Solar Terrestrial Activity Report

Last major update issued on July 27, 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 active on July 26. Solar wind speed at SOHO ranged between 437 and 558 km/s under the influence of a high speed stream from CH576.

Solar flux measured at 20h UTC on 2.8 GHz was 109.5 (increasing 9.3 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: 10.8). Three hour interval K indices: 43222222 (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 11793 [N21W81] decayed slowly and quietly.
Region 11800 [S07W44] developed and became more compact. C and M class flaring is possible.
Region 11801 [N20E33] was quiet and stable.
Region 11803 [S08W29] was quiet and stable.
Region 11805 [S06W15] was quiet and stable.

Spotted regions not numbered by SWPC:
S2566 [S16W18] was quiet and stable.
S2570 [S13E34] was quiet and stable.
New region S2572 [S14E71] rotated into view.

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 quiet to unsettled on July 27, decreasingly under the influence of the high speed stream from CH576. Quiet conditions are likely 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
11793	2013.07.13 2013.07.14	2	2	1	N21W81	0070	CSO	CSO
11798	2013.07.17 2013.07.18				S12W70						plage
11799	2013.07.17 2013.07.18				S16W46						plage
11800	2013.07.17 2013.07.18	12	26	14	S08W46	0160	DAI	DAC			beta-gamma location: S07W44 area: 0400
11803	2013.07.18 2013.07.23		7		S09W31	0011		BXO
S2560	2013.07.19				N18W54						plage
11801	2013.07.22 2013.07.23	1	4	1	N20E30	0080	HSX	CSO			area: 0110
11802	2013.07.22 2013.07.23				N14W89						rotated out of view
S2565	2013.07.23				S12E38						plage
S2566	2013.07.23		1		S17W18	0002		AXX
S2567	2013.07.23				N22W17						plage
11805	2013.07.24 2013.07.25	3	9	4	S07W16	0020	CSO	DRO			location: S07W18 area: 0040
S2570	2013.07.25		3		S13E34	0008		AXX
S2571	2013.07.25				N42W45						plage
S2572	2013.07.26		2	1	S14E71	0015		HRX
Total spot count:		18	54	21
Sunspot number:		58	134	71	(total spot count + 10 * number of spotted regions)
Weighted SN:		38	75	42	(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):		35	47	39	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.