Solar Terrestrial Activity Report

Last major update issued on February 25, 2013 at 05:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update February 1, 2013)] [Cycle 24 progress (last update February 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update February 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update February 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update February 3, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated February 3, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was very quiet on February 24. Solar wind speed at SOHO ranged between 282 and 346 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 94.9 (decreasing 2.7 over the last solar rotation). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.1). Three hour interval K indices: 11010101 (planetary), 12122210 (Boulder).

The background x-ray flux was at the class B2 level.

At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).

Region 11673 [S12W48] decayed slowly and quietly.
Region 11675 [N12W79] decayed slowly and quietly.
Region 11676 [S18W23] gained some penumbral spots and lost all umbral area.
Region 11679 [S13W15] reemerged with a penumbra spot.

Spotted regions not numbered by SWPC:
S2247 [S15E25] was quiet and stable.
S2249 [S02W23] developed slowly and quietly.
New region S2251 [S28E48] emerged with several spots.
New region S2252 [N16E76] rotated into view with a single spot.
New region S2253 [N30E17] emerged with penumbra spots.
New region S2254 [N08W29] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

February 22-24: 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 (CH556) will likely rotate into an Earth facing position on February 27-28. A northern hemisphere coronal hole (CH557) could rotate into a potentially geoeffective position on March 1.

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 February 25-28.

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 2K resolution) 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 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
11673	2013.02.14 2013.02.15		8		S10W48	0013		BXO
11675	2013.02.15 2013.02.16	2	1	1	N12W76	0040	CSO	HRX			area: 0020
11676	2013.02.16	3	13	3	S13W23	0020	DSO	BXO			location: S18W23
11677	2013.02.16 2013.02.17				S28W30						plage
11679	2013.02.17		1		S10W20	0003		AXX
S2242	2013.02.17				N18W39						plage
S2247	2013.02.21		2		S18E25	0005		AXX
S2248	2013.02.22				S18E06						plage
S2249	2013.02.22		5	1	S02W23	0016		BXO
S2250	2013.02.23				N24W21						plage
S2251	2013.02.24		8	5	S28E48	0050		DRO
S2252	2013.02.24		1	1	N16E76	0040		HSX
S2253	2013.02.24		2		N30E17	0004		AXX
S2254	2013.02.24		1		N08W29	0003		AXX
Total spot count:		5	42	11
Sunspot number:		25	142	61	(total spot count + 10 * number of spotted regions)
Weighted SN:		15	53	22	(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):		15	50	34	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.