Last major update issued on September 5, 2011 at 04:30 UTC.
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The geomagnetic field was quiet to unsettled on September 4. Solar wind speed ranged between 307 and 402 km/s. Another low speed stream, this time associated with CH474, arrived at SOHO just after 15h UTC.
Solar flux measured at 20h UTC on 2.8 GHz was 119.4 (increasing 17.9 over the last solar rotation). The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.4). Three hour interval K indices: 23212232 (planetary), 23112321 (Boulder).
The background x-ray flux is at the class C1 level.
At midnight UTC the visible solar disk had 8 spotted regions (in 2K resolution SDO images).
Region 11277 decayed slowly and quietly.
Region 11279 decayed slowly and could soon become spotless.
[Region 11280 displayed very impressive growth and became a DKC region before rotating out of view. A major flare is possible for the next 1-2 days while the region is just behind the northwest limb. Flares: C8.3 at 01:07, C9.0 at 04:53, estimated M1 at 05:47 (GOES xray data dropped out for about 40 minutes and the flare was recorded by SWPC as C4 with a peak at 06:15 when data returned. This was well into the decay phase of the flare. Comparison with other data sources (EVE, Wave) points to a magnitude just above M1), M3.2 at 11:45, C5.8 at 15:34 UTC]
Region 11281 decayed further and was quiet.
Region 11282 decayed slowly and quietly.
Region 11283 developed with a new penumbra forming to the north of the largest penumbra. The new penumbra has a magnetic delta structure. C flares and a minor M class flare is possible.
Region 11287 was quiet and stable.
Spotted regions not numbered by NOAA/SWPC:
[S1195] emerged in the northeast quadrant on September 3 and developed slowly on September 4. Location at midnight: N18E52
[S1196] emerged in the southeast quadrant on September 4. Location at midnight: S18E34
[S1197] emerged in the northwest quadrant on September 4. Location at midnight: N35W55
September 2-4: 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 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
|2||N13W91||0010||BXO||rotated out of view
|11286||2011.09.03||6||N20W75||0080||CSO||probably a duplicate of region 11282, location is near the leader spot of that region|
|Total spot count:||44||98|
|Sunspot number:||114||188||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||74||118||(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||62||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||116.3 (1)||15.8 (2A) / 118.8 (2B)||(56.7 predicted, +2.3)||(6.66)|
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.