Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 28, 2012 at 04:55 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, 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 27. Solar wind speed at SOHO ranged between 270 and 362 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 106.8 (decreasing 3.8 over the last solar rotation). The Potsdam WDC planetary A index was 0 (STAR Ap - based on the mean of three hour interval ap indices: 0.3). Three hour interval K indices: 00000000 (planetary), 00001210 (Boulder).

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

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

Region 11635 [N10W43] decayed quickly and barely has rudimentary penumbra on the few remaining umbrae.
Region 11636 [N11E32] lost the trailer spot and could soon become spotless.
Region 11637 [N05E35] was quiet and stable.
New region 11638 [N11E71] rotated into view on December 26 and got its NOAA number the next day.
New region 11639 [S17E71] rotated into view on December 26 and was numbered by SWPC the next day.

Spotted regions not numbered by NOAA/SWPC:
S2131 [N20E12] lost the leader spot and gained a tiny trailing spot.

Coronal mass ejections (CMEs)

December 25-27: 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) was 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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is good to very good. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on December 28-31. 

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
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
11635 2012.12.18 21 18 9 N12W45 0120 DSI DRO beta-gamma

location: N10W43

area: 0030

S2117 2012.12.18       S13W49           plage
S2119 2012.12.20       N07W31           plage
S2123 2012.12.22       S28W59           plage
11637 2012.12.24
2012.12.26
1 2 1 N06E34 0010 AXX HRX  
11636 2012.12.24
2012.12.25
1 6   N09E30 0010 AXX BXO location: N11E32
S2127 2012.12.25       S09W40           plage
S2128 2012.12.26       S13E17         plage
11639 2012.12.26
2012.12.27
4 6 4 S16E67 0050 DSO DAO location: S17E71

area: 0120

11638 2012.12.26
2012.12.27
1 1 1 N12E67 0080 HSX HHX area: 0280

location: N11E71

S2131 2012.12.26   1   N20E12 0000   AXX  
S2132 2012.12.26       S14E47         plage
Total spot count: 28 34 15  
Sunspot number: 78 94 55  (total spot count + 10 * number of spotted regions)
Weighted SN: 43 55 36  (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): 47 33 30 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)
2011.09 133.8 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
8.81
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
2012.12 108.7 (1) 53.1 (2A) / 61.0 (2B) / 39.4 (2C) (59.3 projected, -0.7) (3.43)

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.