Solar Terrestrial Activity Report

Last major update issued on February 2, 2011 at 05:55 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 to unsettled on February 2. Solar wind speed ranged between 349 and 500 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 79.2 (decreasing 7.6 over the last solar rotation). The planetary A index  was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.3). Three hour interval K indices: 31112110 (planetary), 32122201 (Boulder).

The background x-ray flux is at the class A4 level.

At midnight UTC the visible solar disk had 4 spotted regions.

Region 11150 decayed further losing several spots and penumbra on both polarities.

Spotted regions not numbered by NOAA/SWPC:
[S868] This region emerged in the northeast quadrant on February 2 with a single tiny spot. Location at midnight: N36E10
[S869] A new region emerged in the northeast quadrant late on February 2. Only a single tiny spot was observed late in the day, spots in both polarities were visible early on February 3. Location at midnight: N16E09.
[S870] This region emerged early on February 2 in the southeast quadrant. Location at midnight: S18E22

Coronal mass ejections (CMEs)

January 31 - February 2: 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

A large recurrent coronal hole (CH435) in the northern hemisphere was in an Earth facing position on January 30-February 1.

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 to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 3-5 with a chance of active intervals due to effects from CH435.

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 Spot count Location at midnight Area Classification SDO / HMI continuum
image with polarity overlay
Comment
SWPC STAR SWPC STAR Current Previous
11150 2011.01.26 12 5 S20W02 0080 DSO BXO  
S867 2011.01.31     N26W13           plage
S868 2011.02.02   1 N36E10 0000   AXX    
S869 2011.02.02   1 N16E09 0000   AXX    
S870 2011.02.02   4 S18E22 0010   BXO    
Total spot count: 12 11  
Sunspot number: 22 51  

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
2010.12 84.2 14.5 (22.2 predicted, +1.5) 3.41
2011.01 83.6 19.1 (23.8 predicted, +1.6) 4.32
2011.02 79.6 (1) 1.6 (2A) / 22.0 (2B) (25.5 predicted, +1.7) (6.81)

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 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.