Solar Terrestrial Activity Report

Last major update issued on February 27, 2013 at 04:40 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 quiet on February 26. Solar wind speed at SOHO ranged between 286 and 347 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 98.7 (increasing 2.1 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 12111121 (planetary), 02221221 (Boulder).

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

At midnight UTC the visible solar disk had 5 spotted active regions (in 2K resolution SDO images).

Region 11680 [S29E24] decayed slowly and quietly.
Region 11681 [N17E47] gained a few spots and was quiet.
Region 11682 [S18W03] developed further. The region has a magnetically simple structure.

Spotted regions not numbered by SWPC:
New region S2259 [S13E38] emerged with penumbra spots.
New region S2260 [N15W18] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

February 23-25: 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 rotate into an Earth facing position on February 26-28. 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on February 27-28. Quiet to active conditions are possible on March 1-5 due to effects from CH556 and CH557.

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				S10W76						plage
11676	2013.02.16				S18W53						plage
11677	2013.02.16 2013.02.17				S28W58						plage
11679	2013.02.17				S10W48						plage
11682	2013.02.21 2013.02.25	11	19	14	S18W03	0170	DAC	DAC			area: 0320
S2248	2013.02.22				S18W20						plage
S2249	2013.02.22				S02W49						plage
S2250	2013.02.23				N24W47						plage
11680	2013.02.24 2013.02.25	5	12	7	S28E23	0040	DAO	CRI
11681	2013.02.24 2013.02.25	3	11	3	N16E46	0040	CSO	CSO
S2253	2013.02.24				N37E09						plage
S2254	2013.02.24				N08W55						plage
S2255	2013.02.25				S28E15						plage
S2256	2013.02.25				N12W73						plage
S2257	2013.02.25				N03W25						plage
S2258	2013.02.25				S08W09						plage
S2259	2013.02.26		2	2	S13E38	0009		BXO
S2260	2013.02.26		1		N15W18	0003		AXX
Total spot count:		19	45	26
Sunspot number:		49	95	66	(total spot count + 10 * number of spotted regions)
Weighted SN:		34	58	39	(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):		29	33	36	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.