Solar Terrestrial Activity Report

Last major update issued on March 27, 2012 at 05:55 UTC.

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

[POES auroral activity level since October 2009 - updated March 25, 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 March 26. Solar wind speed at SOHO ranged between 310 and 364 km/s. A low speed stream associated with CH509 arrived early on March 27.

Solar flux measured at 20h UTC on 2.8 GHz was 102.4 (decreasing 0.9 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 12121101 (planetary), 02111211 (Boulder).

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

At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11438 [S14W10] decayed slowly and was mostly quiet.
Region 11443 [N13E13] was quiet and added a few small spots.
Region 11444 [N21W03] decayed slowly and quietly.
Region 11445 [S23E40] matured further and was quiet.

Spotted regions not reported by NOAA/SWPC:
[S1545] reemerged on March 26 with several spots. Location at midnight: S24W42
[S1548] emerged in the northeast quadrant on March 23 and developed quickly on March 26. C and minor M class flares are possible. SWPC failed to notice that this was a new region and reassigned AR 11442. Location at midnight: N12E03. Flares: C1.4 at 06:42, C2.7 at 23:38 UTC.
[S1551] rotated into view at the southeast limb on March 26. Location at midnight: S18E81
[S1552] emerged in the northeast quadrant on March 26. Location at midnight: N12E18

Coronal mass ejections (CMEs)

March 24-26: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. Several CMEs originating in old AR 11429 behind the northeast limb were observed over the last days.

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 (CH509) was in an Earth facing position on March 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. Propagation on long distance northeast-southwest paths is fair.

Forecast

The geomagnetic field is expected to be quiet to active on March 27-28 due to a low speed stream from CH509. Quiet conditions are likely on March 29.

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
11436	2012.03.15 2012.03.16				S14W76						plage
S1533	2012.03.18				N23W55						plage
11438	2012.03.19 2012.03.20	1	1	1	S13W10	0020	HSX	HRX			location: S14W10
S1539	2012.03.20				N05W53						plage
11442	2012.03.21 2012.03.22	3			N12W01	0030	CSO				spotless location: N12W05 SWPC data is for AR S1548
11443	2012.03.21 2012.03.22		6	4	N16E11	0010		BXO			location: N13E13
11444	2012.03.22 2012.03.23	5	4	3	N21W04	0040	CSO	AXX			area: 0010
11446	2012.03.22 2012.03.25				N23W40						plage
11445	2012.03.23	7	11	7	S23E40	0210	FAO	FSO			area: 0300
S1545	2012.03.23		6	5	S24W42	0020		DRO
S1547	2012.03.23				N29E03						plage
S1548	2012.03.23		21	9	N12E03	0080		DAI
S1550	2012.03.24				S18E23						plage
S1551	2012.03.26		1	1	S18E81	0010		HRX
S1552	2012.03.26		1		N12E18	0000		AXX
Total spot count:		16	51	30
Sunspot number:		56	131	100	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		36	70	49	(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):		34	46	55	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) 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) Month average to date.
3) Running average based on the quicklook 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.