Solar Terrestrial Activity Report

Last major update issued on May 7, 2012 at 04:35 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 5, 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 6. Solar wind speed at SOHO ranged between 285 and 331 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 117.6 (increasing 23.1 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.9). Three hour interval K indices: 11222110 (planetary), 21222211 (Boulder).

The background x-ray flux is at the class B8 level.

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11470 [S17W40] decayed slowly and quietly.
Region 11471 [S22W36] decayed slowly and quietly.
Region 11474 [N15E17] added several small trailing spots.
Region 11475 [N06E26] added a few spots and was quiet.
Region 11476 [N11E61] is a complex region with major polarity intermixing and several magnetic delta structures. The two most significant deltas are in a central northern penumbra and in the trailing penumbra. A major flare is possible. Flares: impulsive M1.1 at 01:18, M1.3/1N at 17:47 UTC as well as many sub C5 level flares.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
S1633 [N12E08] emerged with a single tiny spot.

Coronal mass ejections (CMEs)

May 4-6: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. There's a slight chance one or two of the small CMEs observed on May 4 and 5 could have Earth directed components.

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 (CH515) will rotate into an Earth facing position on May 5-7. Another recurrent trans equatorial coronal hole (CH516) will likely become 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 fair to good. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on May 7. From late on May 8 until May 10 a high speed stream from CH515 will likely cause quiet to minor storm conditions with a chance of major storm intervals.

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
11469	2012.04.23 2012.04.24	2			S26W90	0040	CSO				rotated out of view
11471	2012.04.27 2012.04.28	8	16	7	S19W36	0210	DAO	CSI			location: S22W36
11470	2012.04.27 2012.04.28	5	8	5	S15W43	0030	CRO	CRO			location: S17W40
S1618	2012.04.28				N21W38						plage
11472	2012.04.29				S28W52						plage location: S30W45
S1621	2012.04.30				N18W53						plage
11474	2012.05.01 2012.05.02	3	8	4	N13E17	0010	HRX	CRO			location: N15E17
11475	2012.05.02	1	4	3	N05E25	0005	AXX	CRO
S1626	2012.05.02				S28W28						plage
11476	2012.05.04 2012.05.05	25	41	28	N10E63	0760	FHI	FKC			beta-gamma-delta area: 1100 location: N11E61
S1629	2012.05.04				S16E00						plage
S1630	2012.05.04				N27W17						plage
S1631	2012.05.04				S24E27						plage
S1633	2012.05.06		1	1	N12E38	0000		AXX
Total spot count:		44	78	48
Sunspot number:		104	138	108	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		70	102	72	(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):		62	48	59	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.