Last major update issued on September 4, 2012 at 05:30 UTC.
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[Solar cycles 21-24 (last update August 6, 2012)] [Cycle 24 progress (last update September 2, 2012) ]
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[POES auroral activity level since October
2009 - updated August 5, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was active to major storm on September 3. Solar wind speed at SOHO ranged between 287 and 453 km/s. A solar wind shock was observed at ACE at 11:23 UTC, the arrival of the August 31 CME.
Solar flux measured at 20h UTC on 2.8 GHz was 141.6 (increasing 13.5 over the last solar rotation). The Potsdam WDC planetary A index was 38 (STAR Ap - based on the mean of three hour interval ap indices: 38.3). Three hour interval K indices: 44446554 (planetary), 33645435 (Boulder).
The background x-ray flux is at the class B7 level.
At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).
Region 11553 [S21W81] was mostly quiet as it rotated to the southwest
Region 11558 [N15W14] developed slowly and quietly.
Region 11560 [N03W32] still has a magnetic delta structure centrally, however, the region only managed to produce a few small C flares. A minor M class flare is possible. The region is decaying slowly and lost a large part of its umbral area during the day.
Region 11561 [S10W38] gained a few spots, however, the two northernmost spots could be a separate group.
Region 11562 [S18W03] was quiet and stable.
Region 11563 [S26E15] decayed slowly and quietly.
Region 11564 [S14E28] developed further and has significant polarity intermixing. An M class flare is possible. The region was the most active one on the visible disk producing a number of small C flares.
New region 11565 [N11E22] emerged on September 2 and was numbered by SWPC the next day. The region developed on September 3.
New region 11566 [N22E79] rotated into view.
Spotted regions not numbered by NOAA/SWPC:
S1897 [S22W08] developed slowly and quietly.
New region S1898 [N09E26] was split off from AR 11565.
New region S1899 [N10W30] emerged with a tiny spot.
September 1, 3: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
September 2: A full faint halo CME was observed early in the day and could reach Earth on September 5.
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 small northern hemisphere coronal hole (CH532) was in an Earth facing position on September 2-3, CH532 appears to have closed during the latter half of September 3.
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 good.
The geomagnetic field is expected to be quiet to minor storm on September 4-6 due to CME effects and quiet to unsettled on September 7.
|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
|N17W18||originally AR 11558|
|Total spot count:||66||174||88|
|Sunspot number:||156||294||198||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||102||211||125||(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):||94||103||109||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)||7.53|
|2012.09||143.2 (1)||12.4 (2A)/ 128.0 (2B)||(70.0 projected, +2.8)||(20.58)|
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 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.