Solar Terrestrial Activity Report

Last major update issued on October 27, 2011 at 02:30 UTC. Minor update posted at 17:35 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 24, 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 very quiet on October 26. Solar wind speed ranged between 363 and 527 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 132.2 (decreasing 4.4 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.1). Three hour interval K indices: 10001111 (planetary), 21102211 (Boulder).

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

At midnight UTC the visible solar disk had 7 spotted regions (in 2K resolution SDO images).

Region 11324 [N12W37] decayed further and was mostly quiet. Flare: C1.2 at 10:01 UTC
Region 11325 [N16W14] decayed slowly and quietly.
Region 11327 [S22W65] was quiet with the main penumbra fragmenting.
Region 11330 [N08E17] was quiet and has M class flaring potential. There's minor polarity intermixing near the leading penumbra.
Region 11332 [N31E49] was quiet and stable.

Spotted regions not reported by NOAA/SWPC:
[S1292] emerged just north of region 11330 on October 23 and has since then developed very slowly. Location at midnight: N16E24
[S1295] emerged in the southeast quadrant on October 25 and developed slowly on October 26. Location at midnight: S21E10

Minor update posted at 17:35 UTC on October 27: A filament eruption to the north of region 11330 began at approximately 11:13 UTC today and cause a potentially geoeffective CME. The CME could reach Earth on October 30 and cause unsettled to active conditions.

Region S1292 has developed significantly today and could produce C flares.

Coronal mass ejections (CMEs)

October 24-26: 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 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. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet on October 27. A high speed stream from CH481 could cause quiet to unsettled conditions on October 28-29.

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			N25W67						plage
11324	2011.10.17	16	16	N12W38	0030	DSO	BXO			area: 0010
11327	2011.10.17 2011.10.20	3	6	S20W67	0060	CSO	CAO			location: S22W65
11325	2011.10.19	6	15	N17W12	0030	CSO	CSO			location: N16W14
11328	2011.10.20			N17W62
11330	2011.10.21 2011.10.22	15	22	N09E18	0500	EKO	FHO			area: 0750
S1288	2011.10.22			S15W44						plage
S1289	2011.10.22			N20W35						plage
S1290	2011.10.22			N17W47						plage
S1292	2011.10.23		8	N16E24	0010		BXO
11332	2011.10.23 2011.10.24	1	2	N31E49	0040	HSX	HSX
S1294	2011.10.23			N27W16						plage
S1295	2011.10.25		3	S21E10	0010		BXO
Total spot count:		41	72
Sunspot number:		91	142	(total spot count + 10 * number of spotted regions)
Classification adjusted SN:		71	97	(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):		55	47	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.