Solar Terrestrial Activity Report

Last major update issued on March 17, 2012 at 06:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update March 2, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2012)]

[POES auroral activity level since October 2009 - updated March 5, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Data source change from March 16: The source for planetary A and K indices has been changed from SWPC to WDC (Potsdam) to improve data quality. The change has been applied to old data in the above plot and will gradually be phased in where those data are otherwise used in STAR.

Recent activity

The geomagnetic field was active to minor storm on March 16. Solar wind speed at SOHO ranged between 547 and 801 km/s. Early in the day the dominant solar wind source was a CME, then gradually the high speed stream associated with CH507 became dominant.

Solar flux measured at 20h UTC on 2.8 GHz was 98.5 (decreasing 5.6 over the last solar rotation). The planetary A index was 33 (STAR Ap - based on the mean of three hour interval ap indices: 33.0). Three hour interval K indices: 54454544 (planetary), 53433433 (Boulder).

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

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

Region 11432 [N15W27] decayed further and could soon become spotless.
Region 11433 [N10W03] decayed significantly and was mostly quiet.
Region 11434 [S22W01] developed slowly and quietly.
Region 11435 [S25W23] was quiet and stable.
New region 11436 [S13E66] rotated into view at the southeast limb on March 15 and got an SWPC number the next day.

Spotted regions not reported by NOAA/SWPC:
[S1525] was split off from region 11432 on March 13. Decay was observed on March 16. Location at midnight: N13W24.
[S1530] emerged in the southeast quadrant on March 16. Location at midnight: S34E29

A filament eruption in the northwest quadrant was observed late in the day, the associated CME was seen off the northwest limb and the north pole.

Coronal mass ejections (CMEs)

March 15: A small CME was observed in STEREO imagery. This CME could reach Earth on March 18.
March 14 and 16: 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 large recurrent trans equatorial coronal hole (CH507) was in an Earth facing position on March 13-14.

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is very poor. Propagation on long distance northeast-southwest paths is fair to good.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on March 17 due to a high speed stream from CH507, quiet to unsettled is likely on March 18-19.

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 higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) 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
11432	2012.03.08 2012.03.09	20	3	1	N14W26	0080	ESI	BXO			location: N15W27 area: 0000 SWPC includes region S1525
11434	2012.03.10 2012.03.11	4	8	4	S22W14	0030	ESO	CSO			location: S22W11
11433	2012.03.10 2012.03.11	11	7	3	N13W04	0100	DSO	HSX			location: N10W03
11435	2012.03.11 2012.03.15	5	9	3	S25W24	0020	DSO	CRI
S1525	2012.03.13		5	2	N13W24	0030		DRO			inversion line added in images
S1526	2012.03.14				S24W03						plage
S1527	2012.03.14				N10W42						plage
11436	2012.03.15 2012.03.16	1	4	2	S12E62	0010	AXX	BXO			location: S13E66
S1529	2012.03.15				N16E29						plage
S1530	2012.03.16		2	1	S34E29	0010		BXO
Total spot count:		41	38	16
Sunspot number:		91	108	86	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		61	54	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):		55	38	47	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) 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) Month average to date.
3) Running average based on the quicklook 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.