Solar Terrestrial Activity Report

Last major update issued on April 5, 2014 at 06:20 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 on April 4. Solar wind speed at SOHO ranged between 367 and 467 km/s. ACE EPAM data indicate that a CME arrived during the day, sometime after noon, probably the CME observed on April 1. No solar wind shock was observed and there was no significant increase in geomagnetic activity. The CME observed on April 2 has not yet arrived.

Solar flux at 20h UTC on 2.8 GHz was 156.9 (increasing 15.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 154.5. The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 11222210 (planetary), 11223321 (Boulder).

The background x-ray flux is at the class B4 level.

At the time of counting spots (see image time), spots were observed in 12 active regions in 2K resolution (SN: 338) and 11 active regions in 1K resolution (SN: 220) SDO images on the visible solar disk.

Region 12021 [S13W41] developed a magnetic delta structure in the largest penumbral structure. M flares are possible. C5+ flare: C6.2 at 14:54 UTC.
Region 12022 [N17W27] was quiet and stable.
Region 12026 [S11E14] was mostly quiet and stable with some decay observed in the leading and central spots sections. C and M class flares are possible.
Region 12027 [N12E18] was mostly unchanged. C5+ flare: C8.3/1F at 13:48 UTC. This flare was associated with a fairly narrow CME off the northeast limb.
Region 12028 [S08E23] was quiet and stable.
Region 12029 [N17E02] decayed slowly and quietly.
Region 12030 [N10E31] developed gaining many spots. The region has polarity intermixing and could produce C and minor M class flares.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3288 [N06E15] lost the leader spots.
S3297 [N07W43] lost the trailing spots and was quiet.
S3298 [N08E18] was quiet and stable.
New region S3301 [N14E66] emerged with a penumbra spot.
New region S3302 [S19E39] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

April 2: A large and fast asymmetrical full halo CME was observed after the M6.5 event in AR 12027.
April 3-4: 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

No obvious coronal holes are currently in or near potentially geoeffective positions.

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 quiet to active on April 5 due to CME effects and quiet on April 6-7.

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
12020	2014.03.24 2014.03.27				S13W81
S3267	2014.03.26				S22W59						plage
12022	2014.03.27 2014.03.28	2	5	3	N17W31	0010	HRX	CRO			area: 0020 location: N17W27
12025	2014.03.27 2014.03.30				S24W89						plage location: S20W82
12021	2014.03.28	29	53	24	S13W44	0320	DKC	DKC			area: 0460 location: S13W41
12024	2014.03.28 2014.03.29				N17W65						plage
S3276	2014.03.28				S12W49						plage
S3277	2014.03.28				S27W39						plage
12026	2014.03.30	27	68	38	S11E11	0390	EKC	EKI			location: S11E14
12027	2014.03.30 2014.03.31	5	13	6	N11E17	0150	CAO	CAO			area: 0230 location: N12E18
S3288	2014.03.31		2	1	N06E15	0007		AXX
12028	2014.03.31 2014.04.01	5	13	8	S09W23	0010	BXO	CRO
S3290	2014.03.31				S20W10						plage
12029	2014.04.01	5	8	3	N17E02	0070	DAO	DAO			area: 0110
12030	2014.04.01	16	41	22	N11E30	0100	DAI	EAC			beta-gamma area: 0240
S3295	2014.04.02				S11W17						plage
S3296	2014.04.02				S01W15						plage
S3297	2014.04.02		5	3	N07W43	0020		AXX
S3298	2014.04.03		5	2	N08E18	0013		CRO
S3299	2014.04.03				N13W18						plage
S3300	2014.04.03				S13E60						plage
S3301	2014.04.04		1		N14E66	0002		AXX
S3302	2014.04.04		1	1	S19E39	0005		AXX
Total spot count:		89	218	110
Sunspot number:		159	338	220	(total spot count + 10 * number of spotted regions)
Weighted SN:		124	272	154	(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):		95	118	121	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.