Solar Terrestrial Activity Report

Last major update issued on April 3, 2014 at 04:55 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 2. Solar wind speed at SOHO ranged between 371 and 499 km/s.

Solar flux at 20h UTC on 2.8 GHz was 154.7 (increasing 5.9 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 155.3. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 11111112 (planetary), 11113312 (Boulder).

The background x-ray flux is at the class B9 level.

At the time of counting spots (see image time), spots were observed in 12 active regions in 2K resolution (SN: 279) and 11 active regions in 1K resolution (SN: 187) SDO images on the visible solar disk.

Region 12021 [S13W15] was quiet and stable, the region has the potential to produce an M class flare.
Region 12022 [N17W01] decayed slowly and quietly.
Region 12024 [N17W31] was quiet and stable.
Region 12026 [S11E40] developed slowly and still has a magnetic delta structure in the central spot section. C and M class flares are possible.
Region 12027 [N12E43] was  mostly unchanged. C5+ flare: major M6.5/2B long duration event peaking at 14:05 UTC. This flare was associated with a full halo CME. Activity in nearby AR 12030 may have triggered the flare which was also associated with a large filament eruption to the north of the region.
Region 12028 [S08E51] decayed slowly and quietly.
Region 12029 [N17E28] developed slowly and quietly.
New region 12030 [N10E57] rotated into view on April 1 and was numbered the next day by SWPC. The region is unstable and could produce a minor M class event.  C5+ flare: C5.3 at 18:18 UTC.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3288 [N05E32] was quiet and stable.
New region S3295 [S07E08] emerged with penumbra spots.
New region S3296 [S01E11] emerged with penumbra spots.
New region S3297 [N06W15] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

March 31: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
April 1: A filament eruption from approx. 14:30 to 17h UTC in just east of the central meridian mostly in the southeast quadrant and extending into the northeast quadrant was the likely source of a full halo CME observed a little later in LASCO imagery.
April 2: A large and fast asymmetrical full halo CME was observed after the M6.5 event in AR 12027. The CME could reach Earth on April 4.

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 trans equatorial coronal hole (CH609) was in an Earth facing position on March 28-29.

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 poor.

Forecast

The geomagnetic field is expected to be quiet on April 3. The slow CME observed after a filament eruption on April 1 could arrive during on April 4 and cause unsettled and active intervals. The CME observed on April 2 is significantly larger and faster and could overtake the first CME and reach Earth on April 4. Active and minor storm intervals are possible.

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
12018	2014.03.24				N04W89						plage location: N05W82
12020	2014.03.24 2014.03.27				S13W53
S3264	2014.03.26				N08W39						plage
S3267	2014.03.26				S22W33						plage
12022	2014.03.27 2014.03.28	1	10	7	N17W03	0020	HSX	CRO	images/AR_12022_20140402_2345.png		area: 0040
12025	2014.03.27 2014.03.30				S24W61						location: S20W56
12021	2014.03.28	12	22	9	S13W17	0330	DKI	DKO			area: 0640 location: S13W15
12024	2014.03.28 2014.03.29		4		N17W37	0008		AXX			location: N17W31
S3276	2014.03.28				S12W23						plage
S3277	2014.03.28				S27W22					images/AR_S3277_20140401_2345.png
S3278	2014.03.28				S17W45						plage
S3280	2014.03.28				N09W39						plage
12026	2014.03.30	24	68	26	S11E38	0210	EAI	EKC			beta-gamma-delta location: S11E40 area: 0430
12027	2014.03.30 2014.03.31	1	7	5	N12E42	0100	HAX	CAO			area: 0240
S3285	2014.03.30				S10W49						plage
S3288	2014.03.31		6	2	N05E32	0017		BXO
12028	2014.03.31 2014.04.01	3	5	4	S08E51	0030	DAO	DRO
S3290	2014.03.31				S20E16						plage
12029	2014.04.01	8	15	10	N17E28	0030	CAO	DAI			area: 0120
12030	2014.04.01	7	17	10	N10E57	0020	CRO	DRI			area: 0080
S3294	2014.04.01				S05W43						plage
S3295	2014.04.02		2	2	S07E08	0007		BXO
S3296	2014.04.02		2	1	S01E11	0006		BXO
S3297	2014.04.02		1	1	N06W15	0004		AXX
Total spot count:		56	159	77
Sunspot number:		126	279	187	(total spot count + 10 * number of spotted regions)
Weighted SN:		92	198	116	(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):		76	98	103	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.