Last major update issued on September 18, 2011 at 06:35 UTC.
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[POES auroral activity level since October
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Annotated geomagnetic activity charts - Carrington rotation 2112 [July 2011] - 2113 [July-August 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet to major storm on September 17. Solar wind speed ranged between 346 and 535 km/s. A solar wind shock was observed at SOHO at 03:05, the arrival of the CME observed on Sept.13/14. After the shock the interplanetary magnetic field was at times moderate to strongly southwards causing major geomagnetic storming. The peak of the storm was during the 14-17h UTC interval when the 3-hour ap index reached 111.
Solar flux measured at 20h UTC on 2.8 GHz was 144.8 (increasing 43.9 over the last solar rotation). The planetary A index was 32 (STAR Ap - based on the mean of three hour interval ap indices: 32.4). Three hour interval K indices: 03346643 (planetary), 13444532 (Boulder).
The background x-ray flux is at the class B9 level.
At midnight UTC the visible solar disk had 12 spotted regions (in 2K resolution SDO images).
Region 11289 [N23W65] was mostly unchanged and quiet.
Region 11290 [S11W81] decayed slowly and was mostly quiet.
Region 11292 [N09W15] decayed slowly and quietly.
Region 11294 [S18W38] decayed slowly and could become spotless today.
Region 11295 [N22E05] was mostly quiet but has the potential to produce C and M class flares.
Region 11296 [N27E22] decayed slowly and quietly.
Region 11298 [N15E09] decayed slowly and quietly.
Region 11299 [S19E12] developed slowly and quietly.
Spotted regions not numbered by NOAA/SWPC:
[S1214] reemerged with a single spot on September 16. Location at midnight: S25W46
[S1218] emerged in the northwest quadrant on September 16 and developed significantly on September 17. The region could produce C flares. Location at midnight: N24W32
[S1219] rotated partly into view at the northeast limb late on September 17. C flares are possible, maybe even M flares. Location at midnight: N24E88
[S1220] emerged in the northwest quadrant on September 17. Location at midnight: N17W17
September 15-17: 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
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 on September 18-20 with a chance of unsettled intervals on Sept.18.
|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||N21W93||0010||BXO||rotated out of view|
|Total spot count:||48||134|
|Sunspot number:||138||254||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||84||173||(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):||83||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||123.0 (1)||61.7 (2A) / 108.8 (2B)||(56.7 predicted, +2.3)||(12.62)|
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.