Last major update issued on December 18, 2011 at 07:05 UTC.
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The geomagnetic field was quiet on December 17. Solar wind speed ranged between 269 and 277 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 119.6 (decreasing 20.3 over the last solar rotation). The planetary A index was 0 (STAR Ap - based on the mean of three hour interval ap indices: 0.5). Three hour interval K indices: 00000001 (planetary), 00001100 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 11 spotted regions (in 2K resolution SDO images).
Region 11374 [S17W50] was quiet and stable.
Region 11375 [N10W57] decayed slowly and quietly.
Region 11376 [N26E06] decayed slowly and quietly.
Region 11377 [N14E04] was quiet and stable.
Region 11378 [S15W22] decayed slowly and quietly.
New region 11379 [S28W22] emerged in the southwest quadrant on December
16 and got an SWPC number the next day. Although this is a reversed polarity
region, there has been no significant development over the last day.
New region 11380 [S20E71] rotated into view at the southeast limb on
December 16 and was numbered by SWP the next day.
Spotted regions not reported by NOAA/SWPC:
[S1373] emerged in the southeast quadrant on December 16. Location at midnight:
S17E44
[S1376] emerged quickly in the southeast quadrant on December 17. C
flares are possible.
Location at midnight: S17E37
[S1377] emerged in the northeast quadrant on December 17. Location at
midnight: N08E07
[S1378] emerged in the northern hemisphere near the central meridian on
December 17. Note that SWPC considers this to be region 11376. The region is
somewhat unstable and is likely to produce further C class flares.
Flares: C1.2 at 05:01, C3.2 at 22:55, C1.2
at 23:44 UTC
December 15-17: No obviously Earth directed CMEs observed.
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 recurrent coronal hole (CH489) in the northern hemisphere was in an Earth facing position on December 16-17.
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 good. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet on December 18. On December 19-20 quiet to unsettled conditions are likely due to weak effects from CH489.
| 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.
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 detected |
Spot count | Location at midnight | Area | Classification | SDO / HMI 4K continuum image with magnetic polarity overlay |
Comment | |||
|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | STAR SDO | SWPC | STAR | Current | Previous | |||||
| 11374 | 2011.12.07 2011.12.08 |
4 | 7 | S18W50 | 0100 | CAO | HSX |
 |
 |
area: 0160 location: S17W50 |
| 11375 | 2011.12.08 | 1 | 3 | N08W57 | 0030 | HSX | HRX |
 |
 |
location: N10W57 |
| 11378 | 2011.12.11 2011.12.16 |
4 | 3 | S17W21 | 0010 | BXO | BXO |
 |
 |
area: 0000 location: S15W22 |
| 11376 | 2011.12.11 2011.12.13 |
1 | 12 | N21W04 | 0000 | AXX | BXO |
 |
 |
location: N26E06 note that SWPC has region S1378 as 11376 |
| 11377 | 2011.12.13 2011.12.14 |
9 | 11 | N12E03 | 0050 | DSO | CAO |
 |
 |
location: N14E04 |
| S1370 | 2011.12.13 | S04W27 | plage | |||||||
| S1371 | 2011.12.14 | N20W10 |
 |
plage | ||||||
| S1372 | 2011.12.15 | N17W53 | plage | |||||||
| S1373 | 2011.12.16 | 2 | S17E44 | 0000 | BXO |
 |
 |
|||
| 11380 | 2011.12.16 2011.12.17 |
1 | 4 | S20E70 | 0030 | HRX | HRX |
 |
 |
|
| 11379 | 2011.12.16 2011.12.17 |
5 | 6 | S29W22 | 0030 | CRO | BXO |
 |
 |
reversed polarities |
| S1376 | 2011.12.17 | 10 | S17E37 | 0060 | DAO |
 |
||||
| S1377 | 2011.12.17 | 1 | N08E07 | 0000 | AXX |
 |
||||
| S1378 | 2011.12.17 | 7 | N22W04 | 0020 | CRO |
 |
||||
| Total spot count: | 25 | 66 | ||||||||
| Sunspot number: | 95 | 176 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted penumbral SN: | 46 | 90 | (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10) | |||||||
| Relative sunspot number (Wolf number): | 57 | 79 | k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1) for STAR SDO | |||||||
| Month | Average measured solar flux | International sunspot number (SIDC) | Smoothed sunspot number | Average ap (3) |
|---|---|---|---|---|
| 2008.07 | 65.7 (SF minimum) | 0.5 | 2.8 (-0.4) | |
| 2008.12 | 69.2 | 0.8 | 1.7 (-) sunspot minimum |
3.25 |
| 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 | 36.9 (+3.5) | 7.79 / 8.18 |
| 2011.04 | 112.6 | 54.4 | 41.8 (+4.9) | 9.71 / 8.83 |
| 2011.05 | 95.8 | 41.6 | 47.6 (+5.8) | 9.18 / 8.94 |
| 2011.06 | 95.8 | 37.0 | (53.7 projected, +6.1) | 8.96 / 8.06 |
| 2011.07 | 94.2 | 43.9 | (60.0 projected, +6.3) | 9.14 / 8.16 |
| 2011.08 | 101.7 | 50.6 | (65.5 projected, +5.5) | 8.16 / 7.26 |
| 2011.09 | 133.8 | 78.0 | (68.8 projected, +3.3) | 12.80 / 12.27 |
| 2011.10 | 137.3 | 88.0 | (72.3 projected, +3.5) | 7.52 |
| 2011.11 | 153.5 | 96.7 | (76.6 projected, +4.3) | 4.58 |
| 2011.12 | 142.3 (1) | 57.6 (2A) / 105.1 (2B) | (82.1 projected, +5.5) | (3.53) |
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 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.
