Solar Terrestrial Activity Report

Last major update issued on January 1, 2012 at 07:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update December 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update December 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update December 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update December 2, 2011)]

[POES auroral activity level since October 2009 - updated December 30, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2116 [October-November 2011] - 2117 [November-December 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on December 31. Solar wind speed ranged between 344 and 408 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 132.9 (decreasing 30.7 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 11120112 (planetary), 11121221 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 8 spotted regions (in 2K resolution SDO images).

Region 11384 [N12W85] was quiet and stable.
Region 11386 [S16W32] decayed slowly and was mostly quiet. Note that SWPC includes region S1392 in this region. Flare: C1.2 at 17:31 UTC
Region 11388 [S23E17] was quiet and stable.
Region 11389 [S16E31] added a few small spots and was quiet. Note that SWPC includes region S1401 in this region.
Region 11390 [N12W03] decayed slowly and quietly.

Spotted regions not reported (or interpreted differently) by NOAA/SWPC:
[S1392] rotated into view at the southeast limb on December 23, slow decay was observed on Dec.30-31. Location at midnight: S18W28
[S1401] rotated into view at the southeast limb on December 28 and developed significantly in the central and trailing spot sections on Dec.29-31. The region has a magnetic delta structure and could produce further M class flares. Note that SWPC includes this region in AR 11389. Location at midnight: S23E37. Flares: M2.4 at 13:15, M1.5/1F at 16:26 UTC.
[S1405] emerged in the northeast quadrant on December 31. Location at midnight: N15E14

Coronal mass ejections (CMEs)

December 29-31: 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 large extension (CH490) of the southern polar coronal hole was in a potentially geoeffective position on December 26-29. A recurrent trans equatorial coronal hole (CH491) will likely rotate into an Earth facing position on January 4-5.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, 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 the new method, the extent and intensity of both holes 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. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on January 1-5.

Coronal holes (1) Coronal mass ejections (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

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
11384 2011.12.19
2011.12.20
1 1 N11W83 0250 HHX HHX

area: 0360

11386 2011.12.22
2011.12.23
3 2 S18W32 0070 DSO AXX area: 0000

location: S16W32

SWPC includes region S1392

S1392 2011.12.23   4 S18W28 0090   HSX  
S1393 2011.12.24     N23W24           plage
11388 2011.12.26
2011.12.27
1 9 S24E15 0060 HSX CSO area: 0110

location: S23E17

11389 2011.12.27
2011.12.28
9 5 S23E31 0400 EKC CHO area: 0300

location: S16E31

SWPC includes region S1401

S1400 2011.12.27     N17W10           plage
S1401 2011.12.28   27 S23E37 0600   EKC beta-gamma-delta
11390 2011.12.28 4 6 N09W00 0010 BXO BXO location: N12W03
S1403 2011.12.30     N24E01         plage
S1404 2011.12.30     N11W21         plage
S1405 2011.12.31   2 N15E14 0000   AXX    
Total spot count: 18 56  
Sunspot number: 68 136  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 48 96  (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): 41 61  k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1) for STAR SDO

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2010.10 81.6 23.5 23.2 (+3.6) 6.07 / 6.27
2010.11 82.5 21.5 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 31.0 (+2.2) 4.32 / 5.51
2011.02 94.6 29.4 33.4 (+2.4) 5.41 / 6.44
2011.03 115.0 56.2 36.9 (+3.5) 7.79 / 8.18
2011.04 112.6 54.4 41.8 (+4.9) 9.71 / 8.83
2011.05 95.8 41.6 47.6 (+5.8) 9.18 / 8.94
2011.06 95.8 37.0 (53.7 projected, +6.1) 8.96 / 8.06
2011.07 94.2 43.9 (60.0 projected, +6.3) 9.14 / 8.16
2011.08 101.7 50.6 (65.5 projected, +5.5) 8.16 / 7.26
2011.09 133.8 78.0 (68.8 projected, +3.3) 12.80 / 12.27
2011.10 137.3 88.0 (72.3 projected, +3.5) 7.52
2011.11  153.5 96.7 (76.6 projected, +4.3) 4.58
2011.12 141.3 (1) 105.4 (2A/2B) (82.1 projected, +5.5) (3.32)

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) Month average to date.
3) Running average based on the preliminary daily SWPC ap indices. Values in red are based on the official NGDC 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.