Last major update issued on April 12, 2010 at 03:40 UTC.
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The geomagnetic field was quiet to unsettled on April 11. Solar wind speed ranged between 347 and 452 km/s. A solar wind shock was observed at 12:18 UTC at SOHO, the arrival of the CME observed on April 8. Initially this caused unsettled geomagnetic conditions, however, early on April 12 the disturbance intensified to major storm levels and the ap index for 00-03 UTC was 94.
Solar flux measured at 20h UTC on 2.8 GHz was 74.6. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5). Three hour interval K indices: 10103333 (planetary), 10203333 (Boulder).
The background x-ray flux is at the class A3 level.
At midnight there was 1 spotted region on the visible solar disk.
Spotted regions not numbered by NOAA/SWPC:
[S761] This region emerged quickly in the southeast quadrant late on April 11. Location at midnight: S18E07
April 9-11: No obvious Earth directed CMEs were observed in LASCO or STEREO images.
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 poorly defined recurrent extension (CH399) of the southern polar coronal hole rotated across the central meridian on April 11-12.
Processed SOHO/EIT 195 image at 23:48 UTC on April 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 very poor. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet to major storm on April 12 due to CME effects. Quiet conditions are likely on April 13. April 14-16 could see quiet to unsettled conditions as a high speed stream from CH399 becomes the dominant solar wind source.
|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||SWPC
|Total spot count:||0||5|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
cycle 23 sunspot max.
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|2009.07||68.2||3.5||3.6 (+0.9)||5.49 / 4.55|
|2009.08||67.3||0.0||4.8 (+1.2)||5.70 / 4.89|
|2009.09||70.5||4.2||6.1 (+1.3)||3.88 / 3.61|
|2009.10||72.6||4.6||(7.4 predicted, +1.3)||3.66 / 3.56|
|2009.11||73.6||4.2||(8.9 predicted, +1.5)||2.45 / 2.63|
|2009.12||76.7||10.6||(10.8 predicted, +1.9)||1.41 / 1.92|
|2010.01||81.1||13.1||(12.6 predicted, +1.8)||2.93 / 3.07|
|2010.02||84.7||18.6||(14.7 predicted, +2.1)||4.15 / 4.61|
|2010.03||83.4||15.4||(17.1 predicted, +2.4)||4.58|
|2010.04||76.9 (1)||9.1 (2)||(19.4 predicted, +2.3)||(17.24)|
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.
3) Running average based on the daily SWPC ap indices. Values in red are based on official NGDC ap indices.
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.