Last major update issued on September 4, 2011 at 04:55 UTC. Minor update posted at 06:40 UTC
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Annotated geomagnetic activity charts - Carrington rotation 2111 [June-July 2011] - 2112 [July 2011]
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The geomagnetic field was quiet to unsettled on September 3. Solar wind speed ranged between 291 and 426 km/s. A low speed, high density stream dominated the solar wind most of the day peaking at a wind speed near 370 km/s. Another disturbance was observed beginning at 23:00 UTC at SOHO with a sudden increase in solar wind speed (from 357 to 426 km/s). This may have been related to the arrival of a weak CME observed early on September 1 after an event in region 11282 between 00:20 and 00:50 UTC.
Solar flux measured at 20h UTC on 2.8 GHz was 118.7 (increasing 13.3 over the last solar rotation). The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 12.5). Three hour interval K indices: 33232333 (planetary), 33242212 (Boulder).
The background x-ray flux is at the class B7 level.
At midnight UTC the visible solar disk had 8 spotted regions (in 2K resolution SDO images).
Region 11277 decayed and lost all penumbra.
Region 11279 decayed further and was quiet.
Region 11280 lost all spots in the southern spot section while more flux emerged in the northern spot section. Polarities are intermixed and an M class flare is possible before the region rotates out of view late today. Flares: C1.0 at 03:22, C1.0 at 14:12, C2.5 at 17:36, C1.2 at 20:10 UTC. The region was the source of a C8.3 flare at 01:07 UTC on September 4.
Region 11281 decayed further and simplified magnetically. Flare: C2.4 at 07:56 UTC
Region 11282 decayed slowly and quietly.
Region 11283 developed slowly and was quiet. C class flaring is possible.
New region 11287 rotated into view at the southeast limb on September 2 and was numbered the next day by SWPC. Slow development was observed in September 3 and the region could produce C flares.
[SWPC has numbered region 11286 and set its location to near the leader spot of region 11282. SWPC "observed" the same number of spots as in region 11282 and it seems that they have mistakenly counted the same spots twice and inflated their sunspot number by 18.]
Spotted regions not numbered by NOAA/SWPC:
[S1195] emerged in the northeast quadrant on September 3. Location at midnight: N19E63
Minor update added at 06:40 UTC: Region 11280 has been very activy today. In addition to the flare mentioned above, a C9.0 flare was recorded at 04:51. Unfortunately there was no GOES xray data during the next flare. Based on Wave and EVE data this event peaked sometime between 05:40 and 05:50 UTC with an estimated magnitude at M2. Further M class flares are likely as the region rotates to the limb, the northwesternmost penumbra is growing quickly.
September 2-3: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.
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 coronal hole (CH474) in the southern hemisphere was in an Earth facing position on September 1. A recurrent coronal hole (CH475) in the northern hemisphere will likely rotate into an Earth facing position on September 8.
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 poor to fair.
The geomagnetic field is expected to be quiet to unsettled on September 4-5 and quiet on September 6-7.
|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
|3||8||S30E64||0030||CAO||DAO||formerly region S1192
|11286||2011.09.03||8||N20W57||0080||DSO||probably a duplicate of region 11282, location near leader spot of that region|
|Total spot count:||59||101|
|Sunspot number:||139||181||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||94||129||(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||60||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||115.3 (1)||12.0 (2A) / 120.3 (2B)||(56.7 predicted, +2.3)||(6.08)|
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.