Solar Terrestrial Activity Report

Last major update issued on December 30, 2011 at 06:10 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 30, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2116 [October-November 2011] - 2117 [November-December 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on December 29. Solar wind speed ranged between 318 and 508 km/s. No obvious solar wind shocks were observed and the solar wind disturbance was likely the combined effects of weak CMEs and a high speed stream from CH490.

Solar flux measured at 20h UTC on 2.8 GHz was 147.1 (decreasing 10.2 over the last solar rotation). The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.9). Three hour interval K indices: 12331111 (planetary), 12342222 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight UTC the visible solar disk had 12 spotted regions (in 2K resolution SDO images).

Region 11380 [S22W86] was quiet as it rotated to the southwest limb.
Region 11383 [N04W67] decayed slowly and quietly.
Region 11384 [N12W58] decayed slowly and quietly.
Region 11386 [S16W07] decayed slowly and quietly. Note that SWPC includes regions S1392 and S1395 in this region.
Region 11388 [S23E42] added a few small spots and was quiet.
Region 11389 [S17E57] was quiet and stable. Note that SWPC includes region S1401 in this region.
Region 11390 [N10E33] decayed losing the leader spots. SWPC includes region S1398 in this region.

Spotted regions not reported (or interpreted differently) by NOAA/SWPC:
[S1392] rotated into view at the southeast limb on December 23. Location at midnight: S18W03
[S1395] emerged in the southeast quadrant on December 25. Location at midnight: S18E02
[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: N11E27.
[S1401] rotated into view at the southeast limb on December 28 and developed significantly in the central and trailing spot sections on Dec.29. At midnight 2 magnetic delta structures were observed. Note that SWPC includes this region in AR 11389. Further M class flaring is likely. Location at midnight: S24E64. Flares: C3.0 at 04:05, C3.0 at 06:21, C7.3 at 07:18, C5.4 at 08:48, C1.5 at 09:49, M1.9 at 13:50, C2.8 at 16:21, C2.9 at 17:32, C2.3 at 19:25, C2.3 at 20:32, C2.5 at 21:01, M2.0 at 21:51 UTC.
[S1402] emerged in the northwest quadrant on December 29. Location at midnight: N18W48

Coronal mass ejections (CMEs)

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 28-29: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

Coronal holes

Coronal hole history (since October 2002)
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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to occasionally unsettled on December 30 - January 1 due to weak CME and coronal hole effects.

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
11380 2011.12.16
2011.12.17
  2 S22W86 0180   CAO this is AR 11387 to SWPC
11383 2011.12.18
2011.12.19
1 1 N04W68 0005 HRX AXX  
11384 2011.12.19
2011.12.20
5 1 N12W55 0340 CKO HHX

 

11385 2011.12.21
2011.12.23
    S32W81           plage
11386 2011.12.22
2011.12.23
9 7 S17W05 0140 DSI BXO area: 0010

location: S16W07

SWPC includes regions S1392, S1395

S1392 2011.12.23   7 S18W03 0160   CSO  
S1393 2011.12.24     N23E02           plage
S1394 2011.12.24     N26W39           plage
S1395 2011.12.25   3 S18E02 0000   BXO  
11387 2011.12.25 5   S19W83 0170 DAO       see region 11380
11388 2011.12.26
2011.12.27
1 5 S23E41 0070 HSX CSO location: S23E42
S1398 2011.12.26   5 N11E27 0020   CRO  
11389 2011.12.27
2011.12.28
8 1 S23E58 0290 EKI HHX area: 0320

location: S17E57

SWPC includes region S1401

S1400 2011.12.27     N17E16           plage
S1401 2011.12.28   18 S24E64 0450   EAC beta-gamma-delta
11390 2011.12.28 6 4 N08E29 0010 CAO AXX SWPC includes region S1398
S1402 2011.12.29   2 N18W48 0000   AXX    
Total spot count: 35 56  
Sunspot number: 105 176  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 78 99  (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): 63 79  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
2011.12 141.6 (1) 100.1 (2A) / 107.0 (2B) (82.1 projected, +5.5) (3.22)

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.