Solar Terrestrial Activity Report

Last major update issued on October 26, 2013 at 05:05 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 25. Solar wind speed at SOHO ranged between 279 and 413 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 161.4 (increasing 55.7 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 115.5. The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.4). Three hour interval K indices: 00100101 (planetary), 01001211 (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 11 active regions in 2K resolution (SN: 266) and 9 active regions in 1K resolution (SN: 161) SDO images on the visible solar disk.

Region 11872 [S17W63] decayed slowly and quietly.
Region 11873 [N12W63] was quiet and stable.
Region 11875  [N06W38] produced a few low level C flares and decayed quickly in the trailing spot section. There is still a magnetic delta structure in the trailing spot section and a major flare is possible.
Region 11877 [S12W16] was mostly unchanged and quiet. There's a weak magnetic delta structure in a penumbra to the northwest of the main penumbra. M class flares are posssible.
Region 11879 [S12W02] matured and was quiet.
Region 11881 [S22E22] gained a few spots and was quiet.
Region 11882 [S09E63] was very active during the day and has a strong magnetic delta structure in the main penumbra. Further major flares are likely as long as the delta structure persists. C5+ flares: M2.9 at 03:02, X1.7 at 08:01 (associated with a faint asymmetric halo CME), M1.0 at 10:12, C7.9 at 14:38, X2.1 at 15:03 (associated with an asymmetric full halo CME), M1.3 at 17:09, M2.3 at 19:21, M1.9/1N at 20:58 UTC.

Spotted regions not numbered by SWPC:
S2753 [N19W83] was quiet and stable.
S2774 [S16W72] was quiet and stable.
S2776 [N13E05] was quiet and stable.
New region S2781 [N26E48] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

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.
October 25: A faint asymmetric halo CME was observed after the X1.7 event at 08h while a significantly larger full halo asymmetric CME was observed after the X2.1 flare near 15h. The latter CME will likely reach Earth on October 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

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 good. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on October 26. On October 27 unsettled to major storm conditions are possible due to effects from the CMEs observed on October 24 and 25.

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	1			N18W84	0000	AXX				plage location: N20W95 SWPC had moved this region to the location of AR S2753
S2753	2013.10.13		2		N19W83	0010		AXX
11872	2013.10.14 2013.10.15	4	2	1	S18W67	0050	CSO	HRX			area: 0015 location: S17W63
11873	2013.10.14 2013.10.16		1	1	N11W61	0007		AXX
11874	2013.10.16 2013.10.17				S11W89						plage
11875	2013.10.16 2013.10.17	39	70	29	N07W36	0660	EKC	EKC			beta-gamma-delta area: 0850 location: N06W38
S2767	2013.10.17				S05W51						plage
11877	2013.10.18	16	37	17	S12W16	0390	DHI	DHC			beta-gamma-delta area: 0500
S2769	2013.10.18				N18W35						plage
11879	2013.10.21	11	14	8	S13W03	0110	CAI	DAO			area: 0160
11880	2013.10.21				N12W72						plage
S2774	2013.10.22		4	2	S16W72	0022		CRO
11881	2013.10.22 2013.10.24	2	11	4	S22E21	0010	BXO	CRO			area: 0040
S2776	2013.10.22		4		N13E05	0013		BXO
S2777	2013.10.22				N35W07						plage
11882	2013.10.23 2013.10.24	5	10	8	S08E59	0280	DKO	DKC			area: 0370 location: S09E63
S2779	2013.10.23				S20W37						plage
S2780	2013.10.24				S10E33						plage
S2781	2013.10.25		1	1	N26E48	0004		AXX
Total spot count:		78	156	71
Sunspot number:		148	266	161	(total spot count + 10 * number of spotted regions)
Weighted SN:		118	200	115	(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	93	89	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.