Solar Terrestrial Activity Report

Last major update issued on December 31, 2011 at 06:00 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 to unsettled on December 30. Solar wind speed ranged between 334 and 473 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 141.1 (decreasing 23.0 over the last solar rotation). The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.3). Three hour interval K indices: 11101322 (planetary), 11112322 (Boulder).

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

At midnight UTC the visible solar disk had 9 spotted regions (in 2K resolution SDO images).

Region 11384 [N12W71] was quiet and stable.
Region 11386 [S16W19] decayed slowly and quietly. Note that SWPC includes region S1392 in this region.
Region 11388 [S23E29] was quiet and stable.
Region 11389 [S17E44] was quiet and stable. Note that SWPC includes region S1401 in this region.
Region 11390 [N11E44] merged with region S1398.

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. Location at midnight: S18W16
[S1401] rotated into view at the southeast limb on December 28 and developed significantly in the central and trailing spot sections on Dec.29. 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: S24E50. Flares: M1.2 at 03:09, C3.4 at 08:25, C1.6 at 10:06, C8.4 at 10:32, C1.8 at 13:41, C1.8 at 18:23 UTC.
[S1403] emerged in the northeast quadrant on December 30. Location at midnight: N24E14
[S1404] emerged in the northwest quadrant on December 30. Location at midnight: N11W08

Coronal mass ejections (CMEs)

December 28-30: 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to occasionally unsettled on December 31 - January 1 due to weak coronal hole effects, quiet conditions are likely on January 2-3.

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
11383 2011.12.18
2011.12.19
    N04W83         plage
11384 2011.12.19
2011.12.20
3 1 N12W70 0310 CHO HHX

area: 0400

11386 2011.12.22
2011.12.23
12 4 S18W18 0100 ESO AXX area: 0000

location: S16W19

SWPC includes region S1392

S1392 2011.12.23   6 S18W16 0130   HSX  
S1393 2011.12.24     N23W11           plage
S1394 2011.12.24     N26W52           plage
S1395 2011.12.25     S18W11         plage
11388 2011.12.26
2011.12.27
1 5 S23E29 0060 HSX CSO area: 0110
S1398 2011.12.26                 merged with region 11390 on Dec.30
11389 2011.12.27
2011.12.28
15 1 S23E44 0500 EKC HHX area: 0320

location: S17E44

SWPC includes region S1401

S1400 2011.12.27     N17E03           plage
S1401 2011.12.28   14 S24E50 0450   EAC beta-gamma-delta
11390 2011.12.28 8 6 N09E14 0040 CSO CRO location: N11E14

area: 0020

S1402 2011.12.29     N18W61         plage
S1403 2011.12.30   1 N24E14 0000   AXX    
S1404 2011.12.30   1 N11W08 0000   AXX    
Total spot count: 39 39  
Sunspot number: 89 129  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 74 77  (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): 53 58  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
2011.12 141.6 (1) 103.0 (2A) / 106.4 (2B) (82.1 projected, +5.5) (3.28)

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.