Solar Terrestrial Activity Report

Last major update issued on July 23, 2013 at 04:20 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 22. Solar wind speed at SOHO ranged between 352 and 397 km/s, reentering the stream from CH575 during the latter half of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 109.9 (increasing 0.7 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.0). Three hour interval K indices: 00001213 (planetary), 21112313 (Boulder).

The background x-ray flux was at the class B3 level.

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

Region 11793 [N20W28] decayed quickly and quietly.
Region 11799 [S16E09] was quiet and stable.
Region 11800 [S08E09] decayed slowly and quietly.

Spotted regions not numbered by SWPC:
S2557 [S09E24] was quiet and stable.
New region S2563 [N20E84] rotated into view with a single spot.
New region S2564 [N13W36] emerged with penumbra spots.

Coronal mass ejections (CMEs)

July 20-22: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. A large backsided full halo CME from a northern hemisphere source was observed during the morning of July 22.

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 on July 23-24 with a chance of a few unsettled intervals. A high speed stream from CH576 could cause quiet to active conditions on July 25-26.

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
11791	2013.07.10 2013.07.12				S13W88						plage
11792	2013.07.10 2013.07.12				N02W88						plage
11797	2013.07.13 2013.07.17				S19W54						plage
11795	2013.07.13 2013.07.14				S06W55						plage
11793	2013.07.13 2013.07.14	14	17	7	N21W27	0170	FSO	ESO			area: 0230
S2550	2013.07.15				S21W45						plage
S2553	2013.07.16				N13W50						plage
11798	2013.07.17 2013.07.18				S12W14						plage
11799	2013.07.17 2013.07.18	1	1	1	S15E08	0010	AXX	AXX
11800	2013.07.17 2013.07.18	8	15	6	S08E08	0060	DAO	DAO
S2557	2013.07.18		8	1	S09E24	0016		BXO
S2559	2013.07.19				S13W36						plage
S2560	2013.07.19				N18W02						plage
S2562	2013.07.20				S32W43						plage
S2563	2013.07.22		1	1	N20E84	0080		HAX
S2564	2013.07.22		3		N13W30	0006		BXO
Total spot count:		23	45	16
Sunspot number:		53	105	66	(total spot count + 10 * number of spotted regions)
Weighted SN:		33	60	31	(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):		32	37	36	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.