Last major update issued on September 22, 2012 at 06:45 UTC.
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[Solar cycles 21-24 (last update September 8, 2012)] [Cycle 24 progress (last update September 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 8, 2012)]
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[Archived reports since January 2003 (last update September 3, 2012)]
[POES auroral activity level since October
2009 - updated September 8, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet to unsettled on September 21. Solar wind speed at SOHO ranged between 410 and 530 km/s under the influence of a high speed stream from CH536.
Solar flux measured at 20h UTC on 2.8 GHz was 116.9 (increasing 11.0 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.3). Three hour interval K indices: 22222321 (planetary), 11122311 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).
Region 11569 [S12W84] rotated quietly to the southwest limb.
Region 11571 [S14W62] decayed losing all trailing spots.
Region 11573 [N17W01] decayed slowly and quietly.
Region 11575 [N08E37] developed with negative polarity flux emerging in the northern part of the trailing spot section. Opposite poalrity spots are quite close in that section and further development could causea magnetic delta structure to form. C and minor M class flares are possible.
Region 11576 [S21E44] was quiet and stable.
Spotted regions not numbered by NOAA/SWPC:
S1924 [S26E08] added a tiny trailing spot and was quiet.
S1927 [N20E54] developed slowly and quietly.
New region S1929 [N05E66] emerged with a single spot.
New region S1930 [S09W08] emerged with a tiny spot.
New region S1931 [N22W22] emerged with a poorly defined spot.
September 19-21: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A trans equatorial coronal hole (CH536) was in an Earth facing position on September 17-19.
The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, 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 this method, the extent and intensity of both CHs 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 to unsettled on September 22 due to weak effects from CH536 and quiet on September 23-25.
|Coronal holes (1)||Coronal mass ejection (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. 0.5k 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 magnetic polarity overlay
|Total spot count:||14||49||23|
|Sunspot number:||74||149||103||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||37||72||46||(Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)|
|Relative sunspot number (Wolf number):||44||52||57||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
|2012.03||114.7||64.3||(67.3 projected, +0.4)||16.08|
|2012.04||113.0||55.2||(66.5 projected, -0.8)||10.10|
|2012.05||121.5||69.0||(64.4 projected, -2.1)||7.06|
|2012.06||119.6||64.5||(63.6 projected, -0.8)||10.08|
|2012.07||133.9||66.5||(64.6 projected, +1.0)||13.90|
|2012.08||115.4||63.1||(67.2 projected, +2.6)||7.96|
|2012.09||117.6 (1)||58.5 (2A) / 83.6 (2B) / 58.2 (2C)||(70.0 projected, +2.8)||(11.30)|
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. 2C) STAR SDO 1K Wolf number month to date.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC 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.