Solar Terrestrial Activity Report

Last major update issued on February 20, 2012 at 06:10 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 17, 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 to minor storm on February 19. Solar wind speed ranged between 338 and 476 km/s, gradually increasing all day under the influence of a high speed stream from CH501. Early on February 20 the disturbance has intensified to active to minor storming.

Solar flux measured at 20h UTC on 2.8 GHz was 105.3 (decreasing 39.0 over the last solar rotation). The planetary A index was 16 (STAR Ap - based on the mean of three hour interval ap indices: 15.8). Three hour interval K indices: 45211212 (planetary), 45322222 (Boulder).

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

At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11419 [N28W20] decayed quietly.
Region 11420 [N12W16] was quiet and stable.
Region 11421 [N18E47] was quiet and stable. The region was the source of a C4.1 flare at 05:09 on February 20.
New region 11422 [N16E03] emerged in the northeast quadrant on February 18 and got an SWPC number the next day. The region developed very quickly on Feb.19 and could produce M class flares.

Spotted regions not reported by NOAA/SWPC:
[S1480] reemerged on February 19. Location at midnight: N16W46
[S1484] emerged in the southwest quadrant near the central meridian on February 17. Location at midnight: S15W33
[S1487] emerged in the southeast quadrant on February 19. Location at midnight: S13E08
[S1488] emerged in the southeast quadrant on February 19. Location at midnight: S24E37

Coronal mass ejections (CMEs)

February 17-19: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

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 trans equatorial coronal hole (CH501) was in an Earth facing position on February 15-16. A recurrent coronal hole in the southern hemisphere (CH502) will likely rotate into an Earth facing position on February 20-21.

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

Forecast

The geomagnetic field is expected to be quiet to minor storm on February 20 due to effects from CH501. Quiet conditions are likely on February 21-22. A high speed stream from CH502 could arrive on February 23 and cause quiet to unsettled conditions.

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
11417	2012.02.09 2012.02.10				N18W66						plage
11418	2012.02.10 2012.02.12	3			S23W84	0020	CSO				spotless
11419	2012.02.12	3	4	3	N29W18	0020	CSO	CRO			location: N28W20
11420	2012.02.12	1	1	1	N11W16	0070	HSX	HSX
S1477	2012.02.13				S21W27						plage
S1478	2012.02.13				N25W54						plage
S1479	2012.02.13				N23W32						plage
S1480	2012.02.16		1		N16W46	0000		AXX
11421	2012.02.17 2012.02.18	2	3	1	N18E46	0010	AXX	AXX
S1482	2012.02.17				N14E52						plage
S1483	2012.02.17				N36W03						plage
S1484	2012.02.17		2	2	S15W33	0010		DRO
11422	2012.02.18 2012.02.19	10	16	8	N15E02	0060	DAI	DAI			area: 0380
S1486	2012.02.18				N07E15						plage
S1487	2012.02.19		1	1	S13E08	0000		AXX
S1488	2012.02.19		1		S24E37	0000		AXX
Total spot count:		19	29	16
Sunspot number:		69	109	76	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		39	45	32	(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):		41	49		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.