Solar Terrestrial Activity Report

Last major update issued on October 28, 2013 at 05:15 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 27. Solar wind speed at SOHO ranged between 270 and 313 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 166.9 (increasing 62.0 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 116.5. 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: 00101010 (planetary), 00102221 (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 10 active regions in 2K resolution (SN: 237) and 8 active regions in 1K resolution (SN: 144) SDO images on the visible solar disk.

Region 11875  [N06W66] developed with the leader spot increasing its area significantly, a magnetic delta structure developed in the northern part of the large penumbra. The region became more unstable and was the most active on the solar disk during the day. The activity continued into the early hours of October 28 with a major X1.0 flare at 02:03 (with an associated partial halo CME) and a major M5.1 flare at 04:41 UTC. Further major flares are possible. C5+ flares: M3.5/1F at 12:48, C9.1/1F at 17:53 UTC. CMEs were observed off the west limbs after these events.
Region 11877 [S12W42] was mostly quiet and stable.
Region 11879 [S12W28] regained trailing polarity umbrae and was quiet.
Region 11881 [S23W07] lost the trailing spots.
Region 11882 [S10E35] lost one of the magnetic delta structures, however, the region is developing and could produce major flares.
Region 11883 [N02E61] was quiet and stable.
Region 11884 [S15E67] shares the negative polarity area with AR 11885 and will be regarded as one region. M flares are possible.

Spotted regions not numbered by SWPC:
New region S2784 [S17E23] emerged with a few spots.
New region S2785 [N10W80] is an emerging flux region which had a penumbra spot by the end of the day.
New region S2786 [N07E05] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

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.
October 26: An asymmetric halo CME was observed after the M1.8 LDE near 11h. Due to many other CMEs it is difficult to determine if this one was full or partial halo. The CME could reach Earth on October 29.
October 27: The CMEs originating in AR 11875 does not appear to be Earth directed.
October 28: A partial halo CME was observed in LASCO imagery after the X1 flare early in the day. The CME could reach Earth on October 30 or 31.

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

Forecast

The geomagnetic field is expected to be quiet to minor storm on October 28-30 due to CME effects.

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
11873	2013.10.14 2013.10.16	1			N13W90	0010	HRX				rotated out of view
11875	2013.10.16 2013.10.17	40	25	18	N07W64	0790	FKC	EKC			beta-gamma-delta area: 1200 location: N06W66
11877	2013.10.18	20	31	10	S12W43	0330	DHI	CHI
11879	2013.10.21	8	17	6	S12W28	0100	CAO	DSO
11881	2013.10.22 2013.10.24	2	3	2	S22W05	0010	BXO	HRX
S2776	2013.10.22				N08W31						plage
S2777	2013.10.22				N35W33						plage
11882	2013.10.23 2013.10.24	31	32	16	S08E34	0390	DKC	DKC			beta-gamma-delta area: 0700
S2780	2013.10.24				S10E07						plage
S2781	2013.10.25				N26E22						plage
11883	2013.10.26	2	4	3	N04E59	0060	HAX	CAO			location: N02E61
11884	2013.10.26	11	17	7	S13E68	0110	DSO	DSI			beta-gamma area: 0450 location: S15E67
11885	2013.10.26	1			S18E63	0130	HSX				part of AR 11884
S2784	2013.10.27		6	2	S17E23	0050		DRO
S2785	2013.10.27		1		N10W80	0003		AXX
S2786	2013.10.27		1		N07E05	0004		AXX
Total spot count:		116	137	64
Sunspot number:		206	237	144	(total spot count + 10 * number of spotted regions)
Weighted SN:		169	188	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):		124	83	79	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.