Solar Terrestrial Activity Report

Last major update issued on April 1, 2013 at 04:25 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, 2013)] [Cycle 24 progress (last update March 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update Spril 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 on March 31. Solar wind speed at SOHO ranged between 437 and 523 km/s, weakly under the influence of a high speed stream from CH562.

Solar flux measured at 20h UTC on 2.8 GHz was 113.3 (decreasing 1.0 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.8). Three hour interval K indices: 10100112 (planetary), 11111321 (Boulder).

The background x-ray flux was at the class B3 level.

At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11704 [N15W33] was quiet and stable.
Region 11707 [S09W13] developed slowly and has weak polarity intermixing.
Region 11708 [N11E30] decayed slowly and quietly.
Region 11710 [S22E21] decayed in the leader spots section and was quiet.
Region 11711 [S18E64] was quiet. C and M class flares are possible.
New region 11712 [N02E37] emerged on March 30 and was numbered by SWPC the next day.

Spotted regions not numbered by SWPC:
S2314 [S20E08] reemerged with a penumbra spot.
New region S2327 [N14W66] emerged with a single spot.

Coronal mass ejections (CMEs)

March 29-31: 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) was in 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 poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on April 1 due to effects from CH562/563 and quiet on April 2-3.

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
11704	2013.03.23	2	15	6	N15W34	0070	HAX	CAO			area: 0110
11705	2013.03.24 2013.03.25				S12W66						plage
S2314	2013.03.25		1		S20E08	0002		AXX
11706	2013.03.26 2013.03.27				S07W52						plage
11709	2013.03.26 2013.03.29				S33W48						plage
11708	2013.03.27 2013.03.28	4	7	2	N11E30	0050	CSO	CSO
11707	2013.03.28	5	17	7	S11W12	0030	CAO	CRO			location: S09W13
11710	2013.03.28 2013.03.29	6	18	10	S22E20	0050	CAO	CRI
S2321	2013.03.28				S15E26						plage
S2322	2013.03.28				S14W23						plage
S2323	2013.03.28				S12W51						plage
11711	2013.03.29 2013.03.30	4	9	4	S17E62	0420	CKI	CKO			location: S18E64 area: 0600
11712	2013.03.30 2013.03.31	2	2	1	N01E38	0010	CRO	CRO
S2327	2013.03.31		1		N14W66	0003		AXX
Total spot count:		23	70	30
Sunspot number:		83	150	90	(total spot count + 10 * number of spotted regions)
Weighted SN:		58	99	59	(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):		50	53	50	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.