Last major update issued on September 13, 2011 at 05:00 UTC.
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The geomagnetic field was unsettled to minor storm on September 12. Solar wind speed ranged between 559 and 636 km/s under the influence of a high speed stream from CH475.
Solar flux measured at 20h UTC on 2.8 GHz was 123.9 (increasing 30.9 over the last solar rotation). The planetary A index was 27 (STAR Ap - based on the mean of three hour interval ap indices: 26.8). Three hour interval K indices: 44443445 (planetary), 44444334 (Boulder).
The background x-ray flux is at the class B6 level.
At midnight UTC the visible solar disk had 14 spotted regions (in 2K resolution SDO images).
Region 11287 was quiet and stable.
Region 11289 was quiet and mostly unchanged.
Region 11290 developed further and has a weak magnetic delta structure in the central penumbra. C flares are possible.
Region 11291 reemerged with a few tiny spots on September 12.
Region 11292 developed slowly and could produce further C flares. Flares: C1.7 at 02:26, C2.0 at 03:29 UTC.
New region 11293 emerged in the northeast quadrant on September 11 and was numbered the next day by SWPC.
New region 11294 emerged in the southeast quadrant on September 10 and was noticed by SWPC 2 days later.
New region 11295 rotated into view at the northeast limb on September 11 and was assigned an SWPC number the following day. It's uncertain if it was this region or one just behind the northeast limb which was the source of a long duration C9.9 event peaking at 20:51 UTC.
Spotted regions not numbered by NOAA/SWPC:
[S1196] was quiet and stable. Location at midnight: S20W77
[S1203] emerged in the northeast quadrant on September 10, became spotless quickly, then reemerged with tiny spots on September 12. Location at midnight: N08E38
[S1208] emerged in the northwest quadrant on September 11. Location at midnight: N15W72
[S1210] rotated into view at the northeast limb on September 12. Location at midnight: N27E82
[S1211] emerged in the southwest quadrant on September 12. Location at midnight: S33W12
[S1212] emerged in the northeast quadrant on September 12. Location at midnight: N38E18
September 10: A large filament eruption in the northwest quadrant early
in the day was associated with at least a partial halo CME. A filament eruption
starting at 07h UTC to the south of region 11289 may have been associated with a
potentially Earth directed CME.
September 11-12: No obviously Earth directed CMEs observed.
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
A recurrent trans equatorial coronal hole (CH475) was in an Earth facing position on September 8-10. Another and smaller trans equatorial coronal hole (CH476) was Earth facing on September 11 as it decayed and closed.
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 to very poor. Propagation on long distance northeast-southwest paths is good.
The geomagnetic field is expected to be quiet to minor storm on September 13 due to effects from CH475. CME impacts are possible on September 13 and could cause an increase in disturbance levels. Quiet to unsettled conditions are likely on September 14-15.
|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
|2||8||S18E27||0010||BXO||CRO||formerly region S1201|
|Total spot count:||27||104|
|Sunspot number:||97||244||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||57||145||(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):||58||81||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||115.9 (1)||37.0 (2A) / 92.5 (2B)||(56.7 predicted, +2.3)||(12.79)|
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.