Solar Terrestrial Activity Report

Last major update issued on May 12, 2011 at 03:50 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 10, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2107 [Feb.-March 2011] - 2108 [March-April 2011]

Recent activity

The geomagnetic field was quiet to unsettled on May 11. Solar wind speed ranged between 341 and 414 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 94.1 (decreasing 24.6 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.5). Three hour interval K indices: 13101111 (planetary), 13111211 (Boulder).

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

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

Region 11204 decayed slowly and will rotate over the northwest limb today.
Region 11207 decayed slowly and quietly.
Region 11208 decayed slowly and was quiet.
Region 11210 decayed slowly and quietly.

Spotted regions not numbered by NOAA/SWPC:
[S1000] emerged in the southwest quadrant on May 11. Location at midnight: S20W42

Coronal mass ejections (CMEs)

May 9: A large, wide and fast partial halo CME was observed following a long duration C5.4 event at the northeast limb in the evening. There's a slight chance of a flank impact from this CME on May 13.
May 10: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
May 11: A filament eruption to the west of region 11207 early in the day was associated with a partial halo CME. Weak effects from this CME could reach Earth on May 14 or 15.

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 trans equatorial coronal hole (CH448) was in an Earth facing position on May 11-12.

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 May 12-14 becoming quiet to active on May 15-16 due to effects from CH448. There's a chance of unsettled intervals on May 13 and 14 due to possible flank CME effects.

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
11203 2011.04.28 1   N18W92 0060 HSX     rotated out of view
11204 2011.04.30
2011.05.02
1 1 N17W85 0050 HSX HRX

area: 0020

11205 2011.04.30
2011.05.02
    N14W75         plage
S990 2011.05.03     N29W57          

plage

11207 2011.05.03
2011.05.05
2 2 N21W51 0010 BXO AXX

 

11211 2011.05.04
2011.05.09
    S12W51           plage
11210 2011.05.05
2011.05.09
11 10 N19W21 0050 CSO CSO

area: 0030

11208 2011.05.07
2011.05.08
8 8 N12E08 0050 DSO DSO  
11209 2011.05.07
2011.05.08
    N35W33           plage
S997 2011.05.07     N12W29           plage
S998 2011.05.08     N15E04           plage
12112 2011.05.09
2011.05.11
1   S13E46 0010 AXX     formerly region S999

spotless

S1000 2011.05.11   3 S20W42 0000   BXO    
Total spot count: 24 24  
Sunspot number: 84 74  

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
2011.05 103.3 (1) 25.1 (2A) / 70.8 (2B) (44.1 predicted, +3.3) (8.35)

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.