Solar Terrestrial Activity Report

Last major update issued on December 22, 2011 at 05:40 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 21, 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 quiet on December 21. Solar wind speed ranged between 334 and 424 km/s, still weakly under the influence of a low speed stream from CH489.

Solar flux measured at 20h UTC on 2.8 GHz was 144.5 (increasing 7.3 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.5). Three hour interval K indices: 11011222 (planetary), 12012222 (Boulder).

The background x-ray flux is at the class B8 level.

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

Region 11380 [S21E22] was quiet and stable.
Region 11381 [S18W17] was quiet and stable.
Region 11382 [S17W10] produced a number of flares and has minor polarity intermixing. A minor M class flare is possible. Flares: C3.1 at 03:12, C4.3 at 04:55, C3.6 at 06:27, C3.9 at 07:40, C2.2 at 09:09, C2.5 at 15:28 UTC
Region 11383 [N03E41] was quiet and stable.
Region 11384 [N13E52] developed further and is a compact region capable of producing M class flares. Flares: C2.0 at 06:59, C2.5 at 10:38, C2.1 at 11:05, C1.3 at 12:35, C2.0 at 13:07 UTC

Spotted regions not reported by NOAA/SWPC:
[S1378] emerged in the northern hemisphere near the central meridian on December 17. Note that SWPC considers this to be region 11376. The region developed slowly on Dec.19, then very quickly on Dec.20-21. This compact region is capable of producing M class flares. Location at midnight: N19W57. Flares: C1.5 at 00:59, C1.9 at 18:12, C1.7 at 19:06, C1.5 at 20:11, C2.0 at 22:43 UTC
[S1387] emerged in the northeast quadrant on December 20. Location at midnight: N12W03
[S1388] emerged in the southeast quadrant on December 21. Polarities are reversed. Location at midnight: S15E26
[S1389] emerged in the southeast quadrant on December 21. Location at midnight: S32E25

Coronal mass ejections (CMEs)

December 19-21: No obviously Earth directed CMEs observed.

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

No obvious coronal holes are currently in or near Earth facing positions.

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 to fair.

Forecast

The geomagnetic field is expected to be quiet on December 22-24.

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
11378 2011.12.11
2011.12.16
    S17W77           plage
11376 2011.12.11
2011.12.13
11   N20W59 0090 DSI     spotless

location: N25W45

note that SWPC has region S1378 as 11376

11377 2011.12.13
2011.12.14
    N12W54         plage
11381 2011.12.16
2011.12.18
7 14 S15W17 0070 CSO CSI location: S18W17
11380 2011.12.16
2011.12.17
  5 S21E17 0000   BXO location: S21E22
11379 2011.12.16
2011.12.17
    S29W75           plage
11382 2011.12.17
2011.12.18
17 30 S14W10 0140 DSC DSC

beta-gamma

area: 0330

location: S17W10

S1377 2011.12.17     N08W45           plage
S1378 2011.12.17   25 N19W57 0700   DKC beta-gamma
11383 2011.12.18
2011.12.19
1 1 N04E39 0020 HSX HRX location: N03E41
S1380 2011.12.18     N27W00         plage
11384 2011.12.19
2011.12.20
7 26 N14E52 0210 CAO DKC area: 0600

location: N13E52

S1383 2011.12.19     S22W21         plage
S1384 2011.12.19     N18W22         plage
S1385 2011.12.20     S03E09         plage
S1386 2011.12.20     N15E22         plage
S1387 2011.12.20   4 N12W03 0000   BXO  
S1388 2011.12.21   1 S15E26 0000   AXX    
S1389 2011.12.21   1 S32E25 0000   AXX    
Total spot count: 43 107  
Sunspot number: 93 197  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 68 140  (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): 56 89  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
2011.12 140.8 (1) 72.4 (2A) / 106.8 (2B) (82.1 projected, +5.5) (3.64)

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.