Last major update issued on September 26, 2011 at 04:00 UTC. Last minor update posted at 19:05 UTC.
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Annotated geomagnetic activity charts - Carrington rotation 2113 [July-August 2011] - 2114 [August-September 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet on September 25. Solar wind speed ranged between 282 and 370 km/s. A weak solar wind shock was observed at SOHO at 11:12 UTC, the arrival of the CME associated with the X1 event in region 11302 on September 22.
Solar flux measured at 23h UTC on 2.8 GHz was 168.8 (increasing 67.6 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 10021212 (planetary), 11022322 (Boulder).
The background x-ray flux is at the class C2 level.
At midnight UTC the visible solar disk had 7 spotted regions (in 2K resolution SDO images).
Region 11301 [N19W11] was mostly unchanged and quiet.
Region 11302 [N13E37] relaxed a little as the strong magnetic delta structure in the central penumbra weakened on the northwestern side. The region remains capable of producing major flares. Flares: M4.4 at 02:33, C7.9 at 03:32, major M7.4/1N at 04:50, M3.1/1N at 08:49, C5.7 at 11:29, M3.7 at 15:33, M2.2 at 16:58 UTC.
Region 11303 [S27W80] developed further is it rotated to the southwest limb. The region could produce further M class flares while at the limb. Flares: M1.3 at 07:05 (not reported by SWPC), M1.5 at 09:35, M1.1 at 16:18 UTC.
Region 11304 [N12E08] developed slowly and was quiet.
New region 11305 [N12E70] rotated into view at the northeast limb on September 24 and was numbered by SWPC the next day.
Spotted regions not numbered by NOAA/SWPC:
[S1234] rotated into view at the northeast limb on September 25. Location at midnight: N13E87
[S1235] emerged in and old plage area in the northeast quadrant on September 25 with two tiny spots. Location at midnight: N18E17
Minor update added at 12:05 UTC on September 26: A strong solar wind shock was observed at ACE near 11:50 UTC. This is the arrival of the CME associated with the M7 LDE on September 24. Major geomagnetic storming is possible for the remainder of the day.
Minor update added at 19:05 UTC: The interplanetary magnetic field has at times been strongly southwards after 15h UTC. This resulted in very severe geomagnetic storming (Kp 8), the planetary 3-hour A index was 178 for the 15-18h interval. K9 - extremely severe geomagnetic storming is possible for the remainder of today and the first half of September 27.
September 23: No obviously Earth directed CMEs observed.
September 24: A huge, fast and wide (asymmetrical) full halo CME was observed in LASCO following an M7.1 LDE in region 11302. This CME will likely reach Earth on September 26 and cause active to major storm conditions.
September 25: Most of the CMEs observed during the day had their origin in region 11303, no large CMEs were observed from region 11302.
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 coronal hole (CH477) in the southern hemisphere will likely rotate into an Earth facing position on September 28.
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 fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be initially quiet on September 26. The CME observed on September 24 following an M7 flare in region 11302 could arrive during the day and cause unsettled to minor storm conditions. Quiet to active is likely on September 27 becoming quiet to unsettled on September 28.
|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||N25W98||0180||HSX||rotated out of view|
|1||1||N12E70||0060||HSX||HSX||formerly region S1231
|Total spot count:||48||102|
|Sunspot number:||108||172||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||78||135||(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):||65||57||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||132.7 (1)||90.1 (2A) / 108.1 (2B)||(56.7 predicted, +2.3)||(9.93)|
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.