Solar Terrestrial Activity Report

Last major update issued on December 26, 2011 at 05:45 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 23, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2115 [September-October 2011] - 2116 [October-November 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was very quiet on December 25. Solar wind speed ranged between 343 and 419 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 144.3 (increasing 6.7 over the last solar rotation). The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.6). Three hour interval K indices: 11100001 (planetary), 11101031 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight UTC the visible solar disk had 10 spotted regions (in 2K resolution SDO images).

Region 11380 [S21W28] developed quickly and currently has a very messy magnetic layout. SWPC decided to renumber the region as 11387. There's a small magnetic delta structure in a small penumbra in the northwestern part of the region. Further M class flares are possible. Flares: C1.6 at 04:52, C5.5 at 08:55, C8.4 at 11:26, C2.2 at 17:01, M4.0/1N at 18:16 (associated with a moderate type II and a strong type IV radio sweep, a CME and a proton flux enhancement), C7.7 at 20:29 UTC.
Region 11382 [S18W66] decayed slowly and was quiet.
Region 11383 [N04W13] decayed slowly and quietly.
Region 11384 [N13W03] decayed slowly and quietly.
Region 11385 [S30W25] decayed slowly and quietly.
Region 11386 [S16E45] was quiet and stable. Note that SWPC includes regions S1392 and S1395 in this region.

Spotted regions not reported (or interpreted differently) by NOAA/SWPC:
[S1392] rotated into view at the southeast limb on December 23. Location at midnight: S18E49
[S1393] emerged in the northeast quadrant on December 24. Location at midnight: N20E54
[S1394] emerged in the northeast quadrant on December 24. Location at midnight: N21E03
[S1395] emerged in the southeast quadrant on December 25. Location at midnight: S18E58

Coronal mass ejections (CMEs)

December 23-24: No obviously Earth directed CMEs observed.
December 25: A partial halo CME was observed early in the day in LASCO images in association with a filament eruption in the central northern hemisphere. There's a 20-30% chance of a flank impact from this CME sometime on December 28. A CME was observed in STEREO images after the M4 event in region 11380. This CME could reach Earth sometime between late on December 27 and late on December 28 and cause unsettled to major storm conditions.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

An extension (CH490) of the southern polar coronal hole could rotate into an Earth facing position on December 26-27.

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

Forecast

The geomagnetic field is expected to be quiet on December 26-27. Quiet to major storm conditions are possible on December 28-29 due to CME effects. A high speed stream from CH490 could cause some unsettled and active intervals on December 29-31.

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
11381 2011.12.16
2011.12.18
2   S18W68 0100 CSO       plage

location: S18W70

SWPC has a data consistency problem with regions 11381/11382

11380 2011.12.16
2011.12.17
  29 S21W39 0200   DSI gamma-delta

location: S21W28

SWPC lost track of this region and assigned a new number 11387

11382 2011.12.17
2011.12.18
  4 S18W61 0180 CSO CSO

location: S18W66

SWPC thinks this is region 11381

11383 2011.12.18
2011.12.19
1 1 N03W14 0010 HSX AXX location: N04W13
S1380 2011.12.18     N27W42           plage
11384 2011.12.19
2011.12.20
7 11 N13W00 0330 DHI EHO area: 0500

location: N13W03

S1385 2011.12.20     S03W43           plage
S1386 2011.12.20     N20W19           plage
S1387 2011.12.20     N12W42           plage
S1388 2011.12.21     S15W26           plage
11385 2011.12.21
2011.12.23
  5 S32W30 0005   BXO  
11386 2011.12.22
2011.12.23
3 4 S18E49 0120 DSO CSO area: 0060

location: S16E45

SWPC includes regions S1392, S1395

S1392 2011.12.23   9 S18E49 0070   CSO  
S1393 2011.12.24   4 N20E54 0000   BXO  
S1394 2011.12.24   2 N21E03 0000   AXX  
S1395 2011.12.25   6 S18E58 0010   BXO    
11387 2011.12.25 3   S22W28 0030 DAO       see region 11380
Total spot count: 16 75  
Sunspot number: 66 175  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 51 105  (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 79  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
2011.12 141.1 (1) 84.7 (2A) / 105.1 (2B) (82.1 projected, +5.5) (3.30)

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.