Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 23, 2013 at 05:10 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 22. Solar wind speed at SOHO ranged between 280 and 386 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 137.9 (increasing 18.8 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 138.3. The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.9). Three hour interval K indices: 11010111 (planetary), 01001211 (Boulder).

The background x-ray flux was at the class C1 level.

At the time of counting spots (see image time) spots were observed in 12 active regions in 2K resolution (SN: 274) and 9 active regions in 1K resolution (SN: 160) SDO images on the visible solar disk.

Region 11928 [S16W61] has developed several magnetic delta structures centrally and is likely to continue producing C and M class flares. C5+ flares: C5.1 at 03:47, M1.9 at 08:11, M1.1 at 08:37, M3.3/1N at 15:12, C8.8 at 19:09, C6.1 at 20:34, M1.6 at 22:08, C8.2 at 22:44, M1.3 at 00:03 (on Dec.23) UTC.
Region 11929 [S12W02] was quiet and stable.
Region 11930 [S08W20] decayed slowly and quietly.
Region 11931 [S14E31] developed in the trailing spot section with positive polarity flux still emerging within the predominantly negative polarity area. Further M class flares are possible.
C5+ flares: C6.4/1F at 09:32, M1.6/1F at 14:38 UTC.
Region 11932 [N06W25] reemerged with 2 spots.
Region 11933 [S11W82] decayed slowly and rotated to the southwest limb.

Spotted regions not numbered by SWPC:
S2937 [N17W18] decayed slowly and quietly.
New region S2939 [S17E80] rotated into view.
C5+ flare: C6.1 at 19:25 UTC.
New region S2940 [S05E63] emerged with a few spots.
New region S2941 [N15E51] emerged with penumbra spots.
New region S2942 [S10W33] emerged with a penumbra spot.
New region S2943 [N09E35] emerged with a penumbra spot

Coronal mass ejections (CMEs)

December 20-22: 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on December 23-25.

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
11921 2013.12.09 1     N07W94 0060 HSX     rotated out of view
11925 2013.12.11
2013.12.13
      S07W69         plage
11933 2013.12.14
2013.12.20
1 2 1 S13W82 0040 HSX AXX area: 0020
11928 2013.12.16
2013.12.17
22 45 24 S17W61 0380 EKC FKC beta-gamma-delta

area: 0800

11929 2013.12.16
2013.12.18
2 18 4 S13W04 0010 BXO BXO area: 0025
11930 2013.12.17
2013.12.18
5 20 10 S11W19 0060 DSO CSO

area: 0120

11931 2013.12.18 1 51 22 S15E21 0170 HSX FHC beta-gamma

area: 0600

location: S14E31

11932 2013.12.18
2013.12.19
  2 2 N04W26 0025   CRO   location: N06W25
11934 2013.12.20 9     S15E40 0160 DAC       the spots are magnetically part of AR 11931
S2935 2013.12.20       N17W18           plage
S2936 2013.12.21       N07W36         plage
S2937 2013.12.21   5 4 N17W18 0022   BXO  
S2938 2013.12.21       S33W54         plage
S2939 2013.12.22   3 2 S17E80 0035   CRO    
S2940 2013.12.22   4 1 S05E63 0025   CRO    
S2941 2013.12.22   2   N15E51 0008   BXO    
S2942 2013.12.22   1   S10W33 0001   AXX    
S2943 2013.12.22   1   N09E35 0001   AXX    
Total spot count: 41 154 70  
Sunspot number: 111 274 160  (total spot count + 10 * number of spotted regions)
Weighted SN: 76 187 103  (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): 67 96 88 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
2013.12 153.5 (1) 88.3 (2A) / 124.4 (2B) / 84.1 (2C) (61.7 projected, -1.3) (5.3)

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.