Solar Terrestrial Activity Report

Last major update issued on August 30, 2012 at 05:05 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 quiet on August 29. Solar wind speed at SOHO ranged between 430 and 546 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 118.3 (decreasing 16.3 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: 3.6). Three hour interval K indices: 11211001 (planetary), 12112211 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 11 spotted active regions (in 2K resolution SDO images).

Region 11553 [S21W17] developed as new flux emerged to the south and southwest of the main penumbra. At least C flares are possible.
Region 11554 [N16W52] developed quickly with new flux emerging in the central section. A new penumbra formed and expanded rapidly. This penumbra has a magnetic delta structure and there is a chance of an M class flare.
Region 11555 [N08E14] decayed slowly and quietly.
Region 11558 [N15E47] and AR 11559 is obviously one region.
New region 11560 [N03E37] emerged quickly and has a simple magnetic layout.

Spotted regions not numbered by NOAA/SWPC:
S1882 [N23E32] reemerged with a few tiny spots.
S1884 [N12E30] was quiet and stable.
New region S1887 [S12E30] emerged with two spots, the single umbra has rudimentary penumbra.
New region S1888 [S17E65] emerged with a few spots.
New region S1889 [N17W40] emerged with two tiny spots.
New region S1890 [S19E46] emerged with tiny spots.

An active region at the southeast limb produced the most energetic flare of the day, a C4.0 event at 19:58 UTC. This and another region about to rotate into view at the southeast limb could have minor M class flare potential

Coronal mass ejections (CMEs)

August 27-29: 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. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 30-31 due to weak effects from CH531 and quiet on September 1.

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
11548	2012.08.17 2012.08.18				N18W78						plage
11552	2012.08.20 2012.08.21				S17W49						plage
11553	2012.08.22 2012.08.23	5	20	6	S21W20	0130	CSO	DSO			area: 0270 location: S21W17 count includes 6 tiny leader spots not in image
11554	2012.08.23 2012.08.24	6	15	8	N17W54	0050	DSO	DAC			beta-delta area: 0200 location: N16W52
11555	2012.08.24 2012.08.25	15	21	10	N08E15	0100	DSI	CAI
S1875	2012.08.24				N10W58						plage
S1876	2012.08.25				N16W20						plage
S1877	2012.08.25				N12W36						plage
S1878	2012.08.26				N05W48						plage
S1880	2012.08.26				N28W32						plage
11557	2012.08.27				N17E10						plage
11558	2012.08.27	1	6	2	N13E51	0010	AXX	BXO			includes AR 11559, this is one region
S1881	2012.08.27				S19E09						plage
S1882	2012.08.27		2	1	N23E32	0000		AXX
11559	2012.08.27 2012.08.28	2			N17E49	0030		HRX			see AR 11558
S1884	2012.08.27		5	1	N12E30	0000		AXX
S1885	2012.08.28				N25W04						plage
S1886	2012.08.28				N08W11						plage
11560	2012.08.29	6	13	9	N04E36	0040	DAO	DRI			area: 0060
S1887	2012.08.29		2	1	S12E30	0010		CRO
S1888	2012.08.29		3	1	S17E65	0010		CRO
S1889	2012.08.29		2		N17W40	0000		BXO
S1890	2012.08.29		2		S19E46	0000		AXX
Total spot count:		35	91	39
Sunspot number:		95	201	129	(total spot count + 10 * number of spotted regions)
Weighted SN:		58	118	66	(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):		57	70	71	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.