Solar Terrestrial Activity Report

Last major update issued on May 10, 2012 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 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 unsettled to minor storm on May 9. Solar wind speed at SOHO ranged between 420 and 584 km/s under the influence of a high speed stream from CH515.

Solar flux measured at 20h UTC on 2.8 GHz was 127.3 (increasing 32.0 over the last solar rotation). The Potsdam WDC planetary A index was 35 (STAR Ap - based on the mean of three hour interval ap indices: 35.0). Three hour interval K indices: 45434455 (planetary), 44434344 (Boulder).

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

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

Region 11471 [S22W78] decayed slowly and quietly.
Region 11474 [N17W16] decayed slowly and quietly.
Region 11476 [N10E19] has magnetic delta structures in 3 penumbrae with the major delta located in the southern part of the huge leading penumbra. Major flares, even X class flares, are possible. Flares: M4.7/1N at 12:32, M1.8/1B at 14:08, C9.1 at 20:52, M4.1 at 21:05 UTC. A major flare, M5.7, was recorded at 04:18 UTC on May 10.
Region 11477 [S22E60] was quiet and stable. SWPC has chosen to include S1635 in this region.

Spotted active regions not numbered by NOAA/SWPC:
S1635 [S24E69] was quiet and stable.
S1636 [S16E18] developed slowly and quietly.
S1638 [S19W20] was quiet and stable.
S1640 [S16W48] developed slowly and quietly.
New region S1642 [S13E37] emerged with several spots.
New region S1643 [S14W43] emerged to the northeast of AR S1640.

Coronal mass ejections (CMEs)

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.
May 8: A filament eruption beginning at 09:45 UTC near AR 11474 across the central meridian was the source of a small CME observed in both STEREO-A and B imagery after 11h UTC. While most of the ejected material was over the northern limbs, it appears that a part of the CME is Earth directed.
May 9: No obviously Earth directed CMEs were observed in STEREO imagery.

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) will be 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 poor. Propagation on long distance northeast-southwest paths is good.

Forecast

The geomagnetic field is expected to be quiet to active on May 10 due to a high speed stream from CH515 and quiet to unsettled on May 11. The CME observed late on May 7 could reach Earth on May 10 and contribute to the ongoing disturbance. The CME observed on May 8 could reach Earth on May 11. Starting late on May 12 or early on May 13 a high speed stream from CH516 could cause quiet to active conditions until May 14.

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	1	1	1	S21W78	0110	HSX	HSX
11470	2012.04.27 2012.04.28				S19W82						plage location: S17W80
11474	2012.05.01 2012.05.02	1	1	1	N16W23	0010	AXX	AXX			location: N17W16
11475	2012.05.02				N05W20						plage
11476	2012.05.04 2012.05.05	35	100	50	N10E22	1040	FKC	FKC			beta-gamma-delta area: 1400 location: N10E19
S1629	2012.05.04				S16W39						plage
S1630	2012.05.04				N27W56						plage
S1631	2012.05.04				S24W12						plage
S1633	2012.05.06				N12W01						plage
11477	2012.05.07 2012.05.08	2	1	1	S24E62	0150	DSO	HSX			SWPC sees this and S1635 as one group location: S22E60 area: 0090
S1635	2012.05.08		1	1	S24E69	0090		HSX
S1636	2012.05.08		3	3	S16E18	0010		CRO
S1637	2012.05.08				N23W16						plage
S1638	2012.05.08		2	2	S19W20	0010		BXO
S1639	2012.05.08				S16W31						plage
S1640	2012.05.08		3	1	S16W48	0000		BXO
S1641	2012.05.08				N11W40						plage
S1642	2012.05.09		5	4	S13E37	0010		CRO
S1643	2012.05.09		3		S14W43	0000		BXO
Total spot count:		39	120	64
Sunspot number:		79	220	154	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		59	151	95	(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	77	85	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.