Solar Terrestrial Activity Report

Last major update issued on May 8, 2012 at 04:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 3, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 3, 2012)]

[POES auroral activity level since October 2009 - updated May 5, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on May 7. Solar wind speed at SOHO ranged between 283 and 302 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 121.7 (increasing 28.4 over the last solar rotation). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.3). Three hour interval K indices: 01121100 (planetary), 01122211 (Boulder).

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

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

Region 11470 [S17W52] decayed slowly and quietly.
Region 11471 [S22W49] decayed slowly. Flare: M1.9/1N at 14:31 UTC. This event was associated with a minor CME which may have had an Earth directed component.
Region 11474 [N13E02] decayed slowly and quietly.
Region 11475 [N03E10] decayed and could soon become spotless.
Region 11476 [N11E47] is a complex region with at least 3 several magnetic delta structures (a weak one in the southern part of the huge penumbra, a stronger one in a penumbra to the northeast of the leading penumbra and one in a northeastern central penumbra). A major flare is possible. Flares: C7.1 at 02:50, C7.9 at 11:08, C7.4 at 17:26 UTC and a number of smaller events.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
S1633 [N12E25] has a single tiny spot.
New region S1634 [S22E84] rotated into view at the southeast limb revealing a single symmetrical penumbra.

Coronal mass ejections (CMEs)

May 5-6: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. There's a slight chance one or two of the small CMEs observed on May 4 and 5 could have Earth directed components.
May 7: The M1.9 event in region 11471 may have had a weak Earth directed component. The most interesting CME of the day was observed after a filament erupted in the southeast quadrant  beginning near 21:15 UTC. STEREO-B displays a CME late on May 7 and early on May 8 which could easily be Earth directed, neither STEREO-A nor LASCO imagery from the relevant time is currently available.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent trans equatorial coronal hole (CH515) was in an Earth facing position on May 5-7. Another recurrent trans equatorial coronal hole (CH516) could become Earth facing on May 9-10.

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, 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 this method, the extent and intensity of both CHs 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 fair to good. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet initially on May 8. Late in the day or on May 9 a high speed stream associated with CH515 will likely arrive and cause unsettled to minor storm conditions until May 10, there's a chance of isolated major storm intervals. The CME observed late on May 7 could reach Earth on May 10 and contribute to the ongoing disturbance.

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 magnetic polarity overlay		Comment
		SWPC	STAR SDO				SWPC	STAR	Current	Previous
			2K	1K
11471	2012.04.27 2012.04.28	8	11	5	S19W50	0210	DSO	CSO			location: S22W49
11470	2012.04.27 2012.04.28	5	3	2	S15W57	0030	CRO	AXX			location: S17W52
S1618	2012.04.28				N21W51						plage
11472	2012.04.29				S28W66						plage location: S30W58
11474	2012.05.01 2012.05.02	1	5	2	N13E03	0000	AXX	CRO
11475	2012.05.02		2		N05E10	0000		AXX
S1626	2012.05.02				S28W41						plage
11476	2012.05.04 2012.05.05	25	69	38	N10E48	0810	FKC	FKC			beta-gamma-delta area: 1100 location: N11E47
S1629	2012.05.04				S16W13						plage
S1630	2012.05.04				N27W30						plage
S1631	2012.05.04				S24E14						plage
S1633	2012.05.06		1		N12E25	0000		AXX
S1634	2012.05.07		1	1	S22E84	0100		HSX
Total spot count:		39	92	48
Sunspot number:		79	162	98	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		57	115	71	(Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number):		47	57	54	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

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 quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC 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.