Last major update issued on September 28, 2010 at 04:10 UTC. Minor update posted at 15:55 UTC.
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The geomagnetic field was quiet to unsettled on September 27. Solar wind speed ranged between 421 and 539 km/s under the influence of a weak coronal hole stream (probably from CH423).
Solar flux measured at 20h UTC on 2.8 GHz was 83.0 (up 8.4 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.8). Three hour interval K indices: 10002232 (planetary), 21103222 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight UTC the visible solar disk had 4 spotted regions.
Region 11108 added a couple of trailing spots and was quiet.
Region 11109 matured and lost a few spots. C flares
are possible.
Region 11110 decayed and could soon become spotless.
Spotted regions not numbered by NOAA/SWPC:
[S817] This region rotated into view at the northeast limb late in
the day. Location at midnight: N23E81
Minor update added at 15:55 UTC on September 28: Region 11110 has developed quickly today as new flux emerged, currently 7 spots are visible. The region was the source of a C1.7 flare at 09:48 UTC. A new region has emerged near the northwest limb and currently has 2 spots.
September 25-27: No obviously Earth directed CMEs were seen in LASCO or STEREO images.
Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago:
28 days ago
27 days ago
26 days ago
A small trans equatorial, recurrent coronal hole (CH423) was in an Earth facing position on September 24.
Image courtesy of SDO (NASA) and the AIA consortium. Annotations are my own. The darkest areas on the solar disk are likely coronal holes.
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 to fair.
The geomagnetic field is expected to be quiet to unsettled on September 28-29 when effects from CH423 are possible and quiet on September 30-31.
| 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 green.
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.
Compare to the previous day's image
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 (NASA) / AIA 4500 image |
Comment | |||
|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | STAR | SWPC | STAR | Current | Previous | |||||
| 11108 | 2010.09.16 | 1 | 3 | S30W72 | 0230 | HSX | CSO |
 |
 |
|
| 11109 | 2010.09.21 | 20 | 23 | N22E02 | 0420 | EKI | EHI |
 |
 |
|
| 11110 | 2010.09.26 | 1 | 2 | N20W19 | 0000 | AXX | BXO |
 |
 |
|
| S817 | 2010.09.27 | 1 | N23E81 | 0010 | AXX |
 |
||||
| Total spot count: | 22 | 29 | ||||||||
| SSN: | 52 | 69 | ||||||||
| Month | Average measured solar flux | International sunspot number (SIDC) | Smoothed sunspot number | Average ap (3) |
|---|---|---|---|---|
| 2000.04 | 184.2 | 125.5 | 120.8 cycle 23 sunspot max. |
|
| 2000.07 | 202.3 | 170.1 | 119.8 | |
| 2001.12 | 235.1 | 132.2 | 114.6 (-0.9) | |
| 2008.07 | 65.7 (SF minimum) | 0.5 | 2.8 (-0.4) | |
| 2008.12 | 69.2 | 0.8 | 1.7 (-) sunspot minimum |
3.25 |
| 2009.06 | 68.6 | 2.9 | 2.7 (+0.4) | 5.22 |
| 2009.07 | 68.2 | 3.2 | 3.6 (+0.9) | 5.49 / 4.55 |
| 2009.08 | 67.3 | 0.0 | 4.8 (+1.2) | 5.70 / 4.89 |
| 2009.09 | 70.5 | 4.3 | 6.2 (+1.4) | 3.88 / 3.61 |
| 2009.10 | 72.6 | 4.8 | 7.1 (+0.9) | 3.66 / 3.56 |
| 2009.11 | 73.6 | 4.1 | 7.6 (+0.5) | 2.45 / 2.63 |
| 2009.12 | 76.7 | 10.8 | 8.3 (+0.7) | 1.41 / 1.92 |
| 2010.01 | 81.1 | 13.2 | 9.3 (+1.0) | 2.93 / 3.07 |
| 2010.02 | 84.7 | 18.8 | 10.6 (+1.3) | 4.15 / 4.61 |
| 2010.03 | 83.4 | 15.4 | (12.3 predicted, +1.7) | 4.58 / 4.65 |
| 2010.04 | 75.9 | 7.9 | (13.9 predicted, +1.6) | 10.22 / 10.24 |
| 2010.05 | 73.8 | 8.8 | (15.2 predicted, +1.3) | 9.18 / 8.15 |
| 2010.06 | 72.5 | 13.5 | (16.6 predicted, +1.4) | 8.17 / 6.85 |
| 2010.07 | 79.8 | 16.1 | (18.3 predicted, +1.7) | 6.31 / 5.15 |
| 2010.08 | 79.2 | 19.6 | (19.5 predicted, +1.2) | 8.49 / 7.77 |
| 2010.09 | 80.3 (1) | 30.5 (2A) / 33.9 (2B) | (20.7 predicted, +1.2) | (5.44) |
1) Running average based on the
daily 20:00 UTC observed solar flux
value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number
(accumulated daily sunspots / month days). The official international sunspot number is typically
30-50% lower. 2B) Month average to date.
3) Running average based on the
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.