Solar Terrestrial Activity Report

Last major update issued on October 12, 2011 at 04:20 UTC. Minor update posted at 15:10 UTC.

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

[POES auroral activity level since October 2009 - updated October 10, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2113 [July-August 2011] - 2114 [August-September 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on October 11. Solar wind speed ranged between 304 and 372 km/s.

Solar flux measured at 23h UTC on 2.8 GHz was 130.1 (decreasing 12.5 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.9). Three hour interval K indices: 00102211 (planetary), 00101321 (Boulder).

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

At midnight UTC the visible solar disk had 10 spotted regions (in 2K resolution SDO images).

Region 11309 [N23W49] decayed slowly and quietly.
Region 11311 [S12W77] rotated quietly to the southwest limb.
Region 11312 [N23W15] was quiet and stable.
Region 11313 [S14W12] has minor polarity intermixing, however, opposite polarity spots are not closely spaced and the region was quiet.
Region 11314 [N27E48] was quiet and mostly unchanged. There's a small chance of a major flare.
Region 11315 [N20W05] decayed quickly and was quiet.
New region 11316 [S12E57] emerged near the southeast limb on October 10 and was numbered the next day by SWPC. The region developed fairly quickly and is currently the most complex region on the visible disk. There's a weak magnetic delta structure at the eastern edge of the main penumbra and some polarity intermixing elsewhere in this fairly compact region. Further C flares are possible and if the region develops further there'll be a chance of minor M class flares. Flare: C1.1 at 23:23 UTC.
New region 11317 [S26E68] rotated into view at the southeast limb on October 10 and was assigned a number by SWPC the following day.

Spotted regions not reported by NOAA/SWPC:
[S1267] emerged near the northeast limb on October 10 and developed on October 11. The region has polarity intermixing. Location at midnight: N10E57
[S1270] emerged in the northeast quadrant on October 11. Polarities are intermixed. Location at midnight: N22E10

Minor update added at 15:10 UTC on October 12: Regions 11316 and S1267 have developed further with both becoming capable of producing minor M class flares. Flare activity has increased significantly today because of the development in these two regions. The latest high resolution CHARMAP.

Coronal mass ejections (CMEs)

October 9-11: No obviously Earth directed CMEs 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 trans equatorial coronal hole (CH479) will rotate into an Earth facing position on October 12-13.

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 to fair.

Forecast

The geomagnetic field is expected to be quiet on October 12-14. Quiet to active with a chance of minor storm intervals is possible on October 15-16 due to effects from CH479.

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
11308	2011.09.30 2011.10.01			S25W83						plage
11309	2011.10.01 2011.10.02	1	2	N23W51	0040	HSX	HSX			area: 0080 location: N23W49
S1251	2011.10.03			S20W46						plage
11311	2011.10.03 2011.10.04	1	1	S12W77	0030	HSX	AXX			area: 0000
11312	2011.10.03 2011.10.04	1	4	N22W16	0210	HSX	CHO			area: 0320 location: N23W15
11313	2011.10.04 2011.10.05	18	30	S15W13	0120	DAI	EAI			beta-gamma location: S14W12
S1255	2011.10.06			S14W39						plage
S1257	2011.10.07			N11E20						plage
S1258	2011.10.07			S26W30						plage
S1259	2011.10.07			N19W36						plage
11314	2011.10.08 2011.10.09	2	3	N27E45	0250	CHO	CHO			area: 0450 location: N27E48
11315	2011.10.09 2011.10.10	6	8	N20W06	0040	DAO	CRO			area: 0020
S1264	2011.10.09			N33W09						plage
11317	2011.10.10 2011.10.11	1	1	S26E68	0090	HSX	HSX			formerly region S1265
11316	2011.10.10 2011.10.11	3	14	S12E56	0060	DAI	DSI			beta-gamma-delta formerly region S1266 area: 0140
S1267	2011.10.10		7	N10E57	0030		CRO			beta-gamma
S1268	2011.10.10			N18E55
S1269	2011.10.10			N18W22						plage
S1270	2011.10.11		6	N22E10	0010		BXO			beta-gamma
Total spot count:		33	76
Sunspot number:		113	176	(total spot count + 10 * number of spotted regions)
Classification adjusted SN:		78	122	(Sum of total spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number):		68	58	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.