Solar Terrestrial Activity Report

Last major update issued on May 14, 2012 at 04:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 3, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 3, 2012)]

[POES auroral activity level since October 2009 - updated May 12, 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 active on May 13. Solar wind speed at SOHO ranged between 443 and 540 km/s, likely under the influence of a high speed stream from CH516 most of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 130.5 (increasing 22.6 over the last solar rotation). The Potsdam WDC planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 13.5). Three hour interval K indices: 34322233 (planetary), 33322233 (Boulder).

The background x-ray flux is at the class B4 level.

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

Region 11476 [N09W34] decayed further with the largest penumbra becoming symmetric. An M class flare is still a possibility. Flares: C4.4 at 04:08, C7.0/1F at 08:14 UTC
Region 11477 [S23E08] was quiet and stable.
Region 11478 [S24E17] was quiet and stable.
Region 11479 [N13E41] was quiet and stable.
New region 11481 [S10E61] rotated into view at the southeast limb on May 12 and got an SWPC number the next day.
New region 11482 [N14E49] rotated into view at the southeast limb on May 11 and was recognized as an active region by SWPC two days later.
New region 11483 [S26E52] emerged near the southeast limb early on May 12 and was assigned a number by SWPC the next day.
New region 11484 [N12E79] rotated into view at the northeast limb.

Spotted active regions not numbered by NOAA/SWPC:
S1647 [N13E16] lost the leader spot and gained a spot in the trailing polarity area.
New region S1651 [N31E40] emerged with a single, tiny spot.
New region S1652 [S03W05] emerged near center disk with a tiny spot.
New region S1653 [N28E03] emerged with a tiny spot.

Coronal mass ejections (CMEs)

May 11-12: A filament eruption began after 18h UTC on May 11 and involved a large area around the center of the disk, including the southern part of AR 11476, AR 11480 and extending towards the east. A CME was observed in STEREO-B at 23:54 UTC and in STEREO-A a couple of hours later when images resumed. LASCO displays a slow and small halo CME. The CME is likely Earth directed.
May 13: No obviously Earth directed CMEs were observed in LASCO or 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 southern hemisphere coronal hole (CH516) was Earth facing on May 9-10.

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 unsettled on May 14 due to a high speed stream from CH516. Quiet to unsettled is likely on May 14. The CME observed late on May 11 / early on May 12 could reach Earth on May 15 and cause quiet to active conditions.

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
11474	2012.05.01 2012.05.02				N16W80						plage location: N17W72
11475	2012.05.02				N05W79						location: N06W65
11476	2012.05.04 2012.05.05	44	72	36	N09W33	0810	FKI	FHI			beta-gamma-delta
S1633	2012.05.06				N12W53						plage
11477	2012.05.07 2012.05.08	1	4	2	S23E07	0050	HSX	CSO
11478	2012.05.08 2012.05.10	1	2	1	S24E16	0060	HSX	HSX			area: 0120
11480	2012.05.08 2012.05.11				S16W38						plage location: S17W31
S1642	2012.05.09				S15W17						plage
11479	2012.05.10 2012.05.11	1	3	2	N15E40	0040	HSX	HSX			location: N13E41 area: 0070
S1645	2012.05.10				S12W17						plage
11482	2012.05.11 2012.05.13	2	18	10	N14E51	0080	DSO	DSI
S1647	2012.05.11		1	1	N13E15	0000		AXX
11483	2012.05.12 2012.05.13	7	9	5	S27E51	0010	BXO	CRO
11481	2012.05.12 2012.05.13	1	1	1	S10E61	0040	HSX	HSX
S1650	2012.05.12				N05W47						plage
11484	2012.05.13	1	3	2	N10E75	0020	HSX	DSO			area: 0080 location: N10E79
S1651	2012.05.13		1		N31E40	0000		AXX
S1652	2012.05.13		1	1	S03W05	0000		AXX
S1653	2012.05.13		1		N28E03	0000		AXX
Total spot count:		58	116	61
Sunspot number:		138	236	161	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		98	159	104	(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):		83	83	89	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 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.