Solar Terrestrial Activity Report

Last major update issued on May 18, 2011 at 04:45 UTC.

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

[POES auroral activity level charts since October 2009 - updated May 13, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2108 [March-April 2011] - 2109 [April-May 2011] NEW

Recent activity

The geomagnetic field was quiet to unsettled on May 17. Solar wind speed ranged between 539 and 600 km/s under the influence of a high speed stream from CH449.

Solar flux measured at 20h UTC on 2.8 GHz was 91.5 (decreasing 25.5 over the last solar rotation). The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.3). Three hour interval K indices: 22332333 (planetary), 12322232 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight UTC the visible solar disk had 7 spotted regions.

Region 11208 decayed quietly and will rotate over the northwest limb today
Region 11214 decayed slowly and quietly.
Region 11216 was quiet and stable.
New region 11217 emerged in the southeast quadrant on May 15 and was numbered by NOAA/SWPC 2 days later. The region decayed on May 17.

Spotted regions not numbered by NOAA/SWPC:
[S1008] emerged with tiny spots in an old plage area in the northeast quadrant on May 14. Location at midnight: N17W14
[S1010] emerged in the southeast quadrant on May 15. Location at midnight: S20E33
[S1016] rotated into view at the southeast limb on May 17. Location at midnight: S17E80

Coronal mass ejections (CMEs)

May 15-17: 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 poor. Propagation on long distance northeast-southwest paths is fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 18 due to a high speed stream from CH449. Quiet conditions are likely on May 19-21.

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
11208 2011.05.07
2011.05.08
2 8 N09W78 0010 BXO BXO  
12112 2011.05.09
2011.05.11
    S13W37           plage

location: S15W26

11215 2011.05.12
2011.05.14
    S23W70           plage
S1002 2011.05.12     S21W52           plage
S1004 2011.05.13     N06W35           plage
11214 2011.05.13
2011.05.14
12 15 S24W24 0060 CSO CSI location: S25W28
S1006 2011.05.13     S16W45           plage
S1008 2011.05.14   5 N17W14 0000   BXO  
11216 2011.05.15
2011.05.16
1 1 S15E54 0080 HSX HSX  
S1010 2011.05.15   1 S20E33 0000   AXX    
S1011 2011.05.15     N08E18         plage
S1012 2011.05.15     N29W34           plage
11217 2011.05.15
2011.05.17
2 9 S23W19 0010 BXO BXO formerly region S1013

location: S25W20

S1014 2011.05.16     S32E24         plage
S1015 2011.05.16     N12W36         plage
S1016 2011.05.17   3 S17E80 0010   BXO    
Total spot count: 17 42  
Sunspot number: 57 112  

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
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 16.7 (+0.3) 6.31 / 5.15
2010.08 79.2 19.6 17.4 (+0.7) 8.49 / 7.77
2010.09 81.1 25.2 19.6 (+2.2) 5.33 / 5.45
2010.10 81.6 23.5 23.2 (+3.6) 6.07 / 6.27
2010.11 82.5 21.5 (26.9 predicted, +3.7) 4.80 / 5.50
2010.12 84.2 14.4 (30.1 predicted, +3.2) 3.41 / 4.35
2011.01 83.6 19.1 (33.1 predicted, +3.0) 4.32 / 5.51
2011.02 94.6 29.4 (35.6 predicted, +2.5) 5.41 / 6.44
2011.03 115.0 56.2 (37.9 predicted, +2.3) 7.79
2011.04 112.6 54.4 (40.8 predicted, +2.9) 9.71
2011.05 99.4 (1) 34.7 (2A) / 63.2 (2B) (44.1 predicted, +3.3) (8.05)

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.