Solar Terrestrial Activity Report

Last major update issued on May 18, 2012 at 04:05 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 on May 17. Solar wind speed at SOHO ranged between 344 and 461 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 136.3 (decreasing 5.4 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.9). Three hour interval K indices: 21111111 (planetary), 21112212 (Boulder).

The background x-ray flux is at the class B7 level.

At midnight UTC the visible solar disk had 15 spotted active regions (in 2K resolution SDO images).

Region 11476 [N10W90] produced a long duration major M5.1 proton event peaking at 01:47 UTC before rotating out of view. This event was associated with a fast and wide partial halo CME. The region has become more unstable after the LDE and further M class events are possible while the region is less than 2 days behind the northwest limb.
Region 11477 [S23W45] decayed slowly and quietly.
Region 11478 [S24W35] was quiet and stable.
Region 11479 [N12W12] was quiet and stable.
Region 11481 [S10E12] decayed slowly and quietly.
Region 11482 [N13W04] developed slowly and could produce C and minor M class flares.
Region 11483 [S26W04 decayed slowly and quietly.
Region 11484 [N09E25] developed slowly and could produce C and minor M class flares.
Region 11485 [S19E40] decayed slowly and quietly.

Spotted active regions not numbered by NOAA/SWPC:
S1647 [N12W35] reemerged with a single spot.
S1654 [S25E28] decayed slowly and quietly.
S1655 [S17W02] was quiet and stable.
S1659 [N09E55] was quiet and stable.
New region S1662 [N16E80] rotated into view at the northeast limb.
New region S1663 [N12E34] emerged with two tiny spots.
New region S1664 [N22W07] emerged with two spots.

Coronal mass ejections (CMEs)

May 15-16: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.
May 17: A partial halo CME was observed after an M5 LDE in AR 11476 early in the day.

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 (CH517) will likely rotate into an Earth facing position on May 18-19.

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 to unsettled most of May 18. Late in the day or sometime on May 19 the CME observed on May 17 could reach Earth and cause some unsetttled and active intervals. Quiet to unsettled is likely on May 20. A high speed stream from CH517 could arrive on May 21 and cause quiet to active conditions until May 23.

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
11476	2012.05.04 2012.05.05	2			N12W86	0150	CAO				rotated out of view
11477	2012.05.07 2012.05.08	1	3	1	S20W45	0020	HRX	HRX			location: S23W45
11478	2012.05.08 2012.05.10	1	1	1	S22W36	0060	HSX	HSX			area: 0110 location: S24W35
11479	2012.05.10 2012.05.11	1	9	4	N14W12	0050	HSX	CSO			area: 0110 location: N12W12
11482	2012.05.11 2012.05.13	10	37	20	N14W03	0190	DAI	DHI			beta-gamma area: 0400
S1647	2012.05.11		1	1	N12W35	0000		AXX
11483	2012.05.12 2012.05.13		2		S26W01	0000		AXX			location: S26W04
11481	2012.05.12 2012.05.13	1	2	2	S10E06	0010	AXX	AXX			location: S10E12
11484	2012.05.13	15	36	19	N09E24	0230	DAI	DAI			area: 0350
S1651	2012.05.13				N31W12						plage
S1652	2012.05.13				S03W57						plage
S1653	2012.05.13				N28W49						plage
S1654	2012.05.14		1	1	S25E28	0000		AXX
S1655	2012.05.14		6	2	S17W02	0000		BXO
S1656	2012.05.14				S32W56						plage
S1659	2012.05.15		5		N09E55	0000		AXX
S1660	2012.05.15				S05W48						plage
S1661	2012.05.15				N33E16						plage
11485	2012.05.15	3	4	2	S19E37	0010	BXO	BXO			location: S19E40
S1662	2012.05.17		2	2	N16E80	0280		HHX
S1663	2012.05.17		2	1	N12E34	0000		BXO
S1664	2012.05.17		2	1	N22W07	0000		AXX
Total spot count:		34	113	57
Sunspot number:		114	263	187	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		62	151	95	(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):		68	92	103	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.