Solar Terrestrial Activity Report

Last major update issued on February 24, 2012 at 04:55 UTC. Minor update posted at 05:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update February 2, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update February 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update February 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update February 5, 2012)]

[POES auroral activity level since October 2009 - updated February 24, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on February 23. Solar wind speed ranged between 366 and 490 km/s. After 18h UTC a low speed stream, likely from CH502, became the dominant solar wind source.

Solar flux measured at 20h UTC on 2.8 GHz was 103.3 (decreasing 25.3 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: 10110102 (planetary), 00221212 (Boulder).

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

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11420 [N12W70] decayed slowly and quietly.
Region 11421 [N15W05] decayed slightly and was quiet.
Region 11422 [N15W50] decayed slowly and quietly. There's a weak magnetic delta structure at the southeastern edge of the large penumbra.
New region 11423 [N16E70] rotated into view at the northeast limb on February 22 and got an SWPC number the next day.

Spotted regions not reported by NOAA/SWPC:
[S1489] emerged in the southeast quadrant on February 22 and developed slowly on Feb.23. Location at midnight: S15E23
[S1490] emerged in the southeast quadrant on February 22. Location at midnight: S17E33
[S1493] emerged in the northeast quadrant on February 23. Location at midnight: N22E53

Minor update added at 05:25 UTC on Feb.24: The filament eruption in the northeast quadrant became a spectacular view over the last hours. A new coronal hole formed between AR11421 and the southern part of the filament. Only STEREO-B images currently covers the last hours and shows a significant CME emerging. This CME will highly likely become geoeffective and could reach Earth on Feb.26 or early on Feb.27.

Coronal mass ejections (CMEs)

February 21-22: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
February 23: A filament eruption near the northwest limb (and spotless AR 11419) starting at 07:46 UTC was the source of a partial halo CME. This CME is not expected to become geoeffective. A very long filament in the northeast quadrant (starting to the east of AR 11421, then curving southwards before continuing northeastwards to and beyond the northeast limb) began erupting in the evening. The eruption was still in progress early on Feb.24, however, only a minor CME has been observed so far.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent coronal hole in the southern hemisphere (CH502) was in an Earth facing position on February 20-21. A recurrent coronal hole in the northern hemisphere willl likely rotate into an Earth facing position on February 26-27.

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 24 due to effects from CH502 and quiet on February 25. The CME observed early on Feb.24 could reach Earth on Feb.26 or 27 and cause unsettled to major storm conditions. The coronal hole formed by the filament eruption could lengthen the disturbance as a high speed stream is likely to be trailing the CME.

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 magnetic polarity overlay		Comment
		SWPC	STAR SDO				SWPC	STAR	Current	Previous
			2K	1K
11419	2012.02.12				N27W72						plage
11420	2012.02.12	1	1	1	N11W71	0030	HRX	HRX			location: N12W70
11421	2012.02.17 2012.02.18	1	8	2	N14W06	0000	AXX	BXO
S1483	2012.02.17				N42W47						plage
11422	2012.02.18 2012.02.19	9	14	8	N15W52	0130	CAO	DHI			area: 0320 location: N15W50
S1486	2012.02.18				N07W37						plage
S1487	2012.02.19				S13W44						plage
S1488	2012.02.19				S21W24						plage
S1489	2012.02.22		7	3	S15E23	0010		BXO
S1490	2012.02.22		2	1	S17E33	0000		AXX
11423	2012.02.22 2012.02.23	1	1	1	N18E70	0120	HSX	HSX			location: N16E70 area: 0210
S1492	2012.02.22				N15W45						plage
S1493	2012.02.23		1		N22E53	0000		AXX
Total spot count:		12	34	16
Sunspot number:		52	104	76	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		25	52	34	(Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number):		31	47		k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1, 2011) for STAR SDO 2K

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.