Solar Terrestrial Activity Report

Last major update issued on March 28, 2013 at 07:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update March 1, 2013)] [Cycle 24 progress (last update March 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated March 24, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to minor storm on March 27. Solar wind speed at SOHO ranged between 363 and 514 km/s. A high speed coronal hole stream (probably associated with a short lived coronal hole that was open over the central meridian on March 24 following a filament eruption) began to influence the field early in the day.

Solar flux measured at 20h UTC on 2.8 GHz was 93.0 (decreasing 19.6 over the last solar rotation). The Potsdam WDC planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 17.3). Three hour interval K indices: 13333534 (planetary), 12323423 (Boulder).

The background x-ray flux was at the class B1 level.

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11704 [N15E19] was quiet and stable.
Region 11705 [S12W08] was quiet and stable.
New region 11706 [S06E04] emerged on March 26 and was numbered the next day by SWPC.

Spotted regions not numbered by SWPC:
S2316 [S34E06] decayed slowly and quietly.
New region S2317 [N10E83] rotated into view.
New region S2318 [N16W11] emerged with a penumbra spot.
New region S2319 [S55W39] emerged with a single spot at a high latitude.

Coronal mass ejections (CMEs)

March 25-27: 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 (CH562) was in an Earth facing position on March 25-27. A recurrent northern hemisphere coronal hole (CH563) will rotate into an Earth facing position on March 28.

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. Propagation on long distance northeast-southwest paths is fair.

Forecast

The geomagnetic field is expected to be quiet to active on March 28-31 due to effects from CH562/563.

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
11700	2013.03.15 2013.03.17				S13W85						plage
S2310	2013.03.22				S22W24						plage
11704	2013.03.23	2	9	1	N15E18	0080	HAX	CSO			area: 0120
11705	2013.03.24 2013.03.25	1	6	3	S12W11	0010	AXX	BXO			location: S12W08
S2314	2013.03.25				S18E54						plage
11706	2013.03.26 2013.03.27	2	8	3	S06E04	0010	BXO	DRO			area: 0040
S2316	2013.03.26		1		S34E06	0002		AXX
S2317	2013.03.27		1	1	N10E83	0060		HSX
S2318	2013.03.27		1		N16W11	0003		AXX
S2319	2013.03.27		1		S55W39	0003		AXX
Total spot count:		5	27	8
Sunspot number:		35	97	48	(total spot count + 10 * number of spotted regions)
Weighted SN:		10	40	21	(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):		21	34	26	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.