Solar Terrestrial Activity Report

Last major update issued on February 26, 2011 at 06:45 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 very quiet on February 25. Solar wind speed ranged between 294 and 357 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 88.2 (increasing 6.8 over the last solar rotation). The planetary A index  was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.6). Three hour interval K indices: 00001111 (planetary), 00111111 (Boulder).

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

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

Region 11163 was mostly quiet and displayed no significant changes.
New region 11164 rotated into view at the northeast limb. The region is complex with a magnetic delta configuration in the southern penumbra. M flares are possible. Flares: C1.4 at 05:18, C1.6 at 05:44 and C1.1 at 17:29 UTC.

Spotted regions not numbered by NOAA/SWPC:
[S885] This region emerged in the southeast quadrant on February 22 and has since then had a few tiny spots. Location at midnight: S14W23
[S886] Spots emerged in this region in the northwest quadrant on February 25. Location at midnight: N12W32
[S887] This region emerged fairly quickly on February 25 in the southeast quadrant. Location at midnight: S22E57

February 22-24: 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) will be in an Earth facing position on February 25-26. Another part (CH438) of what was a single coronal hole during the previous rotation, will likely be Earth facing on February 27-28. 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 fair. Propagation on long distance northeast-southwest paths is poor.

The geomagnetic field is expected to be quiet to unsettled on February 26-28 due to weak coronal hole effects.

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
S884	2011.02.21			N20W65						plage
S885	2011.02.22		3	S14W23	0000		AXX
11163	2011.02.24	10	12	N17E60	0120	DAI	CRI			area: 0030
11164	2011.02.25	1	11	N28E76	0250	HKX	DAC			beta-delta area: 0110
S886	2011.02.25		2	N12W32	0000		BXO
S887	2011.02.25		6	S22E57	0010		CRO
Total spot count:		11	34
Sunspot number:		31	84

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.