Solar Terrestrial Activity Report

Last major update issued on September 4, 2012 at 05:30 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 September 3, 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 active to major storm on September 3. Solar wind speed at SOHO ranged between 287 and 453 km/s. A solar wind shock was observed at ACE at 11:23 UTC, the arrival of the August 31 CME.

Solar flux measured at 20h UTC on 2.8 GHz was 141.6 (increasing 13.5 over the last solar rotation). The Potsdam WDC planetary A index was 38 (STAR Ap - based on the mean of three hour interval ap indices: 38.3). Three hour interval K indices: 44446554 (planetary), 33645435 (Boulder).

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

At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).

Region 11553 [S21W81] was mostly quiet as it rotated to the southwest limb.
Region 11558 [N15W14] developed slowly and quietly.
Region 11560 [N03W32] still has a magnetic delta structure centrally, however, the region only managed to produce a few small C flares. A minor M class flare is possible. The region is decaying slowly and lost a large part of its umbral area during the day.
Region 11561 [S10W38] gained a few spots, however, the two northernmost spots could be a separate group.
Region 11562 [S18W03] was quiet and stable.
Region 11563 [S26E15] decayed slowly and quietly.
Region 11564 [S14E28] developed further and has significant polarity intermixing. An M class flare is possible. The region was the most active one on the visible disk producing a number of small C flares.
New region 11565 [N11E22] emerged on September 2 and was numbered by SWPC the next day. The region developed on September 3.
New region 11566 [N22E79] rotated into view.

Spotted regions not numbered by NOAA/SWPC:
S1897 [S22W08] developed slowly and quietly.
New region S1898 [N09E26] was split off from AR 11565.
New region S1899 [N10W30] emerged with a tiny spot.

Coronal mass ejections (CMEs)

September 1, 3: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
September 2: A full faint halo CME was observed early in the day and could reach Earth on September 5.

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 northern hemisphere coronal hole (CH532) was in an Earth facing position on September 2-3, CH532 appears to have closed during the latter half of 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. Propagation on long distance northeast-southwest paths is good.

Forecast

The geomagnetic field is expected to be quiet to minor storm on September 4-6 due to CME effects and quiet to unsettled on September 7.

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	3	3	2	S21W82	0090	DSO	DSO
11555	2012.08.24 2012.08.25				N08W54						plage
11557	2012.08.27				N17W60						plage
11558	2012.08.27	3	13	8	N13W23	0010	AXX	CRO			location: N15W14
S1881	2012.08.27				S19W56						plage
S1882	2012.08.27				N23W33						plage
11559	2012.08.27 2012.08.28				N17W18						originally AR 11558
S1884	2012.08.27				N15W35						plage
11560	2012.08.29	23	43	25	N03W33	0350	EKI	EAC			beta-gamma-delta
11561	2012.08.29 2012.08.30	3	7	4	S10W40	0010	HRX	CRO
11562	2012.08.29 2012.08.30	3	10	2	S19W07	0010	BXI	CRO			location: S18W03
S1890	2012.08.29				S18W18						plage
11563	2012.08.30	5	12	7	S26E15	0070	DRO	BXO
11564	2012.08.30 2012.08.31	19	64	28	S16E26	0220	ESI	EAC
S1894	2012.09.01				S02W10						plage
S1895	2012.09.02				S08E14						plage
11565	2012.09.02 2012.09.03	6	9	5	N11E21	0040	DAO	DAO			area: 0100
S1897	2012.09.02		9	4	S22W08	0030		CRO
11566	2012.09.03	1	1	1	N24E76	0060	HAX	HSX			location: N22E79
S1898	2012.09.03		2	2	N09E26	0000		BXO
S1899	2012.09.03		1		N10W30	0000		AXX
Total spot count:		66	174	88
Sunspot number:		156	294	198	(total spot count + 10 * number of spotted regions)
Weighted SN:		102	211	125	(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):		94	103	109	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.