Solar Terrestrial Activity Report

Last major update issued on February 27, 2011 at 05:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update February 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update February 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update February 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update February 1, 2011)]

[POES auroral activity level charts since October 2009 - updated February 26, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2105 [Dec-Jan.2011] - 2106 [Jan.-Feb.2011] NEW

The geomagnetic field was quiet on February 26. Solar wind speed ranged between 297 and 326 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 90.2 (increasing 8.6 over the last solar rotation). The planetary A index  was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.5). Three hour interval K indices: 01111111 (planetary), 01221222 (Boulder).

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

At midnight UTC the visible solar disk had 3 spotted regions.

Region 11163 decayed slowly and was mostly quiet.
Region 11164 added some small spots. The main penumbra is complex and has a magnetic delta configuration. M flares are possible. Flare: C1.3 at 08:13 UTC.
New region 11165 emerged in the southeast quadrant on February 25 and was numbered the next day by NOAA/SWPC.

February 24-26: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

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 coronal hole (CH436) in the northern hemisphere was in an Earth facing location on February 23, CH436 has since then closed A recurrent trans equatorial coronal hole (CH437) was in an Earth facing position on February 25-26 and appears to be decaying. Another part (CH438) of what was a single coronal hole during the previous rotation, will likely be Earth facing on February 27 -  March 1. CH438 is a large trans equatorial coronal hole.

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

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.

The geomagnetic field is expected to be quiet on February 27-28. Quiet to unsettled is possible on March 1 due to effects from CH437 and quiet to minor storm on March 2-3 due to a high speed stream from CH438.

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
S885	2011.02.22			S14W36						plage
11163	2011.02.24	9	8	N18E46	0110	DAI	CRO			area: 0020
11164	2011.02.25	7	20	N28E60	0200	DAO	DAI			beta-gamma-delta area: 0120
S886	2011.02.25			N12W45						plage
11165	2011.02.26 2011.02.25	3	4	S22E43	0020	BXO	CRO			formerly region S887
Total spot count:		19	32
Sunspot number:		49	62

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.