Solar Terrestrial Activity Report

Last major update issued on August 4, 2011 at 06:15 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 very quiet on August 3. Solar wind speed ranged between 317 and 366 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 119.9 (increasing 34.4 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.8). Three hour interval K indices: 10001111 (planetary), 10012311 (Boulder).

The background x-ray flux is at the class B6 level.

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

Region 11260 was quiet and stable.
Region 11261 has a strong magnetic delta structure in the central penumbra. An elongated negative polarity umbra has positive polarity neighboring spots both to the north and south. There's virtually no umbral separation in the northernpart of the magnetic delta, thus creating very strong gradients. As long as this structure remains the region will continue to produce major flares. Flares:  M1.1 long duration event peaking at 03:37, C1.1 at 06:46, C8.7 at 07:58, C1.0 at 10:04, major long duration M6.0/2B event peaking at 13:48 (associated with type II and IV radio sweeps and an Earth directed CME), C8.5 at 19:30. The region was the source of a major M9.3 event at 03:57 UTC on August 4 (associated with a fast full halo CME).
Region 11263 changed with the leader spot becoming the largest spot as the trailing penumbra fragmented into smaller penumbrae. There's still a magnetic delta structure in a trailing penumbra. A major flare is possible. Flares: M1.7/1F at 04:32, C2.3 at 19:00 UTC

Spotted regions not numbered by NOAA/SWPC:
[S1148] emerged in the northeast quadrant on August 2. Slow development was observed in August 3. Location at midnight: N17E53
[S1151] emerged in the southwest quadrant on August 3. Location at midnight: S19W53
[S1152] emerged in the southeast quadrant on August 3. Location at midnight: S07E66

Coronal mass ejections (CMEs)

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.
August 3: A full halo CME was observed in LASCO and STEREO images following the M6 event in region 11261 at 13:48 UTC. The CME coudl reach Earth on August 5.

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) trans equatorial coronal hole will be in an Earth facing position on August 3-4. A poorly defined coronal hole (CH470) was Earth facing on August 2-3.

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 initially quiet on August 4. A CME impact is likely during the latter half of the day with a possibility of active to major storm conditions. Another CME impact is likely on August 5 (related to M6 flare). A large CME associated with the M9 event on August 4 will likely reach Earth on August 6 and cause active to major geomagnetic storming.

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	5	9	N18W62	0200	CSO	CHO			location: N19W66 area: 0290
11261	2011.07.25 2011.07.26	15	35	N16W37	0300	DKI	DAC			beta-gamma-delta location: N15W36 area: 0450
S1136	2011.07.26			S24W30						plage
11264	2011.07.27 2011.07.28			S23W35						plage location: S33W25
S1142	2011.07.27			S17W33						plage
11263	2011.07.27 2011.07.28	16	28	N17W06	0600	DKI	DHC			beta-gamma-delta
S1146	2011.07.29			S22W48						plage
S1148	2011.08.02		4	N17E53	0010		CRO
S1151	2011.08.03		1	S19W53	0000		AXX
S1152	2011.08.03		1	S07E66	0000		AXX
Total spot count:		36	78
Sunspot number:		66	138	(raw spot count + 10 * number of spotted regions)
Classification adjusted SN:		61	106	(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):		40	46	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.