Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 24, 2013 at 05:05 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 23. Solar wind speed at SOHO ranged between 272 and 342 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 136.1 (increasing 20.6 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 138.6. The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.0). Three hour interval K indices: 11101011 (planetary), 01001111 (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: 243) and 10 active regions in 1K resolution (SN: 156) SDO images on the visible solar disk.

Region 11928 [S16W75] decayed in the trailing and central spot sections which caused a reduction in flare frequency and intensity during the latter half of the day. Further M class flares are possible. C5+ flares: C7.9 at 07:58, M1.6/1N at 09:06, C5.3 at 15:53 UTC.
Region 11929 [S12W15] was quiet and stable.
Region 11930 [S09W32] developed in the trailing spot section and was quiet.
Region 11931 [S14E18] was quiet despite continued growth in the trailing spot section. M class flaring is possible.

Region 11932 [N07W39] was quiet and stable.
New region 11935 [S05E49] emerged on December 22 and was numbered the next day by SWPC.
New region 11936 [S18E71] rotated into view on December 22 and got its NOAA number the following day. The region has polarity intermixing, and even if the spots are small, further C class events are likely.
C5+ flare: C8.4 at 17:28 UTC.

Spotted regions not numbered by SWPC:
S2937 [N18W37] decayed slowly and quietly.
S2943 [N10E26] was quiet and stable.
New region S2944 [S06E09] emerged to the north of AR 11931.
New region S2945 [N29E23] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

December 21-23: 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 24-26.

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
11925 2013.12.11
2013.12.13
      S07W84           plage
11928 2013.12.16
2013.12.17
13 17 10 S16W74 0330 EKC FKC beta-gamma

area: 0500

11929 2013.12.16
2013.12.18
3 7 1 S12W16 0010 BXO BXO  
11930 2013.12.17
2013.12.18
6 17 9 S10W32 0080 DAO DSI

area: 0140

11931 2013.12.18 1 59 22 S14E08 0190 HAX FHC beta-gamma

area: 0680

location: S14E31

11932 2013.12.18
2013.12.19
  2 1 N04W41 0011   BXO location: N07W39
11934 2013.12.20 12     S16E27 0230 DAO       the spots are magnetically part of AR 11931
S2935 2013.12.20       N17W31           plage
S2936 2013.12.21       N07W49           plage
S2937 2013.12.21   5 1 N18W32 0015   BXO  
11936 2013.12.22
2013.12.23
2 12 5 S17E71 0010 BXO DAI beta-gamma

area: 0100

11935 2013.12.22
2013.12.23
1 3 2 S05E49 0010 BXO CRO area: 0030
S2941 2013.12.22       N15E38         plage
S2942 2013.12.22       S10W48         plage
S2943 2013.12.22   1 1 N10E26 0004   AXX  
S2944 2013.12.23   9 4 S06E09 0030   BXO    
S2945 2013.12.23   1   N29E23 0003   AXX    
Total spot count: 38 133 56  
Sunspot number: 108 243 156  (total spot count + 10 * number of spotted regions)
Weighted SN: 63 166 89  (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): 65 85 86 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
2013.12 152.7 (1) 91.7 (2A) / 123.7 (2B) / 84.9 (2C) (61.7 projected, -1.3) (5.1)

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.