Solar Terrestrial Activity Report

Last major update issued on September 2, 2012 at 06:45 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 September 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 to unsettled on September 1. Solar wind speed at SOHO ranged between 275 and 329 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 145.6 (increasing 11.6 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.8). Three hour interval K indices: 22321112 (planetary), 12332322 (Boulder).

The background x-ray flux is at the class C1 level.

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

Region 11553 [S21W54] decayed slightly but may still have minor M class flaring potential.
Region 11555 [N08W25] was quiet and stable.
Region 11558 [N16E06] was quiet and stable.
Region 11560 [N03W05] developed further with a magnetic delta structure forming in the trailing spot section. A major flare is possible. The region was the source of a long duration C2.8 event peaking before 04h UTC on September 2. This event was associated with a CME which could be aimed at Earth given the center disk location of the source. STEREO-A displays a CME, however, LASCO imagery may change the evaluation of the importance of the CME.
Region 11561 [S12W11] was quiet and stable.
Region 11562 [S17E26] was quiet and stable.
Region 11563 [S26E43] developed slowly and quietly.
Region 11564 [S15E57] developed slowly and has minor M class flare potential.

Spotted regions not numbered by NOAA/SWPC:
S1890 [S19E07] added a few tiny spots.
S1893 [S12W68] decayed slowly and quietly.
New region S1894 [S02E16] emerged with two spots.

Coronal mass ejections (CMEs)

August 30 and September 1: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
August 31: A large and bright full halo CME was observed following a filament eruption in the southeast quadrant. This CME could reach Earth during the latter half of September 3.

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 could rotate into an Earth facing position on September 3.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on September 2. A CME could reach Earth on September 3 and cause active to major storm conditions that day and on September 4. The CME observed early on September 2 could reach Earth on September 5 and cause unsettled to minor storm conditions.

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
11553	2012.08.22 2012.08.23	8	8	6	S22W57	0150	DAI	DSI			area: 0270 location: S21W54
11554	2012.08.23 2012.08.24	4			N15W94	0160	DAO				rotated out of view
11555	2012.08.24 2012.08.25		16	4	N08W26	0010		BXO
S1876	2012.08.25				N16W59						plage
11557	2012.08.27				N17W32						plage
11558	2012.08.27		7	4	N13E10	0010		BXO			location: N16E06
S1881	2012.08.27				S19W30						plage
S1882	2012.08.27				N23W07						plage
11559	2012.08.27 2012.08.28				N17E10						originally AR 11558
S1884	2012.08.27				N13W08						plage
S1885	2012.08.28				N24W41						plage
S1886	2012.08.28				N08W37						plage
11560	2012.08.29	19	36	21	N03W05	0220	DAI	EAC			beta-gamma-delta area: 0650
11561	2012.08.29 2012.08.30	2	5	3	S12W10	0030	DAO	DRO
11562	2012.08.29 2012.08.30	4	12	7	S16E25	0020	DAO	DRO
S1890	2012.08.29		4	1	S19E07	0000		AXX
11563	2012.08.30	4	9	6	S25E43	0070	DSO	DAO
11564	2012.08.30 2012.08.31	9	22	11	S14E56	0090	DAO	DAI
S1892	2012.08.30				N12W56						plage
S1893	2012.08.31		1		S16W68	0000		AXX
S1894	2012.09.01		2	2	S02E16	0005		BXO
Total spot count:		50	122	65
Sunspot number:		120	232	165	(total spot count + 10 * number of spotted regions)
Weighted SN:		85	148	91	(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):		72	81	91	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.