Solar Terrestrial Activity Report

Last major update issued on May 24, 2014 at 06:30 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, 2014)] [Cycle 24 progress (last update May 1, 2014) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 1, 2014)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 1, 2014)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 1, 2014)]

[POES auroral activity level October 2009 - December 2012]
[Solar polar fields vs solar cycles - updated April 17, 2014]
[Presentations: 3rd SSN Workshop, Tucson, 2013 (pdf) / 4th SSN Workshop, Locarno, 2014]

Recent activity

The geomagnetic field was quiet to minor storm on May 23. Solar wind speed at SOHO ranged between 344 and 556 km/s. A disturbance arrived near 05h UTC, however, early on the interplanetary magnetic field was northwards. From 14:30 to 21:30 the IMF was moderately southwards and this caused a significant increase in geomagnetic activity with active and minor storm conditions recorded towards the end of the day. At the onset of the disturbance solar wind speed increased quickly while density decreased.

Solar flux at 20h UTC on 2.8 GHz was 116.3 (decreasing 4.4 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 146.8. The Potsdam WDC planetary A index was 16 (STAR Ap - based on the mean of three hour interval ap indices: 16.3). Three hour interval K indices: 32101345 (planetary), 43112434 (Boulder).

The background x-ray flux is at the class B3 level.

At the time of counting spots (see image time), spots were observed in 13 active regions in 2K resolution (SN: 231) and 9 active regions in 1K resolution (SN: 146) SDO images on the visible solar disk.

Region 12061 [S24W86] was quiet and stable.
Region 12065 [S17W45] developed significantly and a small magnetic delta structure has formed in the northernmost penumbra. Further C class flaring is likely and there is a chance of a minor M class event.
Region 12069 [S17W13] reemerged with a penumbra spot.
Region 12071 [S11E23] gained spots and was quiet.
Region 12072 [S18W30] was quiet and stable.
Region 12073 [S10E37] was quiet and stable.
New region 12074 [S13W33] emerged on May 22 and developed further on May 23 when it was numbered by SWPC.
New region 12075 [S10E78] rotated into view.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3444 [S24W06] reemerged with a penumbra spot.
S3446 [N03W37] reemerged with a penumbra spot.
S3460 [S12E43] developed further and could produce C flares.
S3461 [S18W53] decayed slowly and quietly.
New region S3462 [N24W29] emerged with a penumbra spot.

C2+ Flares (SDO/EVE):

Coronal mass ejections (CMEs)

May 21-23: No obviously Earth directed CMEs were observed in LASCO and 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 small trans equatorial coronal hole (CH618) was in an Earth facing position on May 21.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair to good.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 24 and quiet on May 25-26.

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: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% 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	Magnetic (SDO)				SWPC	STAR	Current	Previous
			2K	1K
12061	2014.05.10 2014.05.11	1	1	1	S25W88	0060	HSX	HSX			area: 0140
S3422	2014.05.13				S23W55						plage
12063	2014.05.13 2014.05.14				N09W81						plage
12065	2014.05.14 2014.05.15	9	17	12	S18W46	0010	DAO	DRI			beta-gamma-delta area: 0070
S3436	2014.05.15				N08W56						plage
S3437	2014.05.15				N25W36						plage
12068	2014.05.16 2014.05.17				S15W57						plage
S3444	2014.05.17		1	1	S24W06	0004		AXX
12069	2014.05.17 2014.05.18		1		S19W15	0002		AXX			location: S17W13
S3446	2014.05.17		1		N03W37	0001
S3448	2014.05.17				S35W50						plage
S3449	2014.05.18				N26W39						plage
12071	2014.05.19	17	26	12	S12E21	0120	DAI	DAI			area: 0180
12072	2014.05.20	1	4	2	S14W34	0000	AXX	BXO			SWPC has essentially duplicated the location of AR 12074, correct location: S18W30 area: 0010
12073	2014.05.20 2014.05.21	5	3	1	S12E39	0070	DSO	CSO			area: 0090 location: S10E37 SWPC incorrectly includes new region S3460 in 12073
S3457	2014.05.20				N20W46						plage
12074	2014.05.22 2014.05.23	8	20	14	S14W33	0030	DRO	DRI			area: 0100
S3460	2014.05.22		24	12	S12E43	0110		DAI
S3461	2014.05.22		1		S17W45	0001		AXX
12075	2014.05.23	1	1	1	S11E78	0030	HAX	HSX			location: S10E78 area: 0100
S3462	2014.05.23		1		N24W29	0001		AXX
Total spot count:		42	101	56
Sunspot number:		112	231	146	(total spot count + 10 * number of spotted regions)
Weighted SN:		70	132	87	(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):		67	81	80	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for MSN 2K, k = 0.55 for MSN 1K (MSN=Magnetic Sunspot Number)

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 WDC-SILSO 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 GFZ Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on the 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.