Solar Terrestrial Activity Report

Last major update issued on February 13, 2011 at 06:05 UTC. Minor update posted at 11:55 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]
Annotated geomagnetic activity charts - Carrington rotation 2104 [Nov-Dec.2010]- 2105 [Dec-Jan.2011] NEW

Recent activity

The geomagnetic field was quiet on February 12. Solar wind speed ranged between 348 and 417 km/s under the influence of a weak coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 95.6 (increasing 15.3 over the last solar rotation - and a new high for cycle 24). The planetary A index  was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 12211101 (planetary), 11212110 (Boulder).

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

At midnight UTC the visible solar disk had 6 spotted regions.

Region 11156 was mostly unchanged and quiet.
Region 11157 developed moderately quickly and could produce C flares.
Region 11158 developed slowly early in the day, then moderately quickly during the latter half of the day. Quick development has been observed early on February 13, and if this development continues, the region will soon become a complex, compact region with major flare potential.
Region 11159 developed slowly. Flare: C2.6 at 15:06 UTC.
New region 11160 rotated partly into view at the northeast limb. Only a single spot was observed at the end of the day, however, early on February 13 more spots are visible. The region displayed quite a bit of activity and appears to have polarity intermixing. C flares are possible and maybe even an M class flare.

Spotted regions not numbered by NOAA/SWPC:
[S877] This region emerged in the northwest quadrant on February 12. Location at midnight: N15W61

Minor update added at 11:55 UTC: Region 11158 continues to develop very quickly and is close to an EKC classification. A strong magnetic delta structure is forming in the center of the region. A major flare, even an X class flare, is possible. Compare the current active region image with the one furtrher below from just over 11 hours ago:

Coronal mass ejections (CMEs)

February 10-12: No obviously Earth directed CMEs were observed in LASCO or STEREO images.

Coronal holes

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

No significant coronal holes are currently in or near Earth facing positions.

The darkest areas on the solar disk are likely coronal holes.

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.

Forecast

The geomagnetic field is expected to be quiet on February 13-15.

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 polarity overlay
Comment
SWPC STAR SWPC STAR Current Previous
11155 2011.02.08
2011.02.07
    N17W26           plage
11156 2011.02.08 2 8 S21W22 0010 BXO BXO  
11157 2011.02.08 5 18 N18W18 0030 CRO CSI area: 0070
11158 2011.02.11
2011.02.10
12 35 S19E11 0040 DSI EAI area: 0130

beta-gamma

11159 2011.02.11
2011.02.10
4 7 N19E09 0010 BXO CRO  
S875 2011.02.10     N21E28           plage
S876 2011.02.11     S19E55         plage
11160 2011.02.12   1 N16E88 0010   AXX    
S877 2011.02.12   1 N15W61 0000   AXX    
Total spot count: 23 70  
Sunspot number: 63 130  

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
2009.11 73.6 4.1 7.6 (+0.5) 2.45 / 2.63
2009.12 76.7 10.8 8.3 (+0.7) 1.41 / 1.92
2010.01 81.1 13.2 9.3 (+1.0) 2.93 / 3.07
2010.02 84.7 18.8 10.6 (+1.3) 4.15 / 4.61
2010.03 83.4 15.4 12.3 (+1.7) 4.58 / 4.65
2010.04 75.9 8.0 14.0 (+1.7) 10.22 / 10.24
2010.05 73.8 8.7 15.5 (+1.5) 9.18 / 8.15
2010.06 72.5 13.6 16.4 (+0.9) 8.17 / 6.85
2010.07 79.8 16.1 16.8 (+0.4) 6.31 / 5.15
2010.08 79.2 19.6 (17.1 predicted, +0.3) 8.49 / 7.77
2010.09 81.1 25.2 (17.7 predicted, +0.6) 5.33 / 5.45
2010.10 81.6 23.5 (19.0 predicted, +1.3) 6.07 / 6.27
2010.11 82.5 21.6 (20.7 predicted, +1.7) 4.80 / 5.50
2010.12 84.2 14.5 (22.2 predicted, +1.5) 3.41 / 4.35
2011.01 83.6 19.1 (23.8 predicted, +1.6) 4.32
2011.02 85.1 (1) 17.7 (2A) / 41.3 (2B) (25.5 predicted, +1.7) (6.66)

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.