Solar Terrestrial Activity Report

Last major update issued on February 22, 2011 at 04:35 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 21. Solar wind speed ranged between 331 and 429 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 96.7 (increasing 16.2 over the last solar rotation). The planetary A index  was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.8). Three hour interval K indices: 22122222 (planetary), 22122222 (Boulder).

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

At midnight UTC the visible solar disk had 3 spotted regions.

Region 11160 (SWPC duplicate number is 11161) decayed significantly and was mostly quiet. Flare: C1.4 at 18:35 UTC.
Region 11162 decayed further with only tiny spots remaining in the trailing spot section.

Region 11158 produced several C flares from behind the southwest limb: C4.6 at 02:24, C1.8 at 03:15, C1.5 at 04:10, C4.1 at 05:06, C4.3 at 06:10, C2.7 at 09:06, C1.8 at 10:04, C7.8 at 10:12, C1.5 at 15:54 UTC.

Coronal mass ejections (CMEs)

February 19-21: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

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. An extended area with weak corona was Earth facing on February 20-21.

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

Forecast

The geomagnetic field is expected to be mostly quiet on February 22-24. There's a chance of a few unsettled intervals on February 25.

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
S876 2011.02.11     S17W59           plage
11160 2011.02.12 25 29 N11W42 0220 EKC ESI

SWPC: 11161

S878 2011.02.13     N21W58           plage
11162 2011.02.18
2011.02.17
15 11 N17W46 0120 DAO CSO  
S883 2011.02.18     S20W63           plage
S884 2011.02.21   1 N20W13 0000   AXX   plage
Total spot count: 40 41  
Sunspot number: 60 71  

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 95.9 (1) 43.7 (2A) / 58.3 (2B) (25.5 predicted, +1.7) (6.33)

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.