Solar Terrestrial Activity Report

Last major update issued on July 30, 2011 at 06:50 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 since October 2009 - updated July 29, 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 29. Solar wind speed ranged between 276 and 349 km/s. A weak disturbance was observed beginning at ACE near 13h UTC. Only a minor increase in geomagnetic activity was observed for the remainder of the day. The source of the disturbance is uncertain and may have been a low speed coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 111.7 (increasing 26.1 over the last solar rotation). The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.3). Three hour interval K indices: 11002221 (planetary), 11003211 (Boulder).

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

At midnight UTC the visible solar disk had 6 spotted regions.

Region 11260 appeared to be maturing as the leading penumbra became large and symmetrical. Decay was observed elsewhere in the region. Polarities are still mixed and there's a weak magnetic delta structure in the southeastern part of the main penumbra. Although the region was much quieter than on the previous day, M class flares are still possible. Flares: C4.1 at 01:06, C1.1 at 05:33 UTC.
Region 11261 developed with many new spots emerging and a magnetic delta structure forming. Further M class flares are possible. Flares:  C2.3 at 00:39,  C1.0 at 02:24, C1.2 at 03:48, C1.1 at 04:35, C1.1 at 06:20, C1.4 at 08:07, C1.1 at 08:37, C3.9 at 12:17, C6.3/1F at 16:40, C3.2 at 18:02 UTC. The region was the source of a major, impulsive M9.3 flare at 02:09 on July 30. No CME was observed after the event.
Region 11263 did not change significantly and remains capable of producing an M class flare. Flare: C1.3 at 13:51 UTC

Spotted regions not numbered by NOAA/SWPC:
[S1141] emerged in the northeastern quadrant on July 27. Location at midnight: N18W27
[S1146] emerged in the southeastern quadrant on July 29. Location at midnight: S22E17
[S1147] emerged in the southwestern quadrant on July 29. Location at midnight: S24W17

Coronal mass ejections (CMEs)

July 27-29: 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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on July 30 - August 1. If the stream from CH468 arrives there will likely be some unsettled and active intervals on July 30-31.

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			N25W78						plage
S1127	2011.07.22			N05W46						plage
S1129	2011.07.23			N11W46						plage
S1130	2011.07.23			N27W52						plage
S1131	2011.07.23			S17W46						plage
11260	2011.07.24	20	27	N19E03	0310	EAI	EHI			beta-gamma-delta area: 0400
11262	2011.07.24 2011.07.27			N16W63						plage
11261	2011.07.25 2011.07.26	21	57	N16E33	0300	DAI	DAC			beta-gamma-delta area: 0400 location: N15E35
S1135	2011.07.26			S23E36						plage
S1136	2011.07.26			S28E31						plage
S1137	2011.07.26			N07W22						plage
11264	2011.07.27 2011.07.28	2		S32E37	0010	BXO				plage
S1141	2011.07.27		5	N18W27	0010		AXX
S1142	2011.07.27			S17E32						plage
11263	2011.07.27 2011.07.28	5	8	N18E59	0310	DHO	DKC			beta-delta location: N16E61 area: 0550
S1145	2011.07.28			N30W33						plage
S1146	2011.07.29		1	S22E17	0000		AXX
S1147	2011.07.29		1	S24W17	0000		AXX
Total spot count:		48	99
Sunspot number:		88	159	(raw spot count + 10 * number of spotted regions)
Classification adjusted SN:		68	124	(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):		53	52	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.