Last major update issued on August 31, 2011 at 04:30 UTC.
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The geomagnetic field was quiet on August 30. Solar wind speed ranged between 348 and 431 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 101.3 (decreasing 18.6 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.0). Three hour interval K indices: 10012121 (planetary), 21112311 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight UTC the visible solar disk had 11 spotted regions (in 2K resolution SDO images).
Region 11274 developed slowly. Further C flares are possible.
Flares: C1.9 at 03:12, C1.1 at 05:14 UTC.
Region 11275 was quiet and stable.
Region 11277 was quiet and stable.
Region 11279 was quiet and stable.
Region 11280 was quiet and stable.
Region 11281 developed slowly with poor separation between opposite polarity spots along the neutral line. Further C flares are possible. Flare: C5.5/1|F at 22:46 UTC
New region 11282 emerged in the northeast quadrant on August 29 and was number the next day by SWPC. There's some polarity intermixing.
New region 11283 rotated into view at the northeast limb.
New region 11284 was first observed with spots on August 25, then became spotless, reemerged on August 30 and was noticed by SWPC.
Spotted regions not numbered by NOAA/SWPC:
[S1189] emerged in the northwest quadrant on August 29. Location at midnight: N28W36
[S1190] emerged in the southeast quadrant on August 30. Location at midnight: S13E48
August 28-30: 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 will likely rotate into an Earth facing position on September 1.
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 quiet on August 31 - September 3. Quiet to unsettled conditions are possible on September 4-5 due to effects from CH474.
|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
|11276||2011.08.23||N20W49||region should be deleted, spot was the trailing spot of region 11274|
|1||7||S19W57||0010||AXX||CRO||formerly region S1182|
|1||3||N12E71||0060||HSX||CSO||formerly region S1186
|Total spot count:||19||57|
|Sunspot number:||89||167||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||44||84||(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):||53||55||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)|
|2010.05||73.8||8.7||15.5 (+1.5)||9.18 / 8.15|
|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||(33.6 predicted, +2.6)||5.41 / 6.44|
|2011.03||115.0||56.2||(36.6 predicted, +3.0)||7.79 / 8.18|
|2011.04||112.6||54.4||(39.4 predicted, +2.8)||9.71 / 8.83|
|2011.05||95.8||41.6||(42.7 predicted, +3.3)||9.18 / 8.94|
|2011.06||95.8||37.0||(46.5 predicted, +3.8)||8.96|
|2011.07||94.2||43.9||(50.6 predicted, +4.1)||9.14|
|2011.08||101.5 (1)||62.1 (2A) / 64.2 (2B)||(54.8 predicted, +4.2)||(8.36)|
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.