Solar Terrestrial Activity Report

Last major update issued on January 27, 2012 at 05:10 UTC. Minor update posted at 21:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update January 2, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update Jauary 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update January 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update January 5, 2012)]

[POES auroral activity level since October 2009 - updated January 25, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2117 [November-December 2011] - 2118 [December 2011 - January 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettld on January 26. Solar wind speed ranged between 388 and 521 km/s. A weak disturbance arrived at SOHO just before noon. A sudden increase in solar wind speed and temperature was recorded. The source of the disturbance was more likely a CME (transient) than a high speed coronal hole stream. ACE data does not display the transition to the disturbance as clearly as SOHO.

Solar flux measured at 20h UTC on 2.8 GHz was 128.2 (decreasing 12.9 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.8). Three hour interval K indices: 20122311 (planetary), 21222322 (Boulder).

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

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

Region 11402 [N29W74] was fairly active during the day producing several C flares. Flares: C1.5 at 00:05, C5.8 at 00:36, C7.9 at 01:49, C6.4 long duration event peaking at 05:42 (and associated with a partial halo CME), C2.8 at 20:44 UTC.
Region 11408 [N08E04] added a few small spots and was quiet.
New region 11410 [N18E76] rotated into view at the northeast limb.

Spotted regions not reported (or interpreted differently) by NOAA/SWPC:
[S1441] reemerged with a single tiny spot on January 25. Location at midnight: S13E37
[S1444] emerged in the northern hemisphere near the central meridian on January 22 and decayed on Jan.24-25. Location at midnight: N14W47
[S1446] rotated into view at the southeast limb on January 24. Location at midnight: S18E50
[S1447] emerged in the northwest quadrant on January 25. Location at midnight: N11W35
[S1448] emerged in the southeast quadrant on January 25. Location at midnight: S17E07

Minor update added at 21:20 UTC on January 27: Region 11402 produced a major X1.7 proton flare at 18:37 UTC. A significant radiation event is in progress with the above 10 MeV proton flux increasing rapidly. A large and wide partial halo CME was observed centered off the northwest limb. Due to the location of the event it is not likely that the CME will cause any significant terrestrial effects.

Coronal mass ejections (CMEs)

January 24-26: 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 large recurrent coronal hole (CH496) in the southern hemisphere was in an Earth facing position on January 23-25.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled with a possibility of some active intervals on January 27-28 due to coronal hole effects. Quiet conditions are likely on January 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
11401	2012.01.14			N16W80						plage
11402	2012.01.14	9	8	N29W72	0270	DSC	CAO			location: N29W74
11405	2012.01.15 2012.01.16	1		N13W60	0010	AXX				spotless, SWPC apparently includes S1444 in this region
11409	2012.01.20 2012.01.21			N18W14						plage
11408	2012.01.20 2012.01.21	4	11	N08E03	0110	HSX	CAO			area: 0180
S1441	2012.01.22		3	S13E18	0000		AXX
S1442	2012.01.22			N12W33						plage
S1443	2012.01.22			N17W46						plage
S1444	2012.01.22		1	N14W61	0000		AXX
S1446	2012.01.24		3	S18E50	0000		AXX
S1447	2012.01.25			N11W48						plage
S1448	2012.01.25		2	S17W06	0000		BXO
11410	2012.01.26	1	1	N16E66	0120	HSX	HSX			area: 0220 location: N18E76
S1449	2012.01.26		2	S25E36	0000		AXX
S1450	2012.01.26		2	S20E04	0000		BXO
Total spot count:		15	33
Sunspot number:		55	123	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		30	48	(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):		33	55	k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1, 2011) 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.