Solar Terrestrial Activity Report

Last major update issued on April 12, 2014 at 06:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2014)] [Cycle 24 progress (last update April 1, 2014) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2014)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2014)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 2, 2014)]

[POES auroral activity level October 2009 - December 2012]
[Solar polar fields vs solar cycles - updated March 16, 2014]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to unsettled on April 11. Solar wind speed at SOHO ranged between 345 and 419 km/s. A magnetic cloud embedded within the solar wind began was observed after 07h UTC. The interplanetary magnetic field slowly increased its total field and swung southwards. By the end of the day the IMF was moderately southwards and minor geomagnetic storming was observed early on April 12. The source of the disturbance is uncertain but may be associated with a corotating interaction region caused by a large southern hemisphere coronal hole.

Solar flux at 20h UTC on 2.8 GHz was 137.6 (decreasing 1.4 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 150.8. The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.1). Three hour interval K indices: 01211213 (planetary), 02312322 (Boulder).

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

At the time of counting spots (see image time), spots were observed in 8 active regions in 2K resolution (SN: 155) and 8 active regions in 1K resolution (SN: 119) SDO images on the visible solar disk.

Region 12027 [N13W75] decayed slowly and quietly.
Region 12032 [N10E25] decayed slowly in the trailing spot section, however, there is minor polarity intermixing.
Region 12033 [N11E36] was quiet and stable.
Region 12034 [N04E57] developed further and could produce C and minor M class flares.
New region 12035 [S17E77] rotated partly into view on April 10 and was numbered by SWPC the next day. The region has polarity intermixing and further C class flaring is likely. M class flaring is possible. C5+ flares: C9.4 at 11:24, C5.3 at 15:01 UTC.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3309 [S21W23] was quiet and stable.
S3310 [S15W03] was quiet and stable.
S3311 [S08E15] was quiet and stable.

Coronal mass ejections (CMEs)

April 9-11: 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

An extension of a southern hemisphere coronal hole (CH610) rotated across the central meridian on April 8 but was likely too far to the south to become geoeffective. An extension of a northern hemisphere coronal hole (CH611) was in a potentially geoeffective position on April 10.

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 minor storm on April 12 and quiet on April 13-14. There is a chance of unsettled intervals on April 13 due to possible effects from CH611.

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
12026	2014.03.30	3			S08W85	0010	AXX				spotless
12027	2014.03.30 2014.03.31	5	1	1	N14W76	0100	CSO	HSX			area: 0160
12028	2014.03.31 2014.04.01				S08W69						plage
12030	2014.04.01				N12W62						plage
S3300	2014.04.03				S13W31						plage
S3301	2014.04.04				N14W25						plage
S3302	2014.04.04				S18W56						plage
S3304	2014.04.06				S13W43						plage
S3305	2014.04.06				N11W13						plage
12032	2014.04.07 2014.04.08	7	20	9	N13E26	0160	DSO	DSO			beta-gamma area: 0250 location: N10E25
S3308	2014.04.07				S02W17						plage
S3309	2014.04.07		6	4	S21W23	0025		BXO	images/AR_S3309_20140411_2345.png
S3310	2014.04.08		6	3	S08E15	0013		BXO	images/AR_S3310_20140411_2345.png
12033	2014.04.09	1	3	2	N12E34	0110	HSX	HSX			area: 0160 location: N11E36
S3311	2014.04.09		4	1	S14E16	0014		BXO
12034	2014.04.10	5	19	10	N05E57	0130	DAO	DKI			area: 0330
12035	2014.04.10 2014.04.11	2	16	9	S15E74	0150	DAO	DAC			beta-gamma 'location: S17E77 area: 0200
S3314	2014.04.10				S22W46						plage
Total spot count:		23	75	39
Sunspot number:		83	155	119	(total spot count + 10 * number of spotted regions)
Weighted SN:		48	105	69	(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):		50	54	65	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.