Solar Terrestrial Activity Report

Last major update issued on October 1, 2012 at 05:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update September 8, 2012)] [Cycle 24 progress (last update October 1, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 8, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 8, 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 September 8, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to minor storm on September 30. Solar wind speed at SOHO ranged between 279 and 392 km/s. A minor disturbance began near noon, likely due to the arrival of a minor CME  (unknown source). The CME observed on September 28 arrived at 22:21 UTC at SOHO and has caused a strong geomagnetic disturbance. Early on October 1 severe storming has been observed.

Solar flux measured at 20h UTC on 2.8 GHz was 135.6 (decreasing 6.0 over the last solar rotation). The Potsdam WDC planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.0). Three hour interval K indices: 22233325 (planetary), 11123323 (Boulder).

The background x-ray flux is at the class B8 level.

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

Region 11575 [N07W87] decayed slowly and quietly as it rotated to the northwest limb. Events attributed by SWPC to this region occurred in AR 11583.
Region 11577 [N08W71] produced a few minor C flares as it approached the northwest limb.
Region 11579 [S10W07] was quiet and stable.
Region 11580 [N17E04] was quiet and stable.
Region 11582 [S13E17] was quiet and stable.
Region 11583 [N13W87] rotated partly out of view and was the most active region during the day. The largest flares were an M1.3 event at 04:33 and a C9.9 event at 23:39 UTC.
New region 11584 [S24E29] emerged quickly and could produce more C flares.

Spotted regions not numbered by NOAA/SWPC:
S1929 [N07W54] reemerged with several spots.
S1943 [N17W11] was quiet and stable.
S1944 [N17W79] developed slowly and quietly as it rotated to the northwest limb.
S1952 [N09W62] was quiet and stable.
New region S1953 [N12W14] emerged with two spots.

Coronal mass ejections (CMEs)

September 29-30: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
September 28: A CME was observed in STEREO imagery early in the day following the long duration C3.7 event late on Sept.27.

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 poorly defined coronal hole (CH537) in the northern hemisphere will rotate into an Earth facing position on October 1-2. A recurrent coronal hole (CH538) in the southern hemisphere will rotate into an Earth facing position on October 5-6.

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

Forecast

The geomagnetic field is expected to be unsettled to severe storm on October 1 due to CME effects. Quiet to unsettled is likely on October 2-3.

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
11575	2012.09.17 2012.09.18	1	1	1	N07W87	0100	HSX	HRX
11576	2012.09.18 2012.09.19				S21W75						plage location: S23W69
11581	2012.09.19 2012.09.25				N22W66						plage
S1929	2012.09.21		7	2	N07W54	0010		BXO
11577	2012.09.22	8	5	2	N09W68	0090	DAO	CAO
11579	2012.09.23 2012.09.24	4	14	4	S09W08	0180	CSO	CHO			area: 0310
S1936	2012.09.23				N06W39						plage
11578	2012.09.24	2			N21W75	0010	CAO				plage
S1937	2012.09.24				S22W10						plage
11580	2012.09.24 2012.09.25		4		N19E14	0000		BXO
S1940	2012.09.24				N28W57						plage
11582	2012.09.25 2012.09.26	1	5	1	S12E15	0350	HHX	CHO			area: 0450
S1943	2012.09.26		4	1	N17W11	0000		AXX
S1944	2012.09.26		3	1	N17W79	0030		CRO
S1946	2012.09.27				S12W41						plage
11583	2012.09.27 2012.09.29	6	2	1	N12W88	0090	DSO	CRO
S1949	2012.09.27				S25W48						plage
S1950	2012.09.28				N18W35						plage
S1951	2012.09.29				S19W16						plage
S1952	2012.09.29		5	2	N09W62	0010		BXO
11584	2012.09.30	3	12	7	S23E28	0010	CAO	DRI			area: 0070
S1953	2012.09.30		2	2	N12W14	0010		BXO
Total spot count:		25	64	24
Sunspot number:		95	184	134	(total spot count + 10 * number of spotted regions)
Weighted SN:		65	101	61	(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	64	74	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. 2C) STAR SDO 1K Wolf number 30 day average.
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.