Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 11, 2012 at 06:20 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 10, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2117 [November-December 2011] - 2118 [December 2011 - January 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on February 10. Solar wind speed ranged between 375 and 436 km/s, weakly under the influence of low speed stream from CH499.

Solar flux measured at 20h UTC on 2.8 GHz was 110.8 (decreasing 21.5 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 10111122 (planetary), 01212221 (Boulder).

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

At midnight UTC the visible solar disk had 5 spotted regions (in 2K resolution SDO images).

Region 11416 [S18E11] developed further forming large penumbrae in the leading and trailing spot sections. While the region currently only has weak polarity intermixing, there's potential for an M class flare.
New region 11417 [N17E61] rotated into view at the northeast limb on February 9 and was numbered by SWPC the next day.

Spotted regions not reported by NOAA/SWPC:
[S1461] reemerged with several spots on February 9 and decayed slowly on Feb.10. Location at midnight: N07W38
[S1469] emerged in the southeast quadrant on February 10. Location at midnight: S23E41
[S1470] emerged in the southwest quadrant on February 10. Location at midnight: S13W60

Coronal mass ejections (CMEs)

February 8-10: 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 recurrent trans equatorial coronal hole (CH500) was Earth facing on February 8-9.

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 poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 11-12 due to weak coronal hole effects. Quiet conditions are likely on February 13.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
     

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
11415 2012.02.02
2012.02.08
2     N08W84 0010 BXO     rotated out of view
S1461 2012.02.07   2   N07W38 0000   BXO  
11416 2012.02.08
2012.02.09
17 30 16 S17E10 0100 DSI EHI area: 0650
S1464 2012.02.08       S21E37           plage
11417 2012.02.09
2012.02.10
2 4 2 N18E59 0010 BXO CRO location: N17E61
S1466 2012.02.09       N16E37         plage
S1467 2012.02.09       N29W00         plage
S1468 2012.02.09       N11W27         plage
S1469 2012.02.10   2 1 S23E41 0010   BXO    
S1470 2012.02.10   1 1 S13W60 0000   AXX    
Total spot count: 21 39 20  
Sunspot number: 51 89 60  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 26 52 33  (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 40    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

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2010.11 82.5 21.5 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 31.0 (+2.2) 4.32 / 5.51
2011.02 94.6 29.4 33.4 (+2.4) 5.41 / 6.44
2011.03 115.0 56.2 36.9 (+3.5) 7.79 / 8.18
2011.04 112.6 54.4 41.8 (+4.9) 9.71 / 8.83
2011.05 95.8 41.6 47.6 (+5.8) 9.18 / 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.96 / 8.06
2011.07 94.2 43.9 57.2 (+4.0) 9.14 / 8.16
2011.08 101.7 50.6 (60.4 projected, +3.2) 8.16 / 7.26
2011.09 133.8 78.0 (63.1 projected, +2.7) 12.80 / 12.27
2011.10 137.3 88.0 (65.8 projected, +2.7) 7.52 / 8.28
2011.11 153.5 96.7 (69.1 projected, +3.3) 4.58 / 5.55
2011.12 141.3 73.0 (73.9 projected, +4.8) 3.32
2012.01 132.5 58.3 (79.3 projected, +5.4) 6.59
2012.02 107.3 (1) 15.2 (2A) / 44.1 (2B) (82.4 projected, +3.1) (7.54)

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.