Solar Terrestrial Activity Report

Last major update issued on September 17, 2013 at 03:15 UTC.

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

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated September 5, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on September 16. Solar wind speed at SOHO ranged between 321 and 372 km/s. A low speed stream associated with CH586 became the dominant solar wind source after 22h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 94.5 (decreasing 37.0 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 115.5. The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 21211112 (planetary), 11221112 (Boulder).

The background x-ray flux was at the class B2 level.

At the time of counting spots (see image time) there were 10 active regions in 2K resolution (SN: 121) and 5 active regions in 1K resolution (SN: 59) SDO images with spots on the visible solar disk.

Region 11840 [S12W73] was quiet and stable.
Region 11841 [S04E04] decayed slowly and quietly.

Spotted regions not numbered by SWPC:
S2682 [S08W23] was quiet and stable.
New region S2685 [S09E63] emerged with a penumbra spot.
New region S2686 [S18E77] rotated into view.
New region S2687 [N10E82] rotated into view with penumbra spots.
New region S2688 [N01E21] emerged with penumbra spots.
New region S2689 [N23W43] emerged with several spots.
New region S2690 [S12W13] emerged with penumbra spots.
New region S2691 [S30W30] emerged with a penumbra spot in an old plage area.

Coronal mass ejections (CMEs)

September 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 trans equatorial coronal hole (CH586) was in an Earth facing position on September 13-14. A coronal hole (CH587) in the northern hemisphere will likely rotate into an Earth facing position on September 19-20.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled with a chance of active intervals on September 17 due to effects from CH586. Quiet conditions are likely on September 18-21 becoming quiet to unsettled on September 22-23 as a stream from CH587 influences the geomagnetic field.

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
11838	2013.09.04 2013.09.05				S05W84						plage
11840	2013.09.05 2013.09.11	2	2	1	S11W75	0010	BXO	BXO
S2667	2013.09.10				S18W29						plage
11841	2013.09.10 2013.09.11	1	3	2	S04E02	0030	HSX	CAO			location: S04E04
S2669	2013.09.10				N13W23						plage
S2674	2013.09.11				N15W33						plage
S2675	2013.09.11				N20W29						plage
S2677	2013.09.12				S28W44						plage
S2678	2013.09.13				S12W27						plage
S2679	2013.09.13				N15W38						plage
S2681	2013.09.13				S14W41						plage
S2682	2013.09.13		1		S08W23	0003		AXX
S2684	2013.09.15				S31E25						plage
S2685	2013.09.16		1		S09E83	0002		AXX
S2686	2013.09.16		1	1	S18E77	0005		AXX
S2687	2013.09.16		2		N10E82	0006		AXX
S2688	2013.09.16		2		N01E21	0004		BXO
S2689	2013.09.16		5	3	N23W43	0028		CRO
S2690	2013.09.16		3	2	S12W13	0011		BXO
S2691	2013.09.16		1		S30W30	0002		AXX
Total spot count:		3	21	9
Sunspot number:		23	121	59	(total spot count + 10 * number of spotted regions)
Weighted SN:		8	29	17	(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):		14	42	32	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.