Last major update issued on September 14, 2011 at 05:10 UTC. Minor update added at 20:10 UTC
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The geomagnetic field was quiet to unsettled on September 13. Solar wind speed ranged between 492 and 585 km/s under the decreasing influence of a high speed stream from CH475.
Solar flux measured at 20h UTC on 2.8 GHz was 129.4 (increasing 31.9 over the last solar rotation). The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 16.8). Three hour interval K indices: 44432113 (planetary), 44432222 (Boulder).
The background x-ray flux is at the class B5 level.
At midnight UTC the visible solar disk had 14 spotted regions (in 2K resolution SDO images).
Region 11287 developed slowly and was quiet.
Region 11289 was mostly quiet and unchanged. The region was the source of the most significant event of the day, a C2.9 long duration event peaking at 23:36 UTC. This event was associated with a bright CME (in STEREO-B) which appears to be partly Earth directed.
Region 11290 decayed slowly and quietly.
Region 11292 decayed slolwy and was quiet.
Region 11293 decayed slowly and quietly.
Region 11294 developed slowly and was quiet.
Region 11295 was mostly quiet but could produce minor M class events.
New region 11296 rotated into view at the northeast limb on September 12 and was numbered the next day by SWPC.
Spotted regions not numbered by NOAA/SWPC:
[S1196] rotated partly out of view at the southwest limb. Location at midnight: S19W83
[S1203] emerged in the northeast quadrant on September 10, became spotless quickly, then reemerged with tiny spots on September 12. Location at midnight: N07E27
[S1213] emerged in the southern hemisphere near the central meridian on September 13. Location at midnight: S18W01
[S1214] emerged in the southeast quadrant on September 13. Location at midnight: S26E04
[S1215] emerged in the southwest quadrant on September 13. Location at midnight: S17W37
[S1216] emerged in the northwest quadrant on September 13. Location at midnight: N22W56
Minor update posted at 20:10 UTC: Region 11297 (formerly S1215) has developed very quickly today and could produce M class flares. Region 11295 has developed significantly as well and could produce an M class flare. Solar flux at 17h UTC was above 140. The latest high resolution CHARMAP.
The CME observed early today after an eruption late on September 13, was a full halo CME based on LASCO images.
September 11-12: No obviously Earth directed CMEs observed.
September 13: A bright CME was observed following an eruption in region 11289 late in the day. This CME could reach Earth on September 16.
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
No obvious coronal holes are currently in or near potentially geoeffective positions.
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.
The geomagnetic field is expected to be quiet to unsettled on September 14 and quiet on September 15 and most of September 16. During the latter half of September 16 there's a chance of a CME impact which could cause unsettled 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
|2||9||N27E70||0050||DSO||DSO||formerly region S1210
|Total spot count:||38||114|
|Sunspot number:||118||254||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||78||160||(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):||71||84||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||116.9 (1)||40.9 (2A) / 94.5 (2B)||(56.7 predicted, +2.3)||(13.10)|
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.