Solar Terrestrial Activity Report

Last major update issued on March 22, 2011 at 03:45 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, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2011)]

[POES auroral activity level charts since October 2009 - updated March 21, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011] NEW

Recent activity

The geomagnetic field was quiet to unsettled on March 21. Solar wind speed ranged between 283-344 km/s. A weak disturbance was observed beginning after 16h UTC at ACE, the source is uncertain (one possibility being a low speed stream from CH441). A huge backsided CME was observed early in the day, probably caused by an eruption in region 11169 (3 days behind the northwest limb). This event was likely the cause of a weak proton event still in progress. The only other possible source would be a large eruption in region 11176 on March 17.

Solar flux measured at 20h UTC on 2.8 GHz was 101.0 (increasing 10.1 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.5). Three hour interval K indices: 10100113 (planetary), 20111013 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight UTC the visible solar disk had 5 spotted regions.

Region 11173 was quiet and stable.
Region 11175 developed during the first half of the day with new flux emerging in the trailing spot section, late in the day the region appeared to be decaying.
New region 11176 rotated partly into view at the southeast limb as a compact region with mixed polarities. A major flare is possible. Flares: C2.6 at 11:47, C1.0 at 11:57 UTC.

Spotted regions not numbered by NOAA/SWPC:
[S912] This region emerged in the northeast quadrant on March 21. Location at midnight: N10E08
[S914] rotated into view at the northeast limb on March 21. Location at midnight: N20E81

A region 1-2 days behind the northeast limb was the source of a long duration C4.2 event peaking at 17:19 UTC. A CME was associated with this event.

Coronal mass ejections (CMEs)

March 19-21: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A small trans equatorial coronal hole (CH441) was in an Earth facing position on March 18-19. A coronal hole (CH442) in the northern hemisphere was Earth facing on March 19-20.

The darkest areas on the solar disk are likely coronal holes.

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 to fair.

Forecast

The geomagnetic field is expected to quiet to unsettled on March 22-24 due to effects from CH441 and CH442, occasional active intervals are possible.

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 polarity overlay		Comment
		SWPC	STAR SDO			SWPC	STAR	Current	Previous
11172	2011.03.10 2011.03.11			N13W66						location: N15W55
11173	2011.03.15 2011.03.16		6	S29W27	0000		BXO			location: S29W24
S908	2011.03.17			N29W25						plage
11175	2011.03.17 2011.03.18	13	17	N12W50	0140	DSO	DSI
S911	2011.03.18			S22W03						plage
11176	2011.03.21	1	4	S13E81	0180	HSX	DKC			beta-gamma area: 0500 location: S16E83
S912	2011.03.21		8	N10E08	0010		BXO
S914	2011.03.21		1	N20E81	0010		AXX
Total spot count:		14	36
Sunspot number:		34	86

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 preliminary daily SWPC ap indices. Values in red are based on the official NGDC 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.