Solar Terrestrial Activity Report

Last major update issued on December 20, 2011 at 05:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update December 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update December 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update December 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update December 2, 2011)]

[POES auroral activity level since October 2009 - updated December 19, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2115 [September-October 2011] - 2116 [October-November 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on December 19. Solar wind speed ranged between 284 and 436 km/s under the influence of a low speed stream from CH489.

Solar flux measured at 20h UTC on 2.8 GHz was 128.2 (decreasing 14.2 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.8). Three hour interval K indices: 11101232 (planetary), 12111232 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 13 spotted regions (in 2K resolution SDO images).

Region 11374 [S19W79] was quiet and stable.
Region 11376 [N21W25] decayed slowly and quietly.
Region 11377 [N12W26] decayed slowly and quietly.
Region 11379 [S29W47] decayed slowly and quietly.
Region 11380 [S21E47] added several trailing spots while the leader spots lost the rudimentary penumbra.
Region 11381 [S18E10] decayed slowly and quietly.
Region 11382 [S18E17] developed further and could produce C flares and maybe a minor M class flare.
New region 11383 [N03E69] rotated into view at the northeast limb on December 18 and was numbered the next day by SWPC.

Spotted regions not reported by NOAA/SWPC:
[S1378] emerged in the northern hemisphere near the central meridian on December 17. Note that SWPC considers this to be region 11376. The region developed slowly on Dec.19, the current magnetic layout suggests two narrowly spaced small regions. Location at midnight: N19W32
[S1380] emerged in the northeast quadrant on December 18. Location at midnight: N15E26
[S1382] rotated into view at the northeast limb on December 19. Location at midnight: N12E80
[S1383] emerged in the southeast quadrant on December 19. Location at midnight: S22E07
[S1384] emerged in the northeast quadrant on December 19. Location at midnight: N17E03

Coronal mass ejections (CMEs)

December 17-19: No obviously Earth directed CMEs observed.

Coronal holes

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.

Propagation

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.

Forecast

The geomagnetic field is expected to be mostly quiet on December 20, weakly under the influence of CH489. Quiet conditions are likely on December 21-23.

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.

Active solar regions

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
1 1 S18W76 0070 HSX HSX

area: 0130

location: S19W79

11375 2011.12.08 1   N08W83 0040 HSX     spotless
11378 2011.12.11
2011.12.16
    S17W49         plage
11376 2011.12.11
2011.12.13
7 6 N19W31 0020 CRO AXX location: N21W25

note that SWPC has region S1378 as 11376

11377 2011.12.13
2011.12.14
3 4 N13W24 0020 CRO BXO location: N12W26

area: 0005

S1370 2011.12.13     S04W53           plage
S1371 2011.12.14     N20W36           plage
11381 2011.12.16
2011.12.18
9 11 S18E10 0080 DAI DAO location: S16E24

area: 0170

11380 2011.12.16
2011.12.17
6 9 S20E43 0030 CAO BXO location: S21E47
11379 2011.12.16
2011.12.17
3 2 S29W47 0020 CRO BXO reversed polarities

area: 0000

11382 2011.12.17
2011.12.18
12 26 S18E18 0100 DAI DSI

area: 0330

S1377 2011.12.17     N08W19           plage
S1378 2011.12.17   12 N19W32 0020   BXO probably two BXO regions
11383 2011.12.18
2011.12.19
1 1 N04E68 0020 HSX HSX location: N03E68
S1380 2011.12.18   3 N15E26 0000   AXX  
S1381 2011.12.18     N11W43         plage
S1382 2011.12.19   5 N12E80 0040   DRO    
S1383 2011.12.19   4 S22E07 0000   BXO    
S1384 2011.12.19   1 N17E03 0000   AXX    
Total spot count: 43 85  
Sunspot number: 133 215  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 82 108  (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): 80 97  k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1) for STAR SDO

Monthly solar cycle data

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
2011.12 140.8 (1) 65.2 (2A) / 106.4 (2B) (82.1 projected, +5.5) (3.55)

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.