Solar Terrestrial Activity Report

Last major update issued on July 28, 2013 at 06:50 UTC.

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

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated June 30, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to unsettled on July 27. Solar wind speed at SOHO ranged between 385 and 480 km/s under the slowly weakening influence of a high speed stream from CH576.

Solar flux measured at 20h UTC on 2.8 GHz was 107.9 (increasing 5.1 over the last solar rotation). The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.4). Three hour interval K indices: 32223223 (planetary), 44232322 (Boulder).

The background x-ray flux was at the class B4 level.

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

Region 11800 [S07W56] decayed slowly. There is still polarity intermixing and at least C class events are possible.
Region 11801 [N20E18] was quiet and stable.
Region 11803 [S10W42] was quiet and stable.
Region 11805 [S06W29] developed significantly and could produce C flares.
New region 11806 [S15E58] rotated into view on July 26 and was numbered by SWPC the next day.

Spotted regions not numbered by SWPC:
S2566 [S14W28] was quiet and stable.
S2570 [S13E22] was quiet and stable.
New region S2573 [S17E08] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

July 24-26: 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 trans equatorial coronal hole (CH576) was in an Earth facing position on July 22-23.

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 fair.

Forecast

The geomagnetic field is expected to be mostly quiet on July 28-30.

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
11798	2013.07.17 2013.07.18				S12W84						plage
11799	2013.07.17 2013.07.18				S16W60						plage
11800	2013.07.17 2013.07.18	17	23	10	S08W60	0210	DAO	DAC			beta-gamma location: S07W56 area: 0320
11803	2013.07.18 2013.07.23		3		S09W45	0004		BXO
11801	2013.07.22 2013.07.23	1	8	1	N20E16	0090	HSX	CSO			area: 0110
S2566	2013.07.23		2	2	S14W28	0006		AXX
S2567	2013.07.23				N22W20						plage
11805	2013.07.24 2013.07.25	4	25	10	S06W30	0030	CSO	DAI			area: 0140
S2570	2013.07.25		2	1	S13E22	0005		AXX
11806	2013.07.26 2013.07.27	2	6	3	S16E57	0010	AXX	CRO			area: 0030
S2573	2013.07.27		1	1	S17E08	0004		AXX
Total spot count:		24	70	28
Sunspot number:		64	150	98	(total spot count + 10 * number of spotted regions)
Weighted SN:		39	88	46	(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):		38	53	54	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.