Last major update issued on September 13, 2010 at 03:50 UTC.
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[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 4, 2010)]
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[Archived reports (last update September 4, 2010)]
The geomagnetic field was very quiet on September 12. Solar wind speed ranged between 288 and 339 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 78.3 (down 6.4 over the last solar rotation). The planetary A index was 1 (STAR Ap - based on the mean of three hour interval ap indices: 1.1). Three hour interval K indices: 00000001 (planetary), 00100100 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight UTC the visible solar disk had 2 spotted regions.
Region 11106 rotated fully into view revealing several small trailing
spots. C flares are possible.
New region 11107 rotated into view at the northeast limb on September 11, developed slowly early on September, then decayed slowly.
September 10 and 12: No obviously Earth directed CMEs were seen in LASCO or STEREO
September 11: A filament eruption (centered in a large plage area) early in the day in the northeast quadrant was associated with a partial halo CME in LASCO 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 small recurrent coronal hole (CH421) in the northern hemisphere was Earth facing on September 7-8. This coronal hole didn't cause a disturbance during the previous rotation.
Image courtesy of SDO (NASA) and the AIA consortium. Annotations are my own. 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 mostly quiet on September 13-14 with a slight possibility of occasional unsettled intervals due to coronal hole effects. On September 15 the flank of a CME observed on September 11 could reach Earth and cause unsettled intervals.
|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||Spot count||Location at midnight||Area||Classification||SDO (NASA) / AIA 4500
|11107||2010.09.12||1||1||N33E62||0010||AXX||AXX||formerly region S813|
|Total spot count:||6||11|
|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||3.2||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||4.3||6.2 (+1.4)||3.88 / 3.61|
|2009.10||72.6||4.8||7.1 (+0.9)||3.66 / 3.56|
|2009.11||73.6||4.1||7.6 (+0.5)||2.45 / 2.63|
|2009.12||76.7||10.8||8.3 (+0.7)||1.41 / 1.92|
|2010.01||81.1||13.2||9.3 (+1.0)||2.93 / 3.07|
|2010.02||84.7||18.8||10.6 (+1.3)||4.15 / 4.61|
|2010.03||83.4||15.4||(12.3 predicted, +1.7)||4.58 / 4.65|
|2010.04||75.9||7.9||(13.9 predicted, +1.6)||10.22 / 10.24|
|2010.05||73.8||8.8||(15.2 predicted, +1.3)||9.18 / 8.15|
|2010.06||72.5||13.5||(16.6 predicted, +1.4)||8.17 / 6.85|
|2010.07||79.8||16.1||(18.3 predicted, +1.7)||6.31 / 5.15|
|2010.08||79.2||19.6||(19.5 predicted, +1.2)||8.49|
|2010.09||77.5 (1)||11.9 (2A) / 29.7 (2B)||(20.7 predicted, +1.2)||(4.86)|
1) Running average based on the
daily 20:00 UTC observed solar flux
value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the daily SWPC ap indices. Values in red are based on the official NGDC ap indices.
This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.