Solar Terrestrial Activity Report

Last major update issued on December 23, 2012 at 05:15 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 22, 2012]

Recent activity

The geomagnetic field was inactive on December 22. Solar wind speed at SOHO ranged between 334 and 447 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 115.3 (decreasing 6.3 over the last solar rotation). The Potsdam WDC planetary A index was 1 (STAR Ap - based on the mean of three hour interval ap indices: 0.8). Three hour interval K indices: 00000000 (planetary), 00111101 (Boulder).

The background x-ray flux was at the class B3 level.

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11633 [S07W23] added spots and has become more complex magnetically. A weak magnetic delta structure could be forming in a small penumbra in the northern part of the leading spot section, there's polarity intermixing in other parts of the region. C and minor M class flares are possible.
Region 11634 [S13W23] decayed slowly and quietly.
Region 11635 [N12E23] developed significantly and could produce M class flares. The region is compact and has significant polarity intermixing. A weak magnetic delta structure has formed in the northeastern section.

Spotted regions not numbered by NOAA/SWPC:
New region S2121 [S13E03] emerged with small spots.
New region S2122 [S12W12] emerged in what used to be the trailing part of AR 11634.
New region S2123 [S28E06] emerged with a tiny spot.

Coronal mass ejections (CMEs)

December 20-22: 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 recurrent trans equatorial coronal hole (CH548) will be in an Earth facing position on December 23-24. CH548 did not cause any significant disturbance during the previous rotation.

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

Forecast

The geomagnetic field is expected to be quiet on December 23-25. On December 26-27 quiet to active conditions are possible due to effects from CH548. 

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
11633	2012.12.14 2012.12.15	12	37	20	S05W27	0170	ESI	ESI			beta-gamma location: S07W26
S2116	2012.12.14				N10W53						plage
11634	2012.12.15	7	14	3	S12W25	0060	CSO	CRO			location: S13W23
11635	2012.12.18	18	39	21	N10E22	0200	ESI	DAC			beta-gamma-delta area: 0450 location: N12E23
S2117	2012.12.18				S13E16						plage
S2118	2012.12.19				N13W50						plage
S2119	2012.12.20				N07E34						plage
S2120	2012.12.20				S31W48						plage
S2121	2012.12.22		2	2	S13E03	0010		BXO
S2122	2012.12.22		6	3	S12W12	0020		CRO
S2123	2012.12.22		1		S28E06	0000		AXX
Total spot count:		37	99	49
Sunspot number:		67	159	99	(total spot count + 10 * number of spotted regions)
Weighted SN:		52	115	65	(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	56	54	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

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.