Solar Terrestrial Activity Report

Last major update issued on March 31, 2012 at 04:30 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 28, 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 to unsettled on March 30. Solar wind speed at SOHO ranged between 313 and 392 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 110.6 (decreasing 0.9 over the last solar rotation). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.9). Three hour interval K indices: 32211101 (planetary), 22212211 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).

Region 11438 [S14W61] decayed further and could become spotless today.
Region 11443 [N13W43] was quiet and stable.
Region 11445 [S22W17] decayed slowly and quietly.
Region 11448 [S17E30] decayed slowly and quietly.
Region 11449 [S18W32] was quiet and decayed in the trailing spot section.

Spotted regions not reported by NOAA/SWPC:
[S1548] emerged in the northeast quadrant on March 23 and developed quickly on March 26. Slow decay was observed on March 27 while new spots emerged in the leading spot section on March 28 resulting in minor polarity intermixing. The region decayed on March 29-30. SWPC has this as AR 11442, a region which was originally further west. Location at midnight: N12W54.
[S1552] reemerged with spots on March 29. Location at midnight: N12W37
[S1553] rotated into view at the southeast limb on March 27. Location at midnight: S17E41
[S1558] emerged in the southeast quadrant on March 28. Location at midnight: S30W01
[S1559] emerged in an old plage area in the northeast quadrant on March 29. On March 30 the single spot disappeared while another further west became visible. Location at midnight: N22W32
[S1560] emerged in the northeast quadrant on March 30. Location at midnight: N16E52
[S1561] rotated into view at the northeast limb early on March 30. This is likely old AR 11429, now a region with few and small spots.

Coronal mass ejections (CMEs)

March 28-30: 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 small coronal hole (CH510) in the northern hemisphere was in an Earth facing position on March 30.

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 poor.

Forecast

The geomagnetic field is expected to be quiet on March 31 and April 1. Weak effects from CH510 are possible on April 2.

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
11438	2012.03.19 2012.03.20	2	2		S13W65	0020	CSO	BXO			location: S14W61
11442	2012.03.21 2012.03.22	5			N12W54	0070	DAO				spotless location: N12W58 SWPC data is for AR S1548
11443	2012.03.21 2012.03.22	2	9	4	N13W44	0010	BXO	BXO
11444	2012.03.22 2012.03.23				N21W58						plage location: N19W50
11445	2012.03.23	4	7	1	S22W13	0180	CSO	CHO			area: 0250 location: S22W17
S1547	2012.03.23				N29W36						plage
S1548	2012.03.23		7	6	N12W54	0040		CRO
11448	2012.03.26 2012.03.28	3	5	4	S17E29	0030	CAO	BXO
S1552	2012.03.26		1	1	N12W37	0000		AXX
S1553	2012.03.27		2	1	S17E41	0000		AXX
S1554	2012.03.27				N16W29						plage
S1555	2012.03.27				S21W51						plage
11449	2012.03.28 2012.03.29	3	7	3	S18W31	0040	CAO	CRO
S1558	2012.03.28		4		S30W01	0000		BXO
S1559	2012.03.29		1		N22W32	0000		AXX
S1560	2012.03.30		6	2	N16E52	0010		CRO
S1561	2012.03.30		3	1	N18E70	0000		BXO
Total spot count:		19	54	23
Sunspot number:		79	174	113	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		44	73	42	(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):		47	61	62	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.