIT 195 image at 00:24 UTC on April 21. 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 poor. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet most of April 21. A high speed stream from CH320 could cause unsettled to minor storm conditions late today or early on April 22 and on April 23. A high speed stream from CH321 will likely dominate the solar wind April 24-26 and cause unsettled to active conditions.
|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|
|10991||2008.04.19||2||0||S10E15||0020||AXX||spotless at midnight|
|Total spot count:||2||0|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2007.10||67.4||0.9||(6.3 predicted, +0.4)|
|2007.11||69.6||1.7||(6.5 predicted, +0.2)|
|2007.12||78.5||10.1||(6.6 predicted, +0.2)|
|2008.01||74.3||3.4||(7.0 predicted, +0.4)|
|2008.02||71.1||2.1||(7.9 predicted, +1.0)|
|2008.03||72.9||9.3||(9.4 predicted, +1.5)|
|2008.04||70.6 (1)||3.4 (2)||(10.8 predicted, +1.4)|
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.