Solar Terrestrial Activity Report

Last major update issued on October 17, 2012 at 06:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update October 3, 2012)] [Cycle 24 progress (last update October 1, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update October 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update October 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update October 1, 2012)]

[POES auroral activity level since October 2009 - updated October 7, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on October 16. Solar wind speed at SOHO ranged between 336 and 499 km/s. A high speed stream from CH541 arrived near 23h UTC at SOHO with wind speed increasing to near 500 km/s. A mino

Solar flux measured at 20h UTC on 2.8 GHz was 137.0 (increasing 27.2 over the last solar rotation). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.0). Three hour interval K indices: 22221212 (planetary), 12312211 (Boulder).

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

At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).

Region 11586 [S13W55] was quiet and stable.
Region 11589 [N12W17] decayed further losing spots and penumbral area. No mature penumbra was observed.
Region 11590 [S30W05] decayed slowly and quietly.
Region 11591 [N06E19] was mostly quiet and stable.
Region 11592  [N23W03] decayed slowly and quietly.
Region 11593 [N16E63] was quiet and stable.
Region 11594 [S27E48] was quiet. In the presence of minor polarity intermixing there is a chance of C class flaring.

Spotted regions not numbered by NOAA/SWPC:
S1977 [S14W27] developed slowly and quietly.
S1988 [S12E06] lost the spot from the previous day and gained another further north.
New region S1990 [N20E11] emerged with tiny spots.

Coronal mass ejections (CMEs)

October 14-16: 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  northern hemisphere coronal hole (CH541) was Earth facing on October 13. Another northern hemisphere coronal hole (CH542) could rotated into an Earth facing position on October 17-18.

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 poor to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on October 17-18 due to effects from CH541, isolated active intervals are possible. Quiet conditions are likely on October 19-20 becoming quiet to unsettled on October 21 due to effects from CH542

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
11586	2012.10.06 2012.10.07	1	1	1	S12W54	0040	HSX	HSX
11589	2012.10.09	13	38	16	N12W19	0080	DRI	DRI
11590	2012.10.10 2012.10.11	7	5	4	S30W07	0020	CRO	CRO
11591	2012.10.11 2012.10.12	6	17	7	N07E20	0190	DSO	CHO			beta-gamma area: 0280
S1977	2012.10.11		2	2	S14W27	0010		CRO
11592	2012.10.12 2012.10.14	1	5	1	N22W08	0010	AXX	BXO
S1979	2012.10.12				S24W57						plage
S1980	2012.10.12				N13W58						plage
11594	2012.10.14 2012.10.15	6	15	6	S26E47	0090	DAO	CAO			location: S28E63
S1984	2012.10.14				N03W13						plage
S1985	2012.10.14				N05W37						plage
11593	2012.10.15	3	3	2	N15E62	0060	HAX	HAX
S1986	2012.10.15				N22E24						plage
S1987	2012.10.15				N08E59						plage
S1988	2012.10.15		1		S12E06	0000		AXX
S1989	2012.10.15				S25W18						plage
S1990	2012.10.16		2		N20E11	0000		AXX
Total spot count:		37	89	39
Sunspot number:		107	189	119	(total spot count + 10 * number of spotted regions)
Weighted SN:		58	123	73	(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):		64	66	65	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) Boulder SN current 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.