Solar Terrestrial Activity Report

Last major update issued on March 17, 2011 at 05:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update March 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2011)]

[POES auroral activity level charts since October 2009 - updated March 11, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2105 [Dec-Jan.2011] - 2106 [Jan.-Feb.2011] NEW

Recent activity

The geomagnetic field was very quiet on March 16. Solar wind speed ranged between 305-367 km/s.

Solar flux measured at 17h UTC on 2.8 GHz was 93.8 (decreasing 17.1 over the last solar rotation. The measurements at both 20 and 23h UTC were enhanced by a long duration event). The planetary A index was 0 (STAR Ap - based on the mean of three hour interval ap indices: 0.5). Three hour interval K indices: 00000001 (planetary), 00000111 (Boulder).

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

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

Region 11169 decayed slowly and will rotate out of view at the northwest limb today. C flares are possible. Flares: C1.3at 08:47, C1.4 at 13:51 and a very long duration C3.7 event peaking at 20:34 UTC. The latter event was associated with a bright CME off the northwest limb.
Region 11171 was quiet and stable.
Region 11172 did not change significantly and was quiet.
New region 11173 emerged in the southeast quadrant on March 15 and was numbered the next day by NOAA/SWPC. The region developed slowly on March 16.

Spotted regions not numbered by NOAA/SWPC:
[S906] Tiny spots emerged to the northwest of region 11172 on March 16. Location a midnight: N21W04
[S907] This region emerged in the northwest quadrant on March 16. Location at midnight: N22W23

Coronal mass ejections (CMEs)

March 14-16: 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 obvious 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 fair to good. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on March 17-20.

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 SDO SWPC STAR Current Previous
11169 2011.03.05
2011.03.06
9 7 N17W75 0260 DHI CAO

location: N17W79

11171 2011.03.08   4 S19W43 0000   AXX  
S902 2011.03.10     N07W46         plage
11172 2011.03.10
2011.03.11
1 8 N11E02 0000 AXX BXO location: N13E09
S904 2011.03.13     S24W17           plage
11173 2011.03.15
2011.03.16
10 13 S28E29 0040 CAO CAO formerly region S905
S906 2011.03.16   3 N21W04 0000   AXX    
S907 2011.03.16   4 N22W23 0010   BXO    
Total spot count: 20 39  
Sunspot number: 50 99  

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
2009.12 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 17.4 (+0.6) 8.49 / 7.77
2010.09 81.1 25.2 (19.1 predicted, +1.7) 5.33 / 5.45
2010.10 81.6 23.5 (21.7 predicted, +2.6) 6.07 / 6.27
2010.11 82.5 21.6 (24.5 predicted, +2.8) 4.80 / 5.50
2010.12 84.2 14.5 (26.9 predicted, +2.4) 3.41 / 4.35
2011.01 83.6 19.1 (29.0 predicted, +2.1) 4.32
2011.02 94.6 29.4 (31.1 predicted, +2.1) 5.41
2011.03 124.0 (1) 46.3 (2A) / 89.8 (2B) (33.0 predicted, +1.9) (11.38)

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.