Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 20, 2013 at 03:55 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 quiet on December 19. Solar wind speed at SOHO ranged between 309 and 446 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 153.4 (increasing 10.6 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 137.4. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.9). Three hour interval K indices: 11001221 (planetary), 11101211 (Boulder).

The background x-ray flux was at the class B8 level.

At the time of counting spots (see image time) spots were observed in 12 active regions in 2K resolution (SN: 252) and 9 active regions in 1K resolution (SN: 156) SDO images on the visible solar disk.

Region 11917 [S17W84] rotated partly out of view.
Region 11918 [S09W67] decayed quickly with only a few penumbra spots remaining at the end of the day.
Region 11920 [N12W61] was quiet and stable.
Region 11921 [N07W57] was quiet and stable.
Region 11925 [S07W25] was quiet and stable.
Region 11928 [S16W20] developed slowly and was mostly quiet. There's a weak magnetic delta structure in a central penumbra. C and minor M class flares are possible.
Region 11929 [S11E39] developed slowly and quietly.
Region 11930 [S10E22] gained penumbral area and lost a few spots.
Region 11931 [S14E68] rotated fully into view. Further M class flaring is possible.
C5+ flare: M3.5 at 23:19 UTC.
Region 11932 [N04E17] emerged on December 18 and was numbered by SWPC the next day.

Spotted regions not numbered by SWPC:
S2918 [S13W37] developed quickly and could produce C flares.
New region S2931 [S06W45] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

December 17-19: 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 20-23.

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
11917 2013.12.06
2013.12.07
2 2   S17W91 0180 CSO HSX

location: S17W84

11918 2013.12.08 3 3   S10W70 0010 AXX AXX

 

11920 2013.12.08
2013.12.09
2 3 2 N13W62 0060 CSO CSO

 

area: 0080

11921 2013.12.09 2 4 3 N06W57 0220 HAX CHO area: 0380
11925 2013.12.11
2013.12.13
  8 4 S07W24 0023   BXO  
11926 2013.12.14       N10W72           plage
S2918 2013.12.14   16 7 S13W37 0120   DAI beta-gamma
S2919 2013.12.14       N33W57           plage
S2921 2013.12.15       N21W32           plage
11928 2013.12.16
2013.12.17
24 53 30 S16W19 0360 EKC EKC beta-gamma-delta

area: 0750

11929 2013.12.16
2013.12.18
2 12 6 S11E40 0010 BXO CRI area: 0050
S2924 2013.12.16       N10W38           plage
S2925 2013.12.16       N08W29           plage
11930 2013.12.17
2013.12.18
10 21 8 S11E22 0090 DAI DAO

area: 0160

11931 2013.12.18 1 7 4 S15E62 0210 HAX FHO beta-gamma

area: 0400

11932 2013.12.18
2013.12.19
2 2 2 N04E17 0010 AXX DRO area: 0020
S2930 2013.12.18       S37W23         plage
S2931 2013.12.19   1   S06W45 0002   AXX    
Total spot count: 48 132 66  
Sunspot number: 138 252 156  (total spot count + 10 * number of spotted regions)
Weighted SN: 83 188 117  (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): 83 88 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
2013.12 155.0 (1) 76.0 (2A) / 124.1 (2B) / 81.3 (2C) (61.7 projected, -1.3) (5.4)

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.