Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 23, 2012 at 05:15 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, 2012)] [Cycle 24 progress (last update December 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update December 1, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update December 1, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update December 7, 2012)]

[POES auroral activity level since October 2009 - updated October 7, 2012]
[Solar polar fields vs solar cycles - updated December 22, 2012]

Recent activity

The geomagnetic field was inactive on December 22. Solar wind speed at SOHO ranged between 334 and 447 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 115.3 (decreasing 6.3 over the last solar rotation). The Potsdam WDC planetary A index was 1 (STAR Ap - based on the mean of three hour interval ap indices: 0.8). Three hour interval K indices: 00000000 (planetary), 00111101 (Boulder).

The background x-ray flux was at the class B3 level.

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11633 [S07W23] added spots and has become more complex magnetically. A weak magnetic delta structure could be forming in a small penumbra in the northern part of the leading spot section, there's polarity intermixing in other parts of the region. C and minor M class flares are possible.
Region 11634 [S13W23] decayed slowly and quietly.
Region 11635 [N12E23] developed significantly and could produce M class flares. The region is compact and has significant polarity intermixing. A weak magnetic delta structure has formed in the northeastern section.

Spotted regions not numbered by NOAA/SWPC:
New region S2121 [S13E03] emerged with small spots.
New region S2122 [S12W12] emerged in what used to be the trailing part of AR 11634.
New region S2123 [S28E06] emerged with a tiny 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

A recurrent trans equatorial coronal hole (CH548) will be in an Earth facing position on December 23-24. CH548 did not cause any significant disturbance during the previous rotation.

Coronal hole map

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.


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.


The geomagnetic field is expected to be quiet on December 23-25. On December 26-27 quiet to active conditions are possible due to effects from CH548. 

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 higher resolution image) 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 (blue-green) 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
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
2K 1K
11633 2012.12.14
12 37 20 S05W27 0170 ESI ESI


location: S07W26

S2116 2012.12.14       N10W53           plage
11634 2012.12.15 7 14 3 S12W25 0060 CSO CRO

location: S13W23

11635 2012.12.18 18 39 21 N10E22 0200 ESI DAC beta-gamma-delta

area: 0450

location: N12E23

S2117 2012.12.18       S13E16           plage
S2118 2012.12.19       N13W50           plage
S2119 2012.12.20       N07E34         plage
S2120 2012.12.20       S31W48           plage
S2121 2012.12.22   2 2 S13E03 0010   BXO    
S2122 2012.12.22   6 3 S12W12 0020   CRO    
S2123 2012.12.22   1   S28E06 0000   AXX    
Total spot count: 37 99 49  
Sunspot number: 67 159 99  (total spot count + 10 * number of spotted regions)
Weighted SN: 52 115 65  (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): 40 56 54 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
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 (cycle max) 96.7 (cycle max) 61.1 (+1.2) 5.55
2011.12 141.3 73.0 63.4 (+2.3) 3.78
2012.01 132.5 58.3 65.5 (+2.1) 7.15
2012.02 106.5 32.9 66.9 (+1.4)
possible cycle 24 max
2012.03 114.7 64.3 66.8 (-0.1) 16.08
2012.04 113.0 55.2 64.6 (-2.2) 10.10
2012.05 121.5 69.0 61.7 (-2.9) 7.06
2012.06 119.6 64.5 (59.5 projected, -2.2) 10.08
2012.07 133.9 66.5 (58.8 projected, -0.7) 13.90
2012.08 115.4 63.1 (60.1 projected, +1.3) 7.96
2012.09 122.9 61.5 (61.1 projected, +1.0) 8.07
2012.10 123.3 53.3 (60.7 projected, -0.4) 9.97
2012.11 121.3 61.4 (60.0 projected, -0.7) 7.08
2012.12 108.1 (1) 41.5 (2A) / 58.4 (2B) / 42.3 (2C) (59.3 projected, -0.7) (3.83)

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 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.