Solar Terrestrial Activity Report

Last major update issued on August 3, 2011 at 05:45 UTC. Minor update posted at 17:20 UTC

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

[POES auroral activity level since October 2009 - updated August 2, 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 August 2. Solar wind speed ranged between 356 and 516 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 121.6 (increasing 37.0 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.4). Three hour interval K indices: 21001101 (planetary), 21111211 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight UTC the visible solar disk had 7 spotted regions.

Region 11260 decayed slowly and quietly.
Region 11261 lost many small spots, however, the main penumbrae are magnetically complex and contain significant delta structures. A major proton event is possible. Flares:  long duration M1.4/1N peaking at 06:19 (associated with type II and IV radio sweeps and an Earth directed CME), C2.0 at 09:27, C1.1 at 17:23 UTC. The region was the source of a long duration M1.1 event peaking at 03:37 UTC on August 3.
Region 11263 developed further and has a complex trailing penumbra with 2 magnetic delta structures. Major flares are possible. Flare: C1.2 at 03:14, C1.2 at 04:00, C2.0 at 11:39 UTC. This region was the source of an M1.7 impulsive flare at 04:32 UTC on August 3.
Region 11264 reemerged with a couple of spots.
Region 11265 rotated quietly to the northwest limb.

Spotted regions not numbered by NOAA/SWPC:
[S1136] reemerged with several spots on July 30 and decayed slowly on August 2. Location at midnight: S24W17
[S1148] emerged in the northeast quadrant on August 2. Location at midnight: N18E68

Minor update added at 14:30 UTC on August 3: Region 11261 produced a major M6.0 long duration event peaking at 13:48 UTC. What appears to be another earthbound CME was visible as early as 13:55 UTC in STEREO images.

Minor update added at 17:20 UTC: The main magnetic delta structure in region 11261 has very strong gradients with the opposite polarity umbrae hard to separate visually. The CME produced earlier today was full halo and could reach Earth on August 5. The latest high resolution CHARMAP.

Coronal mass ejections (CMEs)

July 31 - August 1: No obviously earth directed CMEs were observed.
August 2: An Earth directed CME was observed in LASCO and STEREO images after the LDE in region 11261 peaking at 06:19 UTC. This CME will likely reach Earth sometime after 09h UTC on August 4.

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 recurrent coronal hole (CH469) in the southern hemisphere could rotate into an Earth facing position on August 3-4.

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 on August 3. On August 4 a CME impact is likely and could cause active to major storm conditions that day and on August 5.

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
11260	2011.07.24	7	10	N19W49	0300	EHO	CHO			location: N18W51
11261	2011.07.25 2011.07.26	25	40	N15W21	0390	FKC	DKC			beta-gamma-delta location: N16W22 area: 0450
S1136	2011.07.26		2	S24W17	0000		AXX
11264	2011.07.27 2011.07.28		2	S23W21	0000		BXO			location: S33W12
11265	2011.07.27 2011.07.30	1	1	N16W80	0005	AXX	AXX
S1142	2011.07.27			S17W20						plage
11263	2011.07.27 2011.07.28	25	33	N17E08	0560	EKI	EKC			beta-gamma-delta area: 0800
S1146	2011.07.29			S22W35						plage
S1148	2011.08.02		1	N18E68	0000		AXX
Total spot count:		58	89
Sunspot number:		98	159	(raw spot count + 10 * number of spotted regions)
Classification adjusted SN:		88	119	(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):		59	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.