Solar Terrestrial Activity Report

Last major update issued on August 31, 2012 at 06:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update August 6, 2012)] [Cycle 24 progress (last update August 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 6, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 6, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 5, 2012)]

[POES auroral activity level since October 2009 - updated August 5, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was very quiet on August 30. Solar wind speed at SOHO ranged between 350 and 457 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 127.8 (decreasing 11.9 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: 3.5). Three hour interval K indices: 11111011 (planetary), 11122211 (Boulder).

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

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

Region 11553 [S21W30] developed further with the major spots in a compact configuration. A minor M class flare is possible.
Region 11554 [N16W66] was quite active during the first half of the day, however, as the magnetic layout simplified activity ceased and the region is decaying. Flare: C7.6 at 09:12 UTC
Region 11555 [N07E03] decayed slowly and quietly.
Region 11558 [N17E36] decayed and could soon become spotless. This is AR 11559 in SWPC data but was originally AR 11558.
Region 11560 [N03E24] developed further and is quickly becoming the most interesting region on the visible disk. A magnetic delta structure has formed in a trailing penumbra. M flares are possible.
New region 11561 [S12E16] emerged on August 29 and was numbered the next day by SWPC.
New region 11562 [S17E52] emerged on August 29 and got its NOAA number the next day.
New region 11563 [S26E70] rotated into view. The region produced an M1.3 flare at 12:11 UTC.

Spotted regions not numbered by NOAA/SWPC:
S1884 [N13E18] was quiet and stable.
S1885 [N24W15] reemerged with a tiny spot.
S1890 [S23E36] decayed and could soon become spotless.
New region S1891 [S15E83] rotated partly into view.
New region S1892 [N13W29] emerged with a few spots.

Coronal mass ejections (CMEs)

August 28-30: 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 small trans equatorial coronal hole (CH531)  was in an Earth facing position on August 27.

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 quiet to unsettled on August 31 due to weak effects from CH531 and quiet on September 1-2.

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. 0.5k 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
11552	2012.08.20 2012.08.21				S17W63						plage
11553	2012.08.22 2012.08.23	7	14	7	S21W30	0150	DSO	DSC			area: 0400 location: S21W17 count includes 1 tiny leader spot not in image
11554	2012.08.23 2012.08.24	5	9	5	N16W65	0090	DAO	DAO			area: 0200
11555	2012.08.24 2012.08.25	11	22	8	N08E01	0030	CSO	CRO
S1876	2012.08.25				N16W33						plage
S1877	2012.08.25				N12W49						plage
S1880	2012.08.26				N28W45						plage
11557	2012.08.27				N17W03						plage
11558	2012.08.27		3		N13E37	0000		BXO
S1881	2012.08.27				S19W04						plage
S1882	2012.08.27				N23E19						plage
11559	2012.08.27 2012.08.28	2			N17E37	0010		AXX			originally AR 11558
S1884	2012.08.27		2		N13E18	0000		AXX
S1885	2012.08.28		1		N24W15	0000		AXX
S1886	2012.08.28				N08W24						plage
11560	2012.08.29	8	21	14	N03E22	0050	DAO	DSI			beta-gamma-delta area: 0450
11561	2012.08.29 2012.08.30	3	11	7	S12E15	0020	CAO	DRI			area: 0060
11562	2012.08.29 2012.08.30	1	3	2	S16E56	0010	AXX	DRO
S1889	2012.08.29				N17W53						plage
S1890	2012.08.29		1		S23E36	0000		AXX
11563	2012.08.30	1	8	4	S25E71	0010	AXX	DAO			area: 0130
S1891	2012.08.30		4	2	S15E83	0020		CRO			area: 0130
S1892	2012.08.30		2	1	N13W29	0010		CRO			area: 0130
Total spot count:		38	101	50
Sunspot number:		118	231	140	(total spot count + 10 * number of spotted regions)
Weighted SN:		63	136	85	(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):		71	81	77	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 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.