Solar Terrestrial Activity Report

Last major update issued on March 24, 2013 at 05:40 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 active on March 23. Solar wind speed at SOHO ranged between 344 and 404 km/s. A weak disturbance was observed arriving at ACE near 17:30 UTC and caused unsettled to active conditions for the remainder of the day. Early on March 24 the disturbance has subsided.

Solar flux measured at 20h UTC on 2.8 GHz was 98.2 (increasing 2.8 over the last solar rotation). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.8). Three hour interval K indices: 21112234 (planetary), 21223334 (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 11700 [S13W27] was quiet and stable.
Region 11702 [N08W51] developed slowly and quietly.
Region 11703 [S24W73] decayed slowly and quietly.
New region 11704 [N15E72] rotated into view.

Spotted regions not numbered by SWPC:
S2310 [S22E27] was quiet and stable.
S2311 [S10W08] was quiet and stable.
New region S2312 [N30W12] emerged with a single spot.

Coronal mass ejections (CMEs)

March 21-23: 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) will likely rotate into an Earth facing position on March 25-26. A recurrent northern hemisphere coronal hole (CH563) could rotate into an Earth facing position on March 27.

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 poor.

Forecast

The geomagnetic field is expected to be quiet on March 24-27. A high speed stream from CH562 could cause quiet to active conditions on March 28-29.

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
11695	2013.03.10 2013.03.11	1			N09W90	0060	HSX				rotated out of view
S2292	2013.03.15				S27W52						plage
11700	2013.03.15 2013.03.17		6		S13W29	0010		AXX			location: S13W27
S2299	2013.03.15				N18W24						plage
S2301	2013.03.17				S13W40						plage
S2305	2013.03.18				N07W59						plage
11703	2013.03.19 2013.03.22	7	10	6	S25W72	0080	DAO	DRI			area: 0070
11702	2013.03.20 2013.03.21	7	12	9	N08W51	0050	CAO	DAI			area: 0090
S2309	2013.03.21				N00W23						plage
S2310	2013.03.22		4	1	S22E27	0007		BXO
S2311	2013.03.22		1		S10W08	0002		AXX
11704	2013.03.23	1	1	1	N15E74	0060	HSX	HAX
S2312	2013.03.23		1		N30W12	0003		AXX
Total spot count:		16	35	17
Sunspot number:		56	105	57	(total spot count + 10 * number of spotted regions)
Weighted SN:		36	48	30	(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):		34	37	31	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.