Solar Terrestrial Activity Report

Last major update issued on February 25, 2011 at 04:20 UTC.

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[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
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[POES auroral activity level charts since October 2009]
Annotated geomagnetic activity charts - Carrington rotation 2104 [Nov-Dec.2010]- 2105 [Dec-Jan.2011] NEW

The geomagnetic field was very quiet on February 24. Solar wind speed ranged between 297 and 348 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 88.9 (increasing 8.2 over the last solar rotation). The planetary A index  was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.8). Three hour interval K indices: 01000111 (planetary), 01011210 (Boulder).

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

At midnight UTC the visible solar disk had 2 spotted regions.

New region 11163 rotated into view at the northeast limb. Flare: M3.5 at 07:35 (associated with a moderate type II radio sweep) and C1.8 at 13:53 UTC.

Spotted regions not numbered by NOAA/SWPC:
[S885] This region emerged in the southeast quadrant on February 22. Location at midnight: S16W06

Another region will likely rotate into view at the northeast limb today, further north than region 11163. A C2.7 flare at 19:38 UTC likely had its source in region 11160 behind the northwest limb.

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. A recurrent northern hemisphere coronal hole (CH437) will probably rotate into 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.

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 conditions on February 25-27 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
11160	2011.02.12	1		N11W87	0060	HAX				rotated out of view SWPC: 11161
S884	2011.02.21			N20W52						plage
S885	2011.02.22		2	S16W06	0000		AXX
11163	2011.02.24	2	7	N18E72	0200	CRO	BXO			area: 0020
Total spot count:		3	9
Sunspot number:		23	29

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.