Solar Terrestrial Activity Report

Last major update issued on May 31, 2013 at 05:10 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, 2013)] [Cycle 24 progress (last update April 7, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 6, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated May 12, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was very quiet on May 30. Solar wind speed at SOHO ranged between 327 and 452 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 104.1 (decreasing 43.8 over the last solar rotation). The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.9). Three hour interval K indices: 00000100 (planetary), 10011211 (Boulder).

The background x-ray flux was at the class B2 level.

At midnight UTC the visible solar disk had 9 spotted active regions (in 2K resolution SDO images).

Region 11755 [N12W54] decayed further and could soon become spotless.
Region 11756 [S18W73] decayed slowly and quietly.
Region 11757 [S08E02] was quiet and stable.
Region 11758 [S19E25] gained a few spots and was quiet.
Region 11760 [N10E52] developed slowly and quietly.
Region 11761 [S19E39] was quiet and stable.

Spotted regions not numbered by SWPC:
S2446 [S25E03] gained a trailing spot.
New region S2453 [N16W03] emerged with penumbra spots.
New region S2454 [N12W31] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

May 28-30: 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 recurrent trans equatorial coronal hole (CH571) was in an Earth facing position on May 29-30.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and 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 on May 31. Quiet to active conditions are possible on June 1-2 due to effects from CH571.

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: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% 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	STAR SDO				SWPC	STAR	Current	Previous
			2K	1K
11754	2013.05.18 2013.05.20				S19W83						plage
11753	2013.05.19 2013.05.20				N05W79						plage
11756	2013.05.20 2013.05.21	2	2	2	S18W73	0070	HSX	HAX
11755	2013.05.20 2013.05.21	1	3	1	N12W59	0010	AXX	BXO
11757	2013.05.24 2013.05.25	1	4	1	S08W00	0030	HSX	CSO			area: 0090
11758	2013.05.26	2	13	3	S22E21	0010	AXX	BXO
11759	2013.05.26 2013.05.27				S07E22						plage
S2444	2013.05.26				N15W34						plage
S2446	2013.05.27		2		S25E03	0003		BXO
S2447	2013.05.27				N22W56						plage
11761	2013.05.28 2013.05.29	1	6	4	S18E37	0010	HSX	DRO			location: S19E39 area: 0025
S2449	2013.05.28				N12E21						plage
S2450	2013.05.28				S41W39						plage
11760	2013.05.29	4	10	4	N12E51	0010	BXO	DRO			area: 0035
S2451	2013.05.29				N18E48						plage
S2452	2013.05.29				N20E24						plage
S2453	2013.05.29		1	1	N16W03	0004		AXX
S2454	2013.05.30		2		N12W31	0004		AXX
Total spot count:		11	43	16
Sunspot number:		71	133	86	(total spot count + 10 * number of spotted regions)
Weighted SN:		26	59	32	(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):		43	47	47	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K

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 SIDC 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 Potsdam WDC ap indices.

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