Last major update issued on December 29, 2011 at 06:25 UTC.
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Annotated geomagnetic activity charts - Carrington rotation 2116 [October-November 2011] - 2117 [November-December 2011] NEW
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The geomagnetic field was quiet on December 28. Solar wind speed ranged between 275 and 329 km/s. A weak disturbance (source unknown) was observed arriving at ACE near 09:50 UTC and caused a minor increase in geomagnetic activity for the remainder of the day.
Solar flux measured at 20h UTC on 2.8 GHz was 144.8 (decreasing 7.6 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.8). Three hour interval K indices: 00011211 (planetary), 10012321 (Boulder).
The background x-ray flux is at the class B6 level.
At midnight UTC the visible solar disk had 11 spotted regions (in 2K resolution SDO images).
Region 11380 [S21W72] decayed quickly, particularly in the trailing
spot section. There's still significant polarity intermixing and a minor M class
flare is possible. Note that SWPC has this as
region 11387. Flares: C2.3 at 00:30, C6.4 at
Region 11383 [N05W53] developed slowly and was quiet.
Region 11384 [N13W42] added several small spots and remains capable of producing an M class flare. Flare: C2.3 at 21:07 UTC.
Region 11386 [S16E06] decayed slowly. Note that SWPC includes regions S1392 and S1395 in this region. Flare: C4.0 at 20:31 UTC.
Region 11388 [S23E56] was quiet and stable.
New region 11389 [S18E70] rotated into view at the southeast limb on December 27 and got an SWPC number the next day.
New region 11390 [N09E45] emerged in the northeast quadrant on December 28.
Spotted regions not reported (or interpreted differently) by NOAA/SWPC:
[S1392] rotated into view at the southeast limb on December 23. Location at midnight: S18E10
[S1395] emerged in the southeast quadrant on December 25. Location at midnight: S18E14
[S1398] emerged in the northeast quadrant on December 26, became spotless the next day and reemerged with several spots on Dec.28. Location at midnight: N10E41.
[S1401] rotated into view at the southeast limb on December 28. Note that SWPC includes this region in AR 11389. M flares are possible. Location at midnight: S24E75. Flares: C2.1 at 02:08, C4.5 at 03:50, C2.6 at 05:28, C7.2/1F at 14:25, C6.2 at 21:29 UTC.
December 26: At least a partial halo CME was observed after a filament
eruption across the central meridian near region 11384. This CME could reach
Earth on December 29.
December 27: At least a partial halo CME was associated with the C8 flare in region 11386 early in the day. This CME is fairly slow and could reach Earth on December 30.
December 28: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A large extension (CH490) of the southern polar coronal hole was in a potentially geoeffective position on December 26-29.
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 to good. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to active on December 29-31 due to CME and coronal hole effects, occasional minor storm intervals are possible.
|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 magnetic polarity overlay
SWPC lost track of this region and assigned a new number 11387.
SWPC includes regions S1392, S1395
|11387||2011.12.25||14||S21W70||0290||DKI||see region 11380|
SWPC includes region S1401
|Total spot count:||52||79|
|Sunspot number:||122||189||(total spot count + 10 * number of spotted regions)|
|Weighted penumbral SN:||87||122||(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):||73||85||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
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|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||141.4 (1)||96.7 (2A) / 107.1 (2B)||(82.1 projected, +5.5)||(3.08)|
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.