Last major update issued on September 14, 2012 at 04:50 UTC.
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The geomagnetic field was quiet to unsettled on September 13. Solar wind speed at SOHO ranged between 337 and 411 km/s under the influence of a low speed stream associated with CH534.
Solar flux measured at 20h UTC on 2.8 GHz was 99.1 (increasing 4.0 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: 6.6). Three hour interval K indices: 32100221 (planetary), 32112322 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).
Region 11566 [N23W50] decayed slowly and quietly.
Region 11567 [N15W28] was quiet and stable.
Region 11569 [S12E27] has weak polarity intermixing and could produce a minor M class flare. The region produced several small C flares during the day.
Region 11571 [S13E47] was quiet and stable.
Spotted regions not numbered by NOAA/SWPC:
New region S1914 [N20E70] rotated into view.
New region S1915 [N23E37] emerged with a single spot.
New region S1916 [S18E01] emerged with tiny spots.
September 11-13: 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 coronal hole (CH535) in the southern hemisphere was Earth facing position on September 13.
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 to fair.
The geomagnetic field is expected to be quiet on September 14-15. Quiet to unsettled conditions are possible on September 16-17 due to effects from CH535. A small CME associated with a filament eruption in the northwest quadrant on September 13 was not observed as a halo CME in LASCO imagery and has only a small chance of causing any geomagnetic effects.
|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||39||17|
|Sunspot number:||44||109||87||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||29||54||32||(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):||26||38||48||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||125.5 (1)||42.2 (2A)/ 97.3 (2B)||(70.0 projected, +2.8)||(12.60)|
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.