Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 18, 2012 at 04:05 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 9, 2012]

Recent activity

The geomagnetic field was quiet to active on December 17. Solar wind speed at SOHO ranged between 383 and 541 km/s under the influence of a high speed coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 115.0 (decreasing 26.2 over the last solar rotation). The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 10.8). Three hour interval K indices: 23343211 (planetary), 23344210 (Boulder).

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

At midnight UTC the visible solar disk had 4 spotted active regions (in 2K resolution SDO images).

Region 11631 [N20W75] decayed slowly and quietly.
Region 11633 [S07E41] gained spots and was mostly quiet. The region has minor polarity intermixing and could produce an M class flare.
Region 11634 [S13E44] gained tiny trailer spots.

Spotted regions not numbered by NOAA/SWPC:
S2116 [N08E07] was quiet and stable.

An active region is at the northeast limb and will rotate into view today. The region could produce M class flares.

Coronal mass ejections (CMEs)

December 15-17: 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

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

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

Forecast

The geomagnetic field is expected to be quiet with a chance of unsettled intervals on December 18-19 and quiet on December 20-21. 

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
11629 2012.12.08 1     N11W88 0080 HSX       same as AR 11628, rotated out of view
S2105 2012.12.10       S27W52           plage
S2106 2012.12.10       S21W38           plage
S2107 2012.12.10       N15W37         plage
11631 2012.12.11
2012.12.12
10 7 4 N23W75 0140 DSI ESO

area: 0200

location: N20W75

11632 2012.12.12 6     N19W84 0050 CAO     rotated out of view

location: N17W85

S2112 2012.12.13       N14W28           plage
S2113 2012.12.13       S13W41           plage
11633 2012.12.14
2012.12.15
15 27 13 S07E41 0340 EKI EKO beta-gamma

area: 0520

S2115 2012.12.14       N04W60         plage
S2116 2012.12.14   8 1 N08E07 0010   BXO  
11634 2012.12.15 1 4 2 S13E42 0070 HSX CAO area: 0150

location: S13E44

Total spot count: 33 46 20  
Sunspot number: 83 86 60  (total spot count + 10 * number of spotted regions)
Weighted SN: 63 66 40  (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): 50 30 33 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
2012.12 105.8 (1) 32.2 (2A) / 58.7 (2B) / 47.1 (2C) (59.3 projected, -0.7) (3.82)

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.