Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 22, 2013 at 05:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update December 1, 2013)] [Cycle 24 progress (last update December 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update December 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update December 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update December 1, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated December 16, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was very quiet on December 21. Solar wind speed at SOHO ranged between 308 and 405 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 144.2 (increasing 17.1 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 138.1. The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.5). Three hour interval K indices: 11110010 (planetary), 11212221 (Boulder).

The background x-ray flux was at the class B7 level.

At the time of counting spots (see image time) spots were observed in 11 active regions in 2K resolution (SN: 260) and 10 active regions in 1K resolution (SN: 176) SDO images on the visible solar disk.

Region 11920 [N13W86] decayed slowly and quietly.
Region 11921 [N07W83] was quiet and stable.
Region 11925 [S07W60] was quiet and stable.
Region 11928 [S16W48] still has a small magnetic delta structure centrally and significant polarity intermixing otherwise. C and M class flares are likely.
C5+ flares: C9.2/1F at 10:36, C7.5 at 19:29 UTC.
Region 11929 [S11E11] was quiet and stable.
Region 11930 [S09W05] was quiet and stable.
Region 11931 [S14E42] has a positive polarity area embedded within the trailing negative polarity. While the region was mostly quiet, there is a chance of C and M class flaring.

Region 11933 [S12W64] decayed slowly and quietly.

Spotted regions not numbered by SWPC:
New region S2936 [N07W23] emerged with penumbra spots.
New region S2937 [N17W23] emerged with several spots.
New region S2938 [S33W41] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

December 19-21: 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

No obvious coronal holes are currently in or near Earth facing positions.

Coronal hole map

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 to fair.

Forecast

The geomagnetic field is expected to be quiet on December 22-24.

Coronal holes (1) Coronal mass ejection (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 2K resolution) Compare to the previous day's image. 0.5K image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue 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
2K 1K
11920 2013.12.08
2013.12.09
1 1 1 N13W88 0030 HAX HAX

 

11921 2013.12.09 2 2 2 N07W85 0180 HAX HSX area: 0340
11925 2013.12.11
2013.12.13
  3 1 S07W54 0009   BXO  
11933 2013.12.14
2013.12.20
3 8 3 S13W65 0060 DAO DSO  

area: 0120

S2921 2013.12.15       N21W58           plage
11928 2013.12.16
2013.12.17
28 64 40 S17W47 0460 EKC EKC beta-gamma-delta

area: 0730

11929 2013.12.16
2013.12.18
3 17 6 S12E11 0010 AXX BXO area: 0030
S2925 2013.12.16       N08W55           plage
11930 2013.12.17
2013.12.18
7 22 9 S11W05 0090 DAI DSO

area: 0170

11931 2013.12.18 2 24 11 S15E36 0220 HSX FHO beta-gamma

area: 0470

location: S14E42

11932 2013.12.18
2013.12.19
      N04W11         plage
11934 2013.12.20 5     S15E53 0140 CAO       the spots are part of AR 11931
S2935 2013.12.20       N17W05         plage
S2936 2013.12.21   2 1 N07W23 0008   BXO    
S2937 2013.12.21   6 2 N17E02 0030   CRO    
S2938 2013.12.21   1   S33W41 0002   AXX    
Total spot count: 51 150 76  
Sunspot number: 131 260 176  (total spot count + 10 * number of spotted regions)
Weighted SN: 91 193 119  (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): 79 91 97 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2011.11 153.5 (cycle peak) 96.7 (cycle peak) 61.1 (+1.2) 5.55
2012.02 106.5 32.9 66.9 (+1.4)
possible cycle 24 max
8.81
2012.09 122.9 61.4 58.1 (-0.1) 8.07
2012.10 123.3 53.3 58.6 (+0.5) 9.97
2012.11 121.3 61.8 59.7 (+1.1) 7.08
2012.12 108.6 40.8 59.6 (-0.1) 3.44
2013.01 127.1 62.9 58.7 (-0.9) 4.69
2013.02 104.3 38.0 58.4 (-0.3) 6.11
2013.03 111.3 57.9 57.5 (-0.9) 10.56
2013.04 124.8 72.4 57.9 (+0.4) 5.40
2013.05 131.4 78.7 59.9 (+2.0) 9.73
2013.06 110.1 52.5 (62.2 projected, +2.3) 12.60
2013.07 115.5 57.0 (63.9 projected, +1.7) 9.47
2013.08 114.6 66.0 (64.8 projected, +0.9) 8.27
2013.09 102.6 36.9 (65.6 projected, +0.8) 5.23
2013.10  132.1 85.6 (64.9 projected, -0.7) 7.71
2013.11  148.3 77.6 (63.0 projected, -1.9) 5.68
2013.12 154.2 (1) 84.7 (2A) / 125.0 (2B) / 83.7 (2C) (61.7 projected, -1.3) (5.2)

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) Boulder SN current month average to date. 2C) STAR SDO 1K Wolf number 30 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on the 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.