Solar Terrestrial Activity Report

Last major update issued on March 24, 2011 at 05:35 UTC. Minor update posted at 17:10 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 23, 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 23. Solar wind speed ranged between 404-483 km/s under the influence of a coronal hole stream from CH441/442.

Solar flux measured at 20h UTC on 2.8 GHz was 104.6 (increasing 15.7 over the last solar rotation). The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.0). Three hour interval K indices: 32322322 (planetary), 32432322 (Boulder).

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

At midnight UTC the visible solar disk had 4 spotted regions.

Region 11175 decayed quickly and will rotate out of view at the northwest limb today.
Region 11176 did not display any significant changes. M flares are possible. Flares: M1.4 at 02:17 and C1.1 at 17:10 UTC.
New region 11177 rotated into view at the northeast limb on March 21 and was noticed by NOAA/SWPC two days later.

Spotted regions not numbered by NOAA/SWPC:
[S912] This region emerged in the northeast quadrant on March 21. Location at midnight: N10W18

Minor update added at 17:10 UTC on March 24: Region 11176 produced an impulsive M1.0 flare at 12:07 UTC. The region is slowly becoming more complicated. Opposite polarity spots in the southern part of the region are closely separated. New region S916 emerged near the southeast limb early today (current location: S16E74), new region S917 is rotating into view at the southeast limb (current location: S25E85) and new region S918 is coming into view at the northeast limb (current location: N23E86). Region S915 has reemerged with a tiny spot while regions S912 and 11177 are both developing slowly. The newest high resolution STAR CHARMAP.

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

No obvious coronal holes are currently in or near Earth facing positions.

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

Forecast

The geomagnetic field is expected to quiet to unsettled on March 24 due to effects from CH441 and CH442. Quiet conditions are likely on March 25-26.

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
11173	2011.03.15 2011.03.16			S29W53						plage
S908	2011.03.17			N29W51						plage
11175	2011.03.17 2011.03.18	3	3	N11W76	0080	CSO	BXO			area: 0010
S911	2011.03.18			S22W29						plage
11176	2011.03.21	12	18	S15E58	0490	EKO	EKO			beta-gamma
S912	2011.03.21		3	N10W18	0000		BXO
11177	2011.03.21 2011.03.23	1	4	N21E51	0010	AXX	BXO			formerly region S914
S915	2011.03.22			S15W10						plage
Total spot count:		16	28
Sunspot number:		46	68

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.