Solar Terrestrial Activity Report

Last major update issued on May 17, 2012 at 04:45 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 16. Solar wind speed at SOHO ranged between 344 and 447 km/s. A minor magnetic cloud arrived near noon in the trailing part of the CME which reached Earth on May 15. This caused an increase in disturbance levels during the latter half of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 130.9 (decreasing 6.9 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: 22212234 (planetary), 21112224 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight UTC the visible solar disk had 13 spotted active regions (in 2K resolution SDO images).

Region 11476 [N10W76] decayed further as it approached the west limb. Early on May 17 the region produced a major M5.1 long duration proton event peaking at 01:47 UTC. It is too early to tell if the associated CME has any Earth directed components.
Region 11477 [S23W31] decayed slowly and quietly.
Region 11478 [S25W22] was quiet and stable.
Region 11479 [N13E01] was quiet and stable.
Region 11481 [S11E23] was quiet and stable.
Region 11482 [N13E09] developed further and could produce C flares.
Region 11483 [S27E13] decayed quickly and quietly.
Region 11484 [N09E38] developed slowly and could produce further C class flares.
Region 11485 [S19E53] displayed no major changes and was quiet.

Spotted active regions not numbered by NOAA/SWPC:
S1654 [S27E44] decayed slowly and quietly.
S1655 [S17E12] was quiet and stable.
S1659 [N10E68] was quiet and stable.
S1660 [S05W35] developed slowly and quietly.

Coronal mass ejections (CMEs)

May 14-16: 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

No significant coronal holes are currently in or near Earth facing positions.

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 to very poor. Propagation on long distance northeast-southwest paths is fair.

Forecast

The geomagnetic field is expected to be mostly quiet on May 17-19.

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	3	4	3	N13W73	0230	CAO	CHO			location: N10W76 area: 0350
11477	2012.05.07 2012.05.08	1	9	3	S21W32	0010	AXX	HRX			location: S23W31
11478	2012.05.08 2012.05.10	1	1	1	S22W23	0060	HSX	HSX			area: 0120 location: S25W22
S1642	2012.05.09				S18W52						plage
11479	2012.05.10 2012.05.11	3	5	4	N10E01	0050	CSO	CSO			area: 0100 location: N13E01
S1645	2012.05.10				S12W56						plage
11482	2012.05.11 2012.05.13	9	29	13	N13E10	0130	CAO	DKI			area: 0350
S1647	2012.05.11				N13W24						plage
11483	2012.05.12 2012.05.13	1	5		S26E13	0010	AXX	BXO
11481	2012.05.12 2012.05.13	1	3	2	S10E19	0010	AXX	CRO			location: S11E23
11484	2012.05.13	9	30	16	N09E38	0120	DAO	DAI			area: 0300
S1651	2012.05.13				N31E01						plage
S1652	2012.05.13				S03W44						plage
S1653	2012.05.13				N28W36						plage
S1654	2012.05.14		4		S27E44	0000		BXO
S1655	2012.05.14		6	3	S17E12	0000		BXO			count includes 1 spot outside of image
S1656	2012.05.14				S32W43						plage
S1657	2012.05.14				S22W58						plage
S1659	2012.05.15		1	1	N10E68	0000		AXX
S1660	2012.05.15		2	2	S05W35	0010		BXO
S1661	2012.05.15				N33E29						plage
11485	2012.05.15	4	10	5	S20E51	0010	BXO	CRO			location: S19E53 area: 0020
Total spot count:		32	109	53
Sunspot number:		122	239	163	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		70	153	97	(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):		73	84	90	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.