Solar Terrestrial Activity Report

Activity chart

Last major update issued on January 19, 2013 at 02:45 UTC. Note: Updates will be irregular until January 28.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update January 1, 2013)] [Cycle 24 progress (last update January 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update January 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update January 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update January 2, 2013)]

[POES auroral activity level since October 2009 - updated October 7, 2012]
[Solar polar fields vs solar cycles - updated January 8, 2013]

Recent activity

The geomagnetic field was quiet to unsettled on January 18. Solar wind speed at SOHO ranged between 346 and 434 km/s under the influence of weak CME effects.

Solar flux measured at 20h UTC on 2.8 GHz was 115.2 (decreasing 0.1 over the last solar rotation). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.3). Three hour interval K indices: 33223223 (planetary), 22223322 (Boulder).

The background x-ray flux was at the class B2 level.

At midnight UTC the visible solar disk had 5 spotted active regions (in 2K resolution SDO images).

Region 11654 [N07W61] decayed slowly and was mostly quiet. Interestingly a small positive polarity spot emerged inside the leading penumbra creating a weak magnetic delta structure.
Region 11658 [S12W04] was quiet and stable.

Spotted regions not numbered by SWPC:
S2175 [S12W24] lost a few spots and was quiet.
S2181 [N12E27] developed and produced the only interesting event of the day, an impulsive C5.8 flare at 17:07 UTC.
New region S2184 [N24E60] emerged with a tiny spot.

Coronal mass ejections (CMEs)

January 17-18: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
January 16: An eruption near old AR 11650 close to the southwest limb was recorded as a long duration C2.2 event peaking at 19:23 UTC. The event was associated with a minor increase in proton flux levels and a partial halo CME.

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

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. Propagation on long distance northeast-southwest paths is poor to fair.


The geomagnetic field is expected to be quiet to unsettled on January 19. On January 20 there's a slight chance the CME observed on January 16 could arrive. If it does unsettled to active conditions are likely, otherwise expect quiet conditons. Quiet conditions are likely on January 21-22.

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 (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
11654 2013.01.07 18 17 9 N07W59 0460 FKO FHO


11657 2013.01.08
      S17W75           plage
11656 2013.01.09


11658 2013.01.12
3 7 3 S12W05 0090 HSX CSO  
S2173 2013.01.13       S22W14           plage
S2175 2013.01.14   4   S12W24 0000   BXO  
S2176 2013.01.15       N09W28           plage
S2177 2013.01.15       S12W57           plage
S2178 2013.01.15       S23W49           plage
11659 2013.01.16
5     N04E40 0010 BXO     spotless
S2181 2013.01.17   10 6 N12E27 0020   BXO  
S2182 2013.01.17       N16E13         plage
S2183 2013.01.17       S42W10         plage
S2184 2013.01.18   1   N24E60 0000   AXX    
Total spot count: 26 39 18  
Sunspot number: 56 89 48  (total spot count + 10 * number of spotted regions)
Weighted SN: 41 54 38  (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): 34 31 26 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
2011.10 137.3 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 58.9 (-2.8) 10.08
2012.07 133.9 66.5 (57.4 projected, -1.5) 13.90
2012.08 115.4 63.1 (58.3 projected, +0.9) 7.96
2012.09 122.9 61.5 (58.9 projected, +0.6) 8.07
2012.10 123.3 53.3 (58.3 projected, -0.6) 9.97
2012.11 121.3 61.4 (57.6 projected, -0.7) 7.08
2012.12 108.6 40.8 (56.9 projected, -0.7) 3.44
2013.01 145.0 (1) 76.3 (2A) / 131.4 (2B) / 69.7 (2C) (56.2 projected, -0.7) (4.29)

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.