Last major update issued on September 6, 2011 at 04:10 UTC. Minor update posted at 18:40 UTC.
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The geomagnetic field was quiet on September 5. Solar wind speed ranged between 299 and 403 km/s under the influence of a low speed stream from CH474.
Solar flux measured at 20h UTC on 2.8 GHz was 118.7 (increasing 21.2 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.5). Three hour interval K indices: 20102222 (planetary), 10112322 (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 was quiet and stable and will rotate over the northwest
[Region 11280 produced several C flares and 2 M flares (M1.6 at 04:08, M1.2 at 07:52 UTC) from behind the northwest limb.
Region 11281 decayed further and was quiet.
Region 11282 was quiet and stable. The region will rotate out of view today.
Region 11283 developed slowly and was mostly quiet. There's a magnetic delta structure in a penumbra to the north of the largest penumbra. M flares are possible. The region produced a major M5.3/1B flare at 01:50 UTC on September 6. A moderate type II radio sweep was recorded. A CME was observed in STEREO images soon after the flare. The CME appears to be fast and could impact Earth late on September 7 or early on September 8. Proton fluxes are increasing.
Region 11287 was quiet and stable.
New region 11288 emerged in the northeast quadrant on September 3 and was numbered 2 days later by SWPC. The region decayed slowly on September 5.
Spotted regions not numbered by NOAA/SWPC:
[S1196] emerged in the southeast quadrant on September 4. Location at midnight: S19E19
[S1198] began to rotate into view at the northeast limb late on September 5. Location at midnight: N25E87
Minor update added at 18:40 UTC on September 6: The CME observed earlier today was a halo CME, however, most of the ejected material was observed over the northern limbs. The CME was slower than first estimated and could reach Earth late on September 8 causing unsettled to active conditions with a chance of minor storming. A larger CME was observed later in the morning from a source behind the northwest limb.
September 3-5: No obviously Earth directed CMEs were observed in LASCO or
September 6: The CME associated with the major M5 flare in region 11283 appears to be fast in initial images and could impact Earth late on September 7 or early on September 8.
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 trans equatorial coronal hole (CH475) 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 to fair. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet on September 6 and most of September 7. Late on September 7 or early on September 8 the CME from the major flare early on September could reach Earth and cause active to major storm conditions.
|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
|11288||2011.09.03||3||2||N18E34||0010||BXO||AXX||formerly region S1195|
|Total spot count:||42||71|
|Sunspot number:||102||151||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||62||94||(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):||61||68||k * (sunspot number). k = 0.6 for SWPC. k = 0.45 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||116.6 (1)||19.2 (2A) / 115.4 (2B)||(56.7 predicted, +2.3)||(6.43)|
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.