Solar Terrestrial Activity Report

Last major update issued on October 25, 2013 at 04:40 UTC. Minor update posted at 16:15 UTC

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update October 1, 2013)] [Cycle 24 progress (last update October 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update October 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update October 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update October 9, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated October 10, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was very quiet on October 24. Solar wind speed at SOHO ranged between 300 and 386 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 160.6 (increasing 52.7 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 114.9. The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.9). Three hour interval K indices: 11010000 (planetary), 01011211 (Boulder).

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

At the time of counting spots (see image time) spots were observed in 12 active regions in 2K resolution (SN: 295) and 9 active regions in 1K resolution (SN: 184) SDO images on the visible solar disk.

Region 11872 [S17W49] was quiet and stable.
Region 11873 [N11W46] was quiet and stable.
Region 11875  [N06W22] lost spots and decayed slightly. There is still a significant magnetic delta structure in the trailing spot section. A major flare is possible. C5+ flares: C9.3/1F at 05:58, M2.5/1F at 10:09, M3.5 at 10:33 UTC.
Region 11877 [S12W03] was mostly unchanged and still has a number of spots around the northern half of the large penumbra. Further major flares are possible. C5+ flares: major M9.3/1N at 00:28 (associated with a faint halo CME), C5.7 at 22:10 UTC.
Region 11879 [S12E12] developed slowly and quietly.
New region 11881 [S22E37] emerged on October 22 and was numbered by SWPC 2 days later.
New region 11882 [S09E78] rotated partly into view on October 23 and has large trailing penumbra. The region produced an M2.9 flare at 03:02 UTC on October 25.

Spotted regions not numbered by SWPC:
S2753 [N18W71] developed slowly and quietly.
S2769 [N18W22] was quiet and stable.
S2774 [S17W58] was quiet and stable.
S2776 [N15E15] was quiet and stable.
New region S2780 [S10E46] emerged with a penumbra spot.

A large filament eruption was observed in the northeast quadrant early on October 25.

Minor update posted at 16:15 UTC: AR 11882 has produced 2 X class flares today. The first was an impulsive X1.7 event at 08:01 and was associated with a relatively small CME off the east limb. Then at 15:03 an impulsive X2.1 flare peaked. The region has a magnetic delta structure in the trailing penumbra and is likely to produce further major flares as long as that structure persists.

Coronal mass ejections (CMEs)

October 22: A partial CME was observed early in the day following a filament eruption in the northeast quadrant. A small halo CME was associated with the M4 event in AR 11875 late in the day.
October 23: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
October 24: A faint halo CME was observed after the M9 event in AR 11877 early in the day.

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

No obvious coronal holes are currently in or near Earth facing positions.

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 active on October 25 due to CME effects. On October 26 unsettled to minor storm conditions are possible due to effects from the CME observed early on Oct.24.

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 2K resolution) 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 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
11869	2013.10.12 2013.10.13				N16W70						plage location: N20W82
S2753	2013.10.13		3	1	N18W72	0015		BXO
11871	2013.10.14				N16W76						plage
11872	2013.10.14 2013.10.15	2	3	1	S18W54	0070	DSO	CSO
11873	2013.10.14 2013.10.16		3		N11W47	0010		BXO
11874	2013.10.16 2013.10.17				S11W75						plage
11875	2013.10.16 2013.10.17	50	66	38	N08W23	0720	EKC	FKC			beta-gamma-delta area: 1000 location: N06W22
S2767	2013.10.17				S05W38						plage
11877	2013.10.18	19	48	26	S12W03	0440	DKC	DKC			beta-gamma-delta area: 0500
S2769	2013.10.18		3		N18W22	0007		BXO
11879	2013.10.21	11	28	13	S12E10	0100	CAI	DAI			area: 0190
11880	2013.10.21				N12W58						plage
S2774	2013.10.22		4	3	S17W58	0023		CRO
11881	2013.10.22 2013.10.24	4	7	5	S22E37	0010	BXO	BXO			area: 0027
S2776	2013.10.22		5	3	N15E15	0014		AXX
S2777	2013.10.22				N35E06						plage
11882	2013.10.23 2013.10.24	2	4	4	S08E73	0100	DSO	DKO			area: 0360 location: S09E78
S2779	2013.10.23				S20W24						plage
S2780	2013.10.24		1		S10E46	0002		AXX
Total spot count:		88	175	94
Sunspot number:		148	295	184	(total spot count + 10 * number of spotted regions)
Weighted SN:		123	218	137	(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):		89	103	101	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 the 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.