Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 20, 2013 at 03:50 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 to unsettled on December 20. Solar wind speed at SOHO ranged between 337 and 418 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 149.2 (increasing 13.6 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 137.8. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 13010111 (planetary), 13121211 (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 11 active regions in 2K resolution (SN: 289) and 9 active regions in 1K resolution (SN: 176) SDO images on the visible solar disk.

Region 11920 [N13W76] decayed slowly and quietly.
Region 11921 [N07W68] decayed slowly and quietly.
Region 11925 [S07W39] was quiet and stable.
Region 11928 [S16W33] developed slowly and has an elongated magnetic delta structure in a central penumbra. C and M class flares are likely.
C5+ flares: C8.5 at 15:33, C5.4 at 16:30 UTC.
Region 11929 [S12E26] developed slowly in the leading polarity with decay observed in the trailing polarity area.
Region 11930 [S09E07] developed slowly and quietly.
Region 11931 [S14E56] has a positive polarity area embedded within the trailing negative polarity. This significant polarity intermixing could cause further M class flaring.
C5+ flare: M1.6 at 11:57 UTC.
Region 11932 [N03E05] decayed slowly and quietly.
New region 11933 [S12W52] was first observed with spots on December 14. New flux emerged on December 19 and the region matured quickly on December 20.

Spotted regions not numbered by SWPC:
New region S2934 [S25W76] emerged with a penumbra spot early in the day.
New region S2935 [N17E08] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

December 18-20: 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 21-23.

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
11918 2013.12.08       S10W84        

plage

11920 2013.12.08
2013.12.09
1 1 1 N13W75 0050 HAX HAX

 

11921 2013.12.09 2 3 2 N07W71 0200 HAX CSO area: 0340
11925 2013.12.11
2013.12.13
  3 1 S07W39 0009   BXO  
11926 2013.12.14       N10W86           plage
11933 2013.12.14
2013.12.20
4 17 3 S13W53 0040 CSO DSO beta-gamma

area: 0150

S2921 2013.12.15       N21W45           plage
11928 2013.12.16
2013.12.17
18 84 45 S17W32 0400 EKC EKC beta-gamma-delta

area: 0800

11929 2013.12.16
2013.12.18
5 24 10 S12E25 0010 BXO CRI area: 0050
S2924 2013.12.16       N10W51           plage
S2925 2013.12.16       N08W42           plage
11930 2013.12.17
2013.12.18
12 27 15 S11E08 0090 DAI DSI

area: 0200

11931 2013.12.18 1 17 8 S15E48 0190 HAX FHO beta-gamma

area: 0450

11932 2013.12.18
2013.12.19
1 1 1 N04E04 0010 AXX AXX area: 0003
S2931 2013.12.19       S06W58         plage
11934 2013.12.20 3     S15E65 0080 CAO       the spots are part of AR 11931
S2934 2013.12.20   1   S25W76 0003   AXX    
S2935 2013.12.20   1   N17E08 0002   AXX    
Total spot count: 47 179 86  
Sunspot number: 137 289 176  (total spot count + 10 * number of spotted regions)
Weighted SN: 87 222 129  (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): 82 101 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
2013.12 154.7 (1) 80.5 (2A) / 124.7 (2B) / 82.4 (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.