Solar Terrestrial Activity Report

Last major update issued on October 28, 2011 at 04:30 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 27, 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 27. Solar wind speed ranged between 356 and 474 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 131.5 (decreasing 6.6 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.0). Three hour interval K indices: 12211101 (planetary), 13212211 (Boulder).

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

At midnight UTC the visible solar disk had 9 spotted regions (in 2K resolution SDO images).

Region 11324 [N12W47] began to develop again after several days of decay.
Region 11325 [N16W26] decayed slowly and quietly.
Region 11327 [S22W79] decayed as it rotated to the southwest limb.
Region 11330 [N07E04] was quiet. The trailing penumbra fragmented and the region appears to be decaying.
Region 11332 [N32E37] was quiet and stable.
New region 11333 [N15E12] emerged on October 23 and got the attention of SWPC 4 days later. The region developed polarity intermixing in the central part. Further development could cause a magnetic delta structure to form. C flaring is likely. Flare: C2.6 at 18:44 UTC.

Spotted regions not reported by NOAA/SWPC:
[S1295] emerged in the southeast quadrant on October 25. Location at midnight: S20W03
[S1296] emerged with tiny spots in an old plage area in the northeast quadrant on October 27. Location at midnight: N17E47
[S1297] emerged to the northeast of region 11327 on October 27. Location at midnight: S17W62

A filament eruption to the north of region 11330 began at approximately 11:13 UTC on October 27 and caused a small, potentially geoeffective CME. The CME was best defined off the northeast limb in LASCO images, faint elsewhere.

Coronal mass ejections (CMEs)

October 25-26: No obviously Earth directed CMEs observed.
October 27: A small, faint halo CME was observed after noon following a filament eruption to the north of region 11330.

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 coronal hole (CH481)  in the southern hemisphere was in an Earth facing position on October 25-26.

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 28. A high speed stream from CH481 could cause quiet to unsettled conditions from late on October 28 and on October 29.

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
11323	2011.10.16 2011.10.17			N25W81						plage
11324	2011.10.17	3	19	N12W52	0050	CSO	DRO
11327	2011.10.17 2011.10.20	1	3	S20W81	0060	HSX	HRX			location: S22W79 area: 0020
11325	2011.10.19	1	10	N17W26	0010	AXX	CRO
11328	2011.10.20			N17W76
11330	2011.10.21 2011.10.22	9	32	N08E05	0460	EKO	FHO			area: 0650
S1289	2011.10.22			N20W48						plage
11333	2011.10.23 2011.10.27	10	18	N16E12	0090	DAI	DRI
11332	2011.10.23 2011.10.24	1	4	N31E35	0030	HAX	HSX
S1294	2011.10.23			N27W29						plage
S1295	2011.10.25		1	S20W03	0000		AXX
S1296	2011.10.27		2	N17E47	0000		AXX
S1297	2011.10.27		1	S17W62	0000		AXX
Total spot count:		25	90
Sunspot number:		85	180	(total spot count + 10 * number of spotted regions)
Classification adjusted SN:		55	117	(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):		51	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.