Last major update issued on September 12, 2011 at 04:30 UTC.
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The geomagnetic field was quiet to unsettled on September 11. Solar wind speed ranged between 539 and 608 km/s under the influence of a high speed stream from CH475.
Solar flux measured at 20h UTC on 2.8 GHz was 121.3 (increasing 30.9 over the last solar rotation). The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.4). Three hour interval K indices: 32113213 (planetary), 32213313 (Boulder).
The background x-ray flux is at the class B7 level.
At midnight UTC the visible solar disk had 12 spotted regions (in 2K resolution SDO images).
Region 11283 rotated to the northwest limb. Flares:
C6.6 at 08:51, C1.9 at 13:26, C1.7 at 19:49, C1.1 at 21:25 UTC
Region 11287 was quiet and stable.
Region 11289 decayed slightly losing the penumbra which had been located to the southwest of the large penumbra.
Region 11290 developed slowly and has minor polarity intermixing. C flares are possible.
New region 11292 emerged in the northeast quadrant on September 11.
Spotted regions not numbered by NOAA/SWPC:
[S1196] reemerged with several spots on September 11. Location at midnight: S21W53
[S1201] emerged in the southeast quadrant on September 10. Location at midnight: S17E43
[S1205] rotated into view at the northeast limb on September 11. Location at midnight: N22E83
[S1206] emerged in the northeast quadrant on September 11. Location at midnight: N15E11
[S1207] emerged in the northeast quadrant on September 11. Location at midnight: N17E04
[S1208] emerged in the northwest quadrant on September 11. Location at midnight: N16W58
[S1209] emerged in the northwest quadrant on September 11. Location at midnight: N21W42
September 9: No obviously Earth directed CMEs were observed. There was a
CME after the M2 event in region 11283 but its path makes any terrestrial
effects unlikely. Several backsided CMEs were noted.
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: 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. Propagation on long distance northeast-southwest paths is fair to good.
The geomagnetic field is expected to be quiet to active on September 12-13 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.
|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
|11292||2011.09.11||2||7||N08E66||0040||BXO||CRO||formerly region S1203|
|Total spot count:||34||85|
|Sunspot number:||94||205||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||59||119||(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):||56||68||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||115.2 (1)||33.8 (2A) / 92.1 (2B)||(56.7 predicted, +2.3)||(11.52)|
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.