Solar Terrestrial Activity Report

Last major update issued on August 10, 2013 at 05:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update August 1, 2013)] [Cycle 24 progress (last update August 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 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 July 28, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on August 9. Solar wind speed at SOHO ranged between 344 and 478 km/s. A high speed stream from CH578 began to influence the field after 08h UTC. The interplanetary magnetic field was mostly northwards which resulted in only a weak disturbance.

Solar flux measured at 20h UTC on 2.8 GHz was 103.6 (decreasing 10.4 over the last solar rotation). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 12222121 (planetary), 13332322 (Boulder).

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

At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11809 [N11W54] was quiet and stable.
Region 11810 [S25W43] decayed slowly and quietly.
Region 11813 [S13W33] decayed slowly and quietly.
Region 11814 [S26E36] was quiet and stable.
Region 11816 [S19E34] was quiet and stable.

Spotted regions not numbered by SWPC:
S2594 [S22E49] developed slowly and quietly.
New region S2595 [S20E62] emerged with penumbra spots.
New region S2596 [S07E74] rotated into view with a couple of spots and produced the only C flare of the day.

Coronal mass ejections (CMEs)

August 7-9: 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 recurrent coronal hole (CH579) in the northern hemisphere will likely rotate into an Earth facing position on August 11-14.

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 on August 10-13. A high speed stream from CH579 could cause quiet to minor storm conditions on August 14-17.

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
11809	2013.07.30	1	6	2	N11W53	0030	HAX	CSO
11810	2013.07.31		4		S24W48	0009		BXO			location: S25W43
S2580	2013.07.31				S15W58						plage
S2581	2013.07.31				S11W50						plage
S2585	2013.08.03				N13W30						plage
S2586	2013.08.03				N17W15						plage
S2587	2013.08.03				N24W29						plage
11813	2013.08.04 2013.08.07	8	19	6	S13W33	0070	CAO	CAI
11814	2013.08.06 2013.08.07	1	2	2	S26E36	0020	HAX	HSX			area: 0060
11816	2013.08.06 2013.08.07	1	3	2	S21E33	0010	HRX	HRX			area: 0018
S2593	2013.08.06				S12W46						plage
11815	2013.08.07				N08W72						plage
S2594	2013.08.08		5	2	S22E49	0017		BXO
S2595	2013.08.09		2		S20E62	0007		BXO
S2596	2013.08.09		2	2	S07E74	0030		HRX
Total spot count:		11	43	16
Sunspot number:		51	123	76	(total spot count + 10 * number of spotted regions)
Weighted SN:		29	64	37	(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):		31	43	42	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.