Last major update issued on September 17, 2011 at 05:55 UTC.
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The geomagnetic field was very quiet on September 16. Solar wind speed ranged between 347 and 453 km/s. A solar wind shock was observed at ACE near 03h UTC on September 17. This was the arrival of the CME observed on Sept.13/14.
Solar flux measured at 20h UTC on 2.8 GHz was 143.1 (increasing 42.6 over the last solar rotation). The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.1). Three hour interval K indices: 10001101 (planetary), 11012221 (Boulder).
The background x-ray flux is at the class C1 level.
At midnight UTC the visible solar disk had 13 spotted regions (in 2K resolution SDO images).
Region 11289 [N23W52] was mostly unchanged.
Flare: C2.6 long duration event peaking at 23:51 UTC. This event was
associated with a CME which is likely not going to become geoeffective.
Region 11290 [S12W68] developed slowly and could produce further C flares. Flares: C9.3 at 11:36, C2.0/1F at 15:08, C1.4 at 22:13 UTC
Region 11291 [N22W82] developed further and could produce a C flare as it rotates over the northwest limb.
Region 11292 [N10W04] was quiet and stable.
Region 11293 [N17W63] decayed quietly retaining only 2 spots.
Region 11294 [S17W30] decayed slowly and quietly.
Region 11295 [N22E18] decayed losing quite a few spots. There's still polarity intermixing and C and M flares are possible. Flare: C4.5 at 02:57 UTC.
Region 11296 [N26E34] decayed but could produce C flares. Flare: C2.2 at 17:21 UTC.
Region 11297 [S18W79] decayed further as it rotated to the southwest limb. Flares: C7.8/1F at 00:19, C4.7/1F at 04:39, C2.2 at 08:46, C1.5 at 19:31 UTC.
Region 11298 [N16E24] decayed slowly and quietly.
New region 11299 [S19E12] emerged in the southeast quadrant on September 14 and received an SWPC number 2 days later.
Spotted regions not numbered by NOAA/SWPC:
[S1214] reemerged with a single tiny spot. Location at midnight: S25W31
[S1218] emerged in the northwest quadrant on September 16. Location at midnight: N24W16
September 15-16: No obviously Earth directed CMEs observed.
September 13-14: A bright CME was observed following an eruption in region 11289 late on September 13.
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
No obvious coronal holes are currently in or near potentially geoeffective positions.
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 active on September 17 due to CME effects. Quiet conditions are likely on September 18-19.
|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
|Total spot count:||63||145|
|Sunspot number:||173||275||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||107||188||(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):||104||91||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||121.7 (1)||57.1 (2A) / 107.0 (2B)||(56.7 predicted, +2.3)||(11.38)|
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.