Solar Terrestrial Activity Report

Last major update issued on July 28, 2011 at 06:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update July 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update July 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update July 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update July 2, 2011)]

[POES auroral activity level charts since October 2009 - updated July 26, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2110 [May-June 2011] - 2111 [June-July 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on July 27. Solar wind speed ranged between 335 and 448 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 99.2 (increasing 10.0 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.5). Three hour interval K indices: 12001102 (planetary), 12111211 (Boulder).

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

At midnight UTC the visible solar disk had 10 spotted regions.

Region 11260 developed further and is a complex region capable of producing M class flares, maybe even a major flare. There's a stacked double delta configuration in the main penumbra. Flares: C3.0 at 02:01, C3.0 at 06:39, C3.0 at 10:02, C3.6 at 11:31, C2.0 at 12:53, C2.0 at 13:13, M1.1/1N at 16:07, C2.3 at 21:21, C2.5 at 21:54 UTC.
Region 11261 is a compact region capable of producing M class flares.
New region 11262 emerged in the northeast quadrant on July 24 and was numbered by SWPC 3 days later. The region has mixed polarities.

Spotted regions not numbered by NOAA/SWPC:
[S1127] reemerged on July 27. Location at midnight: N05W21
[S1131] reemerged on July 26. Location at midnight: S17W20
[S1138] emerged near the southeast limb on July 27. Location at midnight: S33E65
[S1141] emerged in the northeast quadrant on July 27. Location at midnight: N16E00
[S1142] emerged in the southeast quadrant on July 27. Location at midnight: S17E58
[S1143] rotated partly into view at the northeast limb on July 27. The region could produce M flares. Location at midnight: N17E83
[S1144] emerged in the southwest quadrant on July 27. Location at midnight: S18W57

A filament eruption near 06h UTC to the west and north of region 11260 was associated with a CME off of the northeast limb. A filament eruption in the northern hemisphere near the central meridian starting near 16:50 UTC was not associated with any obvious CME.

Coronal mass ejections (CMEs)

July 25-27: No obviously earth directed CMEs were observed.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A well defined recurrent coronal hole (CH468) in the northern hemisphere was in an Earth facing position on July 26-27. CH468 may be too far to the north to cause a geomagnetic disturbance. A poorly defined trans equatorial coronal hole was Earth facing on July 26-27.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using the new method, the extent and intensity of both holes are consistent with other data sources.

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.

Forecast

The geomagnetic field is expected to be quiet to unsettled on July 28-30 due to coronal hole effects.

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 higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) 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 polarity overlay		Comment
		SWPC	STAR SDO			SWPC	STAR	Current	Previous
11259	2011.07.17 2011.07.18			N25W50						plage
S1127	2011.07.22		1	N05W21	0000		AXX
S1129	2011.07.23			N11W20						plage
S1130	2011.07.23			N27W26						plage
S1131	2011.07.23		2	S17W20	0000		BXO
S1132	2011.07.23			S17W34						plage
11260	2011.07.24	15	31	N18E30	0110	DSI	EAC			beta-gamma-delta location: N18E32 area: 0230
11262	2011.07.24 2011.07.27	4	6	N16W38	0020	DSO	CRO			beta-gamma formerly region S1133
11261	2011.07.25 2011.07.26	5	19	N15E60	0250	DKO	DKC			area: 0500 location: N15E63
S1135	2011.07.26			S23E62						plage
S1136	2011.07.26			S28E57						plage
S1137	2011.07.26			N07E04						plage
S1138	2011.07.27		6	S33E65	0030		DRI			delta
S1141	2011.07.27		4	N16E00	0010		AXX
S1142	2011.07.27		2	S17E58	0000		BXO
S1143	2011.07.27		6	N17E83	0300		DSC
S1144	2011.07.27		1	S18W57	0000		AXX
Total spot count:		24	78
Sunspot number:		54	178	(raw spot count + 10 * number of spotted regions)
Classification adjusted SN:		44	104	(Sum of raw spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number):		32	59	k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO

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) Month average to date.
3) Running average based on the preliminary daily SWPC ap indices. Values in red are based on the official NGDC ap indices.

This report has been prepared by Jan Alvestad. It is based on 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.