Solar Terrestrial Activity Report

Last major update issued on February 27, 2012 at 05:30 UTC.

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

[POES auroral activity level since October 2009 - updated February 24, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on February 26. Solar wind speed ranged between 369 and 518 km/s. A solar wind shock was observed at SOHO at 21:07 UTC, the arrival of the CME observed on February 24. Active conditions have been observed early on February 27.

Solar flux measured at 20h UTC on 2.8 GHz was 107.0 (decreasing 7.4 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.0). Three hour interval K indices: 22221012 (planetary), 23331212 (Boulder).

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

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11423 [N17E31] was quiet and stable.
Region 11424 [N07E42] decayed slowly and quietly.
New region 11425 [N18E14] emerged in the northeast quadrant on February 23, was spotless on Feb.24, then reemerged on Feb.25. On Feb.26 SWPC assigned a number to the region as it developed slowly.
New region 11426 [N10E14] emerged in the northeast quadrant.

Spotted regions not reported by NOAA/SWPC:
[S1489] emerged in the southeast quadrant on February 22. Location at midnight: S15W13
[S1490] reemerged on February 25. Location at midnight: S20W02
[S1494] emerged in the northeast quadrant on February 24. Location at midnight: N15E45

Spotless region 11421 produced 2 C flares: C1.3 at 11:25 and C2.3 at 21:41 UTC

Coronal mass ejections (CMEs)

February 25-26: 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 recurrent coronal hole (CH503) in the northern hemisphere will be in an Earth facing position on February 26-27. A short lived coronal hole (CH504) formed in the northern hemisphere between AR 11421 and the filament which erupted on Feb.23-24. CH504 rotated across the central meridian and had almost closed by the end of Feb.24. A coronal hole (CH505) in the southern hemisphere will likely rotate into an Earth facing position on Feb.29-March 1.

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

Forecast

The geomagnetic field is expected to be quiet to active on February 27 due to CME effects and a high speed stream from CH504. Mostly quiet conditions are likely on Feb.28-29. A high speed stream from CH503 could cause quiet to unsettled conditions on March 1.

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
			2K	1K
11421	2012.02.17 2012.02.18				N14W48						plage
11422	2012.02.18 2012.02.19	3			N15W90	0150	CAO				rotated out of view
S1489	2012.02.22		1		S15W13	0000		AXX
S1490	2012.02.22		1	1	S20W02	0000		AXX
11423	2012.02.22 2012.02.23	1	3	2	N17E29	0090	HSX	CSO			location: N17E31 area: 0200
11425	2012.02.23 2012.02.26	1	4	2	N18E12	0010	HRX	CRO
11424	2012.02.24	1	4	2	N07E39	0020	HRX	CRO			location: N07E42
S1494	2012.02.24		3	2	N15E45	0010		AXX
S1495	2012.02.25				S20E14						plage
11426	2012.02.26	2	6	3	N10E12	0020	DRO	BXO
Total spot count:		8	22	12
Sunspot number:		58	92	72	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		27	33	23	(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):		35	41		k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1, 2011) for STAR SDO 2K

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.