Last major update issued on September 27, 2011 at 04:40 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 to very severe storm on September 26. Solar wind speed ranged between 319 and 674 km/s. A strong solar wind shock was observed at SOHO at 12:02 UTC, the arrival of the CME associated with the M7 event in region 11302 on September 24. Initially the geomagnetic effects were not very strong, however, between 15 and 19h UTC the interplanetary magnetic field swung strongly to very strongly southwards causing very severe geomagnetic storming.
Solar flux measured at 23h UTC on 2.8 GHz was 148.2 (increasing 46.9 over the last solar rotation). The planetary A index was 59 (STAR Ap - based on the mean of three hour interval ap indices: 58.8). Three hour interval K indices: 10015884 (planetary), 21125654 (Boulder).
The background x-ray flux is at the class B8 level.
At midnight UTC the visible solar disk had 7 spotted regions (in 2K resolution SDO images).
Region 11301 [N18W23] decayed slowly and quietly retaining only
rudimentary penumbra on the largest spot.
Region 11302 [N14E23] relaxed further as the magnetic delta structure in the central penumbra decayed. The leading penumbra stretched out and could soon merge with the central penumbra. If that happens we could again see a situation with frequent and strong flaring.
Region 11304 [N12W06] lost a few spots and was quiet.
Region 11305 [N12E57] added a few trailing spots and was quiet.
New region 11306 [N13E76] rotated into view late on September 25 and was numbered the next day by NOAA/SWPC.
Spotted regions not numbered by NOAA/SWPC:
[S1236] emerged in the southeast quadrant on September 26. Further development could cause CH477 to close. Location at midnight: S17E29
[S1237] emerged in the nortrhwest quadrant on September 26. Location at midnight: N13W17
September 25-26: 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 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 very poor. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to severe storm on September 27. Quiet to unsettled is likely on September 28-29
|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||S28W90||0060||HSX||rotated out of view|
|1||1||N13E74||0030||HSX||HSX||formerly region S1234|
|Total spot count:||54||77|
|Sunspot number:||114||147||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||89||103||(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):||68||49||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||133.3 (1)||93.9 (2A) / 108.3 (2B)||(56.7 predicted, +2.3)||(11.80)|
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.