Last major update issued on September 7, 2011 at 04:50 UTC.
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The geomagnetic field was quiet on September 6. Solar wind speed ranged between 351 and 431 km/s, weakly under the influence of a low speed stream from CH474.
Solar flux measured at 20h UTC on 2.8 GHz was 111.5 (increasing 21.2 over the last solar rotation). The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.6). Three hour interval K indices: 12222112 (planetary), 23222222 (Boulder).
The background x-ray flux is at the class B6 level.
At midnight UTC the visible solar disk had 7 spotted regions (in 2K resolution SDO images).
Region 11281 was quiet with a few small spots emerging in the northern
part of the region.
Region 11283 became more complex as the major penumbrae merged into one penumbra. There's a strong magnetic delta structure in the northern part of this penumbra. Further major flares are possible. Flares: major M5.3/1B at 01:50 (associated with a strong type II radio sweep and a halo CME. Most of the ejected material was observed over the northern limbs and there's a chance the core of the CME will not reach Earth), major impulsive X2.1 flare at 22:20 UTC. The latter event was associated with a slow and wide CME with Earth apparently in the path of the core CME.
Region 11287 was quiet and stable.
Region 11288 was quiet and stable.
New region 11289 rotated into view at the northeast limb.
Spotted regions not numbered by NOAA/SWPC:
[S1193] reemerged with a single tiny spot on September 6. Location at midnight: N24W28
[S1196] emerged in the southeast quadrant on September 4. Location at midnight: S21E07
September 4-5: No obviously Earth directed CMEs were observed in LASCO or
September 6: The CME associated with the major M5 flare in region 11283 was mainly directed outside a direct Earth path. A minor disturbance is possible starting late on September 8 or during the first half of September 9. A wider CME was observed following the X2 flare. This CME will likely impact Earth, probably arriving during the latter half of September 9.
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) will likely rotate into an Earth facing position on September 8-9.
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 fair. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet to unsettled on September 7-8. September 9 could see the arrival of 2 CMEs, the latter has the potential to cause active to major storm conditions. Disturbed conditions are likely to continue on September 10. On September 11-12 a high speed stream from CH475 could cause quiet to active conditions.
|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
|1||1||N18W93||0060||HSX||rotated out of view|
|Total spot count:||33||67|
|Sunspot number:||93||137||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||53||92||(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||62||k * (sunspot number). k = 0.6 for SWPC. k = 0.45 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||115.8 (1)||22.3 (2A) / 111.7 (2B)||(56.7 predicted, +2.3)||(6.46)|
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.