Solar Terrestrial Activity Report

Last major update issued on May 3, 2014 at 06:00 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]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on May 2. Solar wind speed at SOHO ranged between 339 and 419 km/s.

Solar flux at 20h UTC on 2.8 GHz was 135.4 (decreasing 6.7 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 152.2. The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.4). Three hour interval K indices: 12111001 (planetary), 12101211 (Boulder).

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

At the time of counting spots (see image time), spots were observed in 9 active regions in 2K resolution (SN: 208) and 9 active regions in 1K resolution (SN: 167) SDO images on the visible solar disk.

Region 12047 [S17W28] appears to be maturing and produced a few C flares.
Region 12049 [S07E07] matured and was mostly quiet.
Region 12050 [N12E07] was quiet and stable.
Region 12051 [S10W37] developed quickly and has magnetic delta structures in the southern part of the northernmost large penumbra. There's an increasing chance of an M class flare.
New region 12052 [S11E48] emerged on May 1 and was numbered the next day by SWPC. Further C class flaring is possible.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3374 [S09W13] was quiet and stable.
New region S3380 [N10E61] emerged with penumbra spots.
New region S3381 [S18E02] emerged with a penumbra spot.
New region S3382 [S14E30] emerged with a penumbra spot.

C2+ Flares (SDO/EVE):

Coronal mass ejections (CMEs)

May 1-2: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
April 30: A faint CME (likely associated with a filament eruption to the east of AR 12047) was observed early in the day in LASCO C2.

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 coronal hole (CH614) in the northern hemisphere rotated across the central meridian on May 2. A small southern hemisphere coronal hole (CH615) will likely rotate to an Earth facing position on May 4.

Propagation

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

Forecast

The geomagnetic field is expected to be mostly quiet on May 3-4. There's a slight chance a weak CME could reach Earth on May 3 and cause unsettled intervals. On May 5-6 there's a chance of weak effects (unsettled intervals) due to a stream from CH614.

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
S3355	2014.04.24				N18W57						plage
S3358	2014.04.25				S13W49						plage
S3359	2014.04.25				S30W38						plage
12047	2014.04.26	19	34	25	S18W28	0360	DKC	DAC			area: 0380
12049	2014.04.26 2014.04.27	18	30	18	S07W00	0400	EKC	DHC			area: 0550 location: S07E07
12050	2014.04.27	2	7	5	N12E07	0040	HAX	CAO			area: 0060
S3371	2014.04.27				S12W37						plage
S3373	2014.04.27				N13W48						plage
S3374	2014.04.28		3	2	S09W13	0011		BXO
S3375	2014.04.28				S09W25						plage
12051	2014.05.01	16	27	17	S10W37	0180	DAC	DKC			beta-gamma-delta area: 0560
S3377	2014.05.01				N03W16						plage
12052	2014.05.01 2014.05.02	6	13	7	S11E49	0020	CRO	DRI			area: 0070
S3379	2014.05.01				S06E57						plage
S3380	2014.05.02		2	1	N10E61	0006		AXX
S3381	2014.05.02		1	1	S18E02	0005		AXX
S3382	2014.05.02		1	1	S14E30	0003		AXX
Total spot count:		61	118	77
Sunspot number:		111	208	167	(total spot count + 10 * number of spotted regions)
Weighted SN:		94	151	108	(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	73	92	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.