Solar Terrestrial Activity Report

Last major update issued on May 13, 2012 at 06:15 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 unsettled on May 12. Solar wind speed at SOHO ranged between 452 and 623 km/s. SOHO recorded what appears to be a solar wind shock at 13:13 UTC, this caused an increase in solar wind speed to above 600 km/s and a minor increase in geomagnetic activity. The event was observed in ACE at the same time as a sudden increase in the total field of the IMF. The source of the event was likely a small CME on May 9 or 10.

Solar flux measured at 20h UTC on 2.8 GHz was 129.5 (increasing 27.8 over the last solar rotation). The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.1). Three hour interval K indices: 32223233 (planetary), 32222323 (Boulder).

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

At midnight UTC the visible solar disk had 11 spotted active regions (in 2K resolution SDO images).

Region 11476 [N08W22] decayed significantly losing penumbral area and spots. While there are still magnetic delta structures within the region, they are smaller and weaker than they were a few days ago. M class flares are possible.
Region 11477 [S23E21] was quiet and stable.
Region 11478 [S24E30] was quiet and stable.
Region 11479 [N14E54] was quiet and stable. SWPC is including S1646 in this region, an interpretation which is not supportable by magnetic polarity analysis.
Region 11480 [S17W18] decayed and could soon become spotless.

Spotted active regions not numbered by NOAA/SWPC:
S1642 [S15W04] was quiet and stable.
S1646 [N15E64] was quiet and stable.
S1647 [N12E22] decayed slowly and quietly.
New region S1648 [S26E64] emerged early in the day near the southeast limb.
New region S1649 [S10E75] rotated into view at the southeast limb.
New region S1650 [N05W34] emerged to the southwest of AR 11476.

Coronal mass ejections (CMEs)

May 10: No obviously Earth directed significant CMEs were observed in STEREO imagery.
May 11: A filament eruption began after 18h UTC 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.

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 to good.

Forecast

The geomagnetic field is expected to be quiet to active on May 13 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 unsettled 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				N16W66						plage location: N17W59
11475	2012.05.02				N05W64						location: N06W52
11476	2012.05.04 2012.05.05	40	89	49	N11W18	0960	FKC	FKC			beta-gamma-delta location: N08W22
S1631	2012.05.04				S24W51						plage
S1633	2012.05.06				N12W40						plage
11477	2012.05.07 2012.05.08	1	3	1	S21E19	0040	HSX	CSO			location: S23E21 area: 0080
11478	2012.05.08 2012.05.10	1	4	2	S24E30	0060	HSX	CSO			area: 0110
11480	2012.05.08 2012.05.11		1		S16W24	0000		AXX			location: S17W18
S1637	2012.05.08				N23W55						plage
S1638	2012.05.08				S19W59						plage
S1642	2012.05.09		3		S15W04	0000		AXX
11479	2012.05.10 2012.05.11	3	2	1	N15E57	0130	DSO	HSX			location: N14E54
S1645	2012.05.10				S12W04						plage
S1646	2012.05.11		7	5	N15E64	0100		DSO			area: 0110
S1647	2012.05.11		1		N12E22	0000		AXX
S1648	2012.05.12		4	2	S26E64	0010		BXO
S1649	2012.05.12		1	1	S10E75	0050		HSX
S1650	2012.05.12		2	2	N05W34	0010		CRO
Total spot count:		45	117	63
Sunspot number:		85	227	143	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		70	155	101	(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):		51	79	79	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.