Solar Terrestrial Activity Report

Last major update issued on December 25, 2011 at 05:10 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 24. Solar wind speed ranged between 339 and 384 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 142.8 (increasing 7.6 over the last solar rotation). The planetary A index was 1 (STAR Ap - based on the mean of three hour interval ap indices: 0.9). Three hour interval K indices: 00000001 (planetary), 00111221 (Boulder).

The background x-ray flux is at the class B6 level.

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

Region 11380 [S22W14] developed as new flux emerged in the trailing polarity area. The region currently has reversed polarities.
Region 11382 [S17W53] decayed quickly losing spots and all penumbra on the trailing spots.
Region 11383 [N04E01] was quiet and stable.
Region 11384 [N13E12] was mostly quiet with slow decay occurring in the trailing spot section.
Region 11385 [S31W13] gained a few spots and was quiet.
Region 11386 [S15E58] was quiet and added a few spots. Note that SWPC includes region S1392 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: S18E65. Flares: C5.2 at 08:39, C1.1 at 11:16 UTC
[S1393] emerged in the northeast quadrant on December 24. Location at midnight: N20E68
[S1394] emerged in the northeast quadrant on December 24. Location at midnight: N19E14

A filament eruption in the central northern hemisphere began at 23:29 UTC in SDO/AIA 193 images. A partial halo CME was observed in LASCO images, however, it is uncertain if any components are Earth directed (pending further analysis).

Coronal mass ejections (CMEs)

December 21-23: 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

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

Forecast

The geomagnetic field is expected to be quiet on December 25-27. There's a slight chance of weak CME effects on December 28. A high speed stream from CH490 could cause some unsettled and active intervals on December 29-30.

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		S19W54	0150	HSX				spotless location: S18W56
11380	2011.12.16 2011.12.17		5	S21W25	0030		DRO			location: S22W14 reversed polarities
11382	2011.12.17 2011.12.18	8	7	S18W48	0030	CSO	CSO			area: 0180 location: S17W53
11383	2011.12.18 2011.12.19	3	4	N03W00	0020	CSO	HRX			location: N04E01 area: 0010
S1380	2011.12.18			N27W39						plage
11384	2011.12.19 2011.12.20	13	20	N13E12	0480	EHO	EHO			area: 0650
S1385	2011.12.20			S03W30						plage
S1386	2011.12.20			N20W06						plage
S1387	2011.12.20			N12W29						plage
S1388	2011.12.21			S15W13						plage
11385	2011.12.21 2011.12.23	2	7	S32W16	0010	BXO	BXO
11386	2011.12.22 2011.12.23	2	4	S18E64	0120	DSO	CSO			area: 0050 location: S15E58 SWPC includes region S1392
S1392	2011.12.23		2	S18E65	0060		HSX
S1393	2011.12.24		2	N20E68	0000		BXO
S1394	2011.12.24		1	N19E14	0000		AXX
Total spot count:		30	52
Sunspot number:		90	142	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		60	83	(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):		54	64	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

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.