Solar Terrestrial Activity Report

Last major update issued on May 6, 2012 at 06:00 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 5. Solar wind speed at SOHO ranged between 275 and 329 km/s..

Solar flux measured at 20h UTC on 2.8 GHz was 116.0 (increasing 22.7 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: 3.8). Three hour interval K indices: 11112101 (planetary), 11022212 (Boulder).

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

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11470 [S17W27] was mostly quiet and stable.
Region 11471 [S22W22] developed polarity intermixing with new small spots emerging to the north and southeast of the leading penumbra.
Region 11472 [S30W32] was quiet and stable.
Region 11474 [N14E28] was quiet and stable.
Region 11475 [N05E37] was quiet and stable.
New region 11476 [N11E75] rotated partly into view at the northeast limb on May 4 and was numbered the next day by SWPC. As the trailing penumbra is now in view it is obvious that this is a large and complex region capable of producing a major flare. A central penumbra has a magnetic delta structure and frequent flaring is likely to continue as long as that structure persists. Flares: C6.8 at 09:35, impulsive M1.4 at 13:23, impulsive M1.3 at 23:01 UTC. Many flares below the C5 level were recorded as well.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
S1611 [S27W79] decayed slowly and quietly.

An active region just behind the southeast limb could rotate into view later today.

Coronal mass ejections (CMEs)

May 3-5: 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.

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 6-7. On May 8-10 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			S25W77	0060	CSO				location: S21W77 spotless SWPC has S1611 and 11469 as one region
11467	2012.04.24				N13W77						plage location: N15W70
S1611	2012.04.25		2	1	S27W79	0060		HAX
11471	2012.04.27 2012.04.28	8	22	12	S19W24	0150	DAO	DKO			location: S22W22
11470	2012.04.27 2012.04.28	2	18	7	S15W31	0010	BXO	CRI			location: S17W27 area:0030
S1618	2012.04.28				N21W25						plage
11472	2012.04.29		1		S28W38	0000		AXX			location: S30W32
S1619	2012.04.29				S13W59						plage
S1621	2012.04.30				N18W40						plage
11473	2012.05.01	1			S20W89	0010	AXX				rotated out of view
11474	2012.05.01 2012.05.02	1	3	2	N13E30	0010	AXX	HRX			location: N14E28
11475	2012.05.02	1	1	1	N04E39	0010	AXX	HRX			location: N05E37
S1626	2012.05.02				S28W15						plage
S1627	2012.05.03				N05W48						plage
11476	2012.05.04 2012.05.05	3	23	9	N09E67	0360	DKO	FKC			beta-gamma-delta area: 0900 location: N11E75
S1629	2012.05.04				S16E13						plage
S1630	2012.05.04				N27W04						plage
S1631	2012.05.04				S24E40						plage
S1632	2012.05.04				S13W76						plage
Total spot count:		18	70	32
Sunspot number:		88	140	92	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		38	104	62	(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):		53	49	51	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.