Last major update issued on September 16, 2011 at 04:25 UTC.
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[Solar cycles 21-24 (last update September 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 1, 2011)]
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[POES auroral activity level since October
2009 - updated September 15, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2112 [July 2011] - 2113 [July-August 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet on September 15. Solar wind speed ranged between 406 and 471 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 140.7 (increasing 42.5 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.4). Three hour interval K indices: 12111122 (planetary), 13212222 (Boulder).
The background x-ray flux is at the class B7 level.
At midnight UTC the visible solar disk had 11 spotted regions (in 2K resolution SDO images).
Region 11289 was mostly quiet and unchanged.
Region 11290 decayed slowly and quietly.
Region 11291 developed significantly with minor polarity intermixing observed.
Region 11292 was quiet and stable.
Region 11293 decayed and was mostly quiet.
Region 11294 was quiet and stable.
Region 11295 added many spots with polarity intermixing occurring throughout the region. C and M class flares are possible.
Region 11296 simplified magnetically while the largest penumbra increased its size.
Region 11297 decayed significantly but could still produce C flares and possibly a minor M class flare.
Region 11298 has mixed polarities with a difficult to determine boundary with region 11295.
Spotted regions not numbered by NOAA/SWPC:
[S1217] emerged in the southeast quadrant on September 14 and developed slowly on September 15. Minor polarity intermixing is visible. Location at midnight: S20E26
September 15: No obviously Earth directed CMEs observed.
September 13-14: A bright CME was observed following an eruption in region 11289 late on September 13. This CME could reach Earth on September 16.
Coronal hole history (since late October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
No obvious coronal holes are currently in or near potentially geoeffective positions.
The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using the new method, the extent and intensity of both holes are consistent with other data sources.
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 September 16. Late in the day there's a chance of a CME impact which could cause unsettled to active conditions for 12-18 hours. Quiet conditions are likely on September 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
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.
(Click on image for higher resolution image) Compare to the previous day's image
When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.
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 / HMI 4K continuum
image with polarity overlay
|1||S28W83||0010||HSX||rotated out of view|
|Total spot count:||57||154|
|Sunspot number:||167||264||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||106||208||(Sum of total spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)|
|Relative sunspot number (Wolf number):||100||87||k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|2010.06||72.5||13.6||16.4 (+0.9)||8.17 / 6.85|
|2010.07||79.8||16.1||16.7 (+0.3)||6.31 / 5.15|
|2010.08||79.2||19.6||17.4 (+0.7)||8.49 / 7.77|
|2010.09||81.1||25.2||19.6 (+2.2)||5.33 / 5.45|
|2010.10||81.6||23.5||23.2 (+3.6)||6.07 / 6.27|
|2010.11||82.5||21.5||26.5 (+3.3)||4.80 / 5.50|
|2010.12||84.2||14.4||28.8 (+2.3)||3.41 / 4.35|
|2011.01||83.6||19.1||31.0 (+2.2)||4.32 / 5.51|
|2011.02||94.6||29.4||33.4 (+2.4)||5.41 / 6.44|
|2011.03||115.0||56.2||(36.2 predicted, +2.8)||7.79 / 8.18|
|2011.04||112.6||54.4||(39.1 predicted, +2.9)||9.71 / 8.83|
|2011.05||95.8||41.6||(42.4 predicted, +3.3)||9.18 / 8.94|
|2011.06||95.8||37.0||(46.1 predicted, +3.7)||8.96|
|2011.07||94.2||43.9||(50.3 predicted, +4.2)||9.14|
|2011.08||101.7||50.6||(54.4 predicted, +4.1)||8.16|
|2011.09||120.2 (1)||51.3 (2A) / 102.6 (2B)||(56.7 predicted, +2.3)||(12.00)|
1) Running average based on the daily 20:00 UTC observed solar flux value at
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the preliminary 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.
SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.