Solar Terrestrial Activity Report

Last major update issued on March 21, 2011 at 04:25 UTC. Minor update posted at 19:10 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 21, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011] NEW

Recent activity

The geomagnetic field was quiet on March 20. Solar wind speed ranged between 311-359 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 92.0 (decreasing 4.7 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.0). Three hour interval K indices: 01112202 (planetary), 12112212 (Boulder).

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

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

Region 11172 was quiet and decayed slowly.
Region 11173 decayed and could soon become spotless.
Region 11174 was quiet and stable.
Region 11175 did not display any significant changes and remained quiet.

Old region 11165 is currently at the southeast limb causing an increase in the background x-ray flux. C and maybe M flares are possible.

Minor update added at 15:35 UTC on March 21: Old region 11165 has rotated partly into view at the southeast limb with a large spot currently visible, see this high resolution image. The background x-ray flux is increasing. New region S912 has emerged in the northeast quadrant. Proton flux levels have increased today but have so far not reached event threshold.

Minor update added at 19:10 UTC: The region at the southeast limb is displaying more spots and appears to be very complex. A major flare is possible. Although it is quite unusual for a region at the east limb to cause proton events, this region could be capable of that. Otherwise region 11175 has developed quickly and is close to forming a magnetic delta structure in the trailing spot section. Both polarites have penumbra. Here's a close-up of the southeast limb:

Coronal mass ejections (CMEs)

March 18-20: 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to quiet to unsettled on March 21-24 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		3	N13W52	0000		BXO			location: N15W42
11173	2011.03.15 2011.03.16	5	4	S29W13	0020	BXO	BXO			area: 0000
S906	2011.03.16			N21W56						plage
11174	2011.03.16 2011.03.17	1	4	N23W76	0000	AXX	BXO
S908	2011.03.17			N29W12						plage
S909	2011.03.17			S22W62						plage
11175	2011.03.17 2011.03.18	11	23	N14W36	0130	CSI	CSI			location: N12W36
S911	2011.03.18			S22E10						plage
Total spot count:		17	34
Sunspot number:		47	74

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.