Solar Terrestrial Activity Report

Last major update issued on May 5, 2012 at 06:25 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 4. Solar wind speed at SOHO ranged between 289 and 332 km/s..

Solar flux measured at 20h UTC on 2.8 GHz was 114.0 (increasing 18.3 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: 4.0). Three hour interval K indices: 22011211 (planetary), 22001211 (Boulder).

The background x-ray flux is at the class B9 level.

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

Region 11469 [S21W64] decayed slowly and could become spotless today.
Region 11470 [S16W16] decayed slowly and quietly.
Region 11471 [S22W07] was mostly quiet with the large penumbra elongating longitudinally.
Region 11472 [S29W18] decayed further losing all leading polarity spots, the region could become spotless today.
Region 11473 [S20W78] was quiet and stable.
Region 11474 [N14E42] was quiet and stable.
Region 11475 [N05E51] decayed slowly and quietly.

Spotted active regions not numbered by NOAA/SWPC:
S1611 [S26W63] decayed slowly and quietly. Apparently SWPC considers the region to be part of AR 11469.
S1621 [N18W27] was quiet and stable.
S1626 [S28W02] reemerged with tiny spots.
New region S1628 [N10E83] rotated partly into view at the northeast limb revealing a large leading penumbra. A major flare is possible from this region.
New region S1629 [S16E26] emerged in CH515 with tiny spots.
New region S1630 [N27E09] emerged in the northeast quadrant.
New region S1631 [S24E53] emerged with a tiny spot.
New region S1632 [S13W63] emerged with several spots.

Coronal mass ejections (CMEs)

May 2-4: No obviously Earth directed CMEs were observed in LASCO and 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

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. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on May 5-7. 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	5	3		S25W62	0080	DAO	BXO			location: S21W64 area: 0000 SWPC has S1611 and 11469 as one region
11467	2012.04.24				N13W63						plage location: N15W57
S1611	2012.04.25		9	4	S26W63	0080		DAO
11471	2012.04.27 2012.04.28	7	15	7	S19W10	0300	HHX	CKO			location: S22W07
11470	2012.04.27 2012.04.28	7	14	9	S15W20	0020	CRO	DRO			location: S16W16 area:0040
S1618	2012.04.28				N21W12						plage
11472	2012.04.29	2	2		S28W24	0010	BXO	AXX
S1619	2012.04.29				S13W46						plage
S1621	2012.04.30		2		N18W27	0000		BXO
11473	2012.05.01	7	4	3	S20W79	0060	DAO	DSO
11474	2012.05.01 2012.05.02	1	2	1	N14E40	0020	HRX	HRX			location: N14E42
11475	2012.05.02	2	1	1	N06E49	0020	CAO	HRX			location: N05E51
S1626	2012.05.02		2	1	S28W02	0000		BXO
S1627	2012.05.03				N05W35						plage
S1628	2012.05.04		2	2	N10E83	0500		HKX
S1629	2012.05.04		2		S16E26	0000		BXO
S1630	2012.05.04		1	1	N27E09	0000		AXX
S1631	2012.05.04		1		S24E53	0000		AXX
S1632	2012.05.04		9	4	S13W63	0020		CRO
Total spot count:		31	69	33
Sunspot number:		101	219	133	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		62	111	75	(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):		61	77	73	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.