Solar Terrestrial Activity Report

Last major update issued on September 1, 2013 at 04:50 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 August 4, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated August 20, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to active on August 31. Solar wind speed at SOHO ranged between 363 and 427 km/s under the influence of a low speed stream from CH582.

Solar flux measured at 20h UTC on 2.8 GHz was 107.5 (increasing 2.7 over the last solar rotation). The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.0). Three hour interval K indices: 43322102 (planetary), 44322312 (Boulder).

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

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11834 [N13W22] decayed slowly and quietly.
Region 11835 [S10W12] was mostly quiet and stable.
Region 11836 [N11E19] gained a few spots and produced the only C flare of the day.

Spotted regions not numbered by SWPC:
S2647 [S13E17] gained spots and was quiet.
New region S2649 [S04E30] emerged with a penumbra spot.
New region S2650 [S16E12] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

August 29, 31: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
August 30: An asymmetric full halo CME was observed after the LDE in AR 11836 early in the day. The CME will likely reach Earth during the latter half of September 1 or early on September 2.

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 recurrent trans equatorial coronal hole (CH583) will rotate into an Earth facing position on August 31 and September 1.

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 initially on September 1. Sometime during the latter half of the day or early on September 2 the CME observed on August 30 will likely reach Earth and cause unsettled to minor storm conditions. Quiet to unsettled conditions are likely on September 3.

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
S2629	2013.08.23				N07W53						plage
11834	2013.08.23 2013.08.24	12	24	9	N13W20	0030	CRI	DRI
11835	2013.08.24	9	20	11	S11W13	0140	DSC	DSI			area: 0270
S2633	2013.08.24				S10W21						plage
11836	2013.08.26 2013.08.27	9	20	12	N11E19	0180	EAO	EAO
S2638	2013.08.26				S20W42						plage
S2639	2013.08.26				S11W26						plage
S2643	2013.08.27				N03W27						plage
S2645	2013.08.29				N33E22						plage
S2646	2013.08.30				S14E54						plage
S2647	2013.08.30		6	3	S13E17	0014		CRO
S2648	2013.08.30				N42E47						plage
S2649	2013.08.31		1		S04E30	0002		AXX
S2650	2013.08.31		1		S16E12	0001		AXX
Total spot count:		30	72	35
Sunspot number:		60	132	75	(total spot count + 10 * number of spotted regions)
Weighted SN:		43	88	51	(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):		36	46	41	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.