Solar Terrestrial Activity Report

Last major update issued on May 16, 2013 at 04:45 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update May 1, 2013)] [Cycle 24 progress (last update April 7, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 6, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated May 12, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to active on May 15. Solar wind speed at SOHO ranged between 331 and 501 km/s. A sudden increase in solar wind speed was observed at SOHO at 07:50 UTC, probably the arrival of a transient associated with a CME.

Solar flux measured at 20h UTC on 2.8 GHz was 145.6 (increasing 47.2 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.0). Three hour interval K indices: 11224221 (planetary), 11233322 (Boulder).

The background x-ray flux was at the class B5 level.

At 15h UTC the visible solar disk had 16 spotted active regions (in 2K resolution SDO images).

Region 11741 [S21W53] was quiet and stable.
Region 11742 [N30W27] decayed slowly and quietly and could become spotless today.
Region 11743 [N21W26] decayed slowly and was quiet.
Region 11744 [N04W09] was quiet and stable.
Region 11745 [N12E13] has many penumbra spots in addition to a large penumbral structure.
Region 11746 [S28E13] developed slightly and was quiet.
Region 11747 [S18E07] was quiet and stable.
Region 11748 [N11E53] is a compact region which has a magnetic delta structure in the leading spot section. Further M and X class flaring is possible. C5+ flares: X1.2/2N long duration event peaking at 01:44 UTC, this event was asociated with an asymmetrical full halo CME.
New region 11749 [S23W28] emerged on May 13 and was numbered by SWPC 2 days later.
New region 11750 [S11W12] emerged on May 14 and got its NOAA number the following day.
New region 11751 [S24E24] emerged on May 12 and was noticed by SWPC 3 days later.

Spotted regions not numbered by SWPC:
S2415 [S24W13] reemerged with a penumbra spot.
S2419 [S15E50] was quiet and stable.
New region S2420 [S13E02] emerged with penumbra spots.
New region S2421 [S17W03] emerged with penumbra spots.
New region S2422 [S17W18] emerged with a penumbra spot.

Due to SDO image processing problems at NASA, the following SDO/AIA 4500 image at 23h UTC has been used to display the emergence of new region AR S2423 in the northern hemisphere close to the long axis stretching from AR 11742 to AR 11746.

Coronal mass ejections (CMEs)

May 13: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
May 14: At least a partial halo CME was observed after the X3 event in AR 11748. The CME was fast and Earth could see a flanking impact on May 16.
May 15: A wide CME was observed after the X1 event in AR 11748. A flanking impact is possible on May 17.

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 poorly defined trans equatorial coronal hole (CH570) was in an Earth facing position on May 13.

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 unsettled to minor storm on May 16-17 due to CME effects and quiet to active on May 18.

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 2K resolution) Compare to the previous day's image. 0.5k image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue 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
11740	2013.05.03				S21W81						plage
11741	2013.05.05 2013.05.06		1		S21W57	0002		AXX			location: S21W53
11742	2013.05.07 2013.05.09		2		N28W31	0004		BXO			location: N30W27
11743	2013.05.08 2013.05.09	5	8	4	N21W28	0090	DAO	DSO
11744	2013.05.08 2013.05.09	23	45	13	N05W12	0070	CAO	DAO			beta-gamma
S2406	2013.05.08				N12W57						plage
11745	2013.05.10	28	50	10	N13E12	0390	EKC	EKO			beta-gamma
11746	2013.05.10 2013.05.11	8	12	8	S27E14	0250	CSO	DSO			area: 0320
S2410	2013.05.11				N08W50						plage
11747	2013.05.12	11	21	10	S18E09	0090	CAO	CSI			area: 0140
11751	2013.05.12 2013.05.15	3	10	5	S23E23	0010	BXO	CRO
S2412	2013.05.12				S44W12						plage
11748	2013.05.13	9	23	12	N11E53	0260	DKI	DAC			beta-gamma-delta location: N11E53
S2414	2013.05.13				N20W14						plage
S2415	2013.05.13		1		S24W13	0001		AXX
11749	2013.05.13 2013.05.15	6	8	4	S23W40	0010	BXO	BXO
11750	2013.05.14 2013.05.15	3	9	4	S11W13	0010	BXO	DRO			area: 0030
S2418	2013.05.14				S43E04						plage
S2419	2013.05.14		1		S15E50	0002		AXX
S2420	2013.05.15		7	5	S13E02	0030		BXO
S2421	2013.05.15		2	1	S17W03	0006		BXO
S2422	2013.05.15		1		S17W18	0002		AXX
Total spot count:		96	201	76
Sunspot number:		186	361	186	(total spot count + 10 * number of spotted regions)
Weighted SN:		136	242	117	(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):		112	126	102	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 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) Boulder SN current month average to date. 2C) STAR SDO 1K Wolf number 30 day average.
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.