Solar Terrestrial Activity Report

Last major update issued on February 11, 2011 at 04:30 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 10. Solar wind speed ranged between 339 and 393 km/s under the influence of a weak coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 91.4 (increasing 12.1 over the last solar rotation). The planetary A index  was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.0). Three hour interval K indices: 00211001 (planetary), 01321111 (Boulder).

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

At midnight UTC the visible solar disk had 5 spotted regions.

(Region 11153 continued to produce flares from behind the northwest limb. There is still a slight chance of an M class event. Flares: C1.9 at 06:40, C2.0 at 06:58, C4.7 at 12:34 and C2.6 at 13:52 UTC.)
Region 11156 developed slowly and has rudimentary penumbra on both polarities with many intermediate spots.
Region 11157 decayed and was quiet.

Spotted regions not numbered by NOAA/SWPC:
[S873] This region emerged in the southeast quadrant on February 10 and is developing moderately quickly early on February 11. Location at midnight: S19E38
[S874] A new region emerged in the northeast quadrant on February 10. Location at midnight: N20E42
[S875] This region emerged in the northeast quadrant to the east of region S874. Location at midnight: N21E54

Coronal mass ejections (CMEs)

February 8-10: 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 11-13.

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 polarity overlay
Comment
SWPC STAR SWPC STAR Current Previous
11154 2011.02.08     N08W77           plage
11155 2011.02.08
2011.02.07
    N17E00           2 threshold spots observed
11156 2011.02.08 11 19 S14E09 0020 DRO ERI location: S20E09

area: 0040

11157 2011.02.08 7 5 N22E08 0020 CRO CRO location: N20E09
S873 2011.02.10   4 S19E38 0000   BXO    
S874 2011.02.10   3 N20E42 0000   BXO    
S875 2011.02.10   1 N20E42 0010   AXX    
Total spot count: 18 32  
Sunspot number: 38 82  

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 83.5 (1) 13.5 (2A) / 37.9 (2B) (25.5 predicted, +1.7) (7.40)

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.