Solar Terrestrial Activity Report

Last major update issued on May 10, 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 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 4, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2107 [Feb.-March 2011] - 2108 [March-April 2011]

Recent activity

The geomagnetic field was quiet on May 9. Solar wind speed ranged between 272 and 350 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 103.7 (decreasing 6.7 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.0). Three hour interval K indices: 11001111 (planetary), 11011311 (Boulder).

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

At midnight UTC the visible solar disk had 9 spotted regions.

Region 11203 was quiet and stable.
Region 11204 was quiet and stable.
Region 11205 was quiet and stable.
Region 11207 was quiet and stable.
Region 11208 developed slowly and was quiet.
Region 11209 was quiet and stable.
New region 11210 emerged in the northeast quadrant on May 5 and was numbered by NOAA/SWPC 4 days later. The region developed fairly quickly early in the day. Further C flares are possible. Flares: C1.4 at 05:16 and C1.5 at 17:41 UTC
New region 11211 was first observed with spots on May 4, became spotless, then reemerged on May 8 and got an SWPC number on May 9.

Spotted regions not numbered by NOAA/SWPC:
[S999] rotated into view at the southeast limb on May 9. Location at midnight: S14E78

A C5.4 flare was recorded at 20:59 UTC. Its source was a region currently at or just behind the northeast limb. The flare was associated with a fairly fast and large CME off the northeast limb.

Coronal mass ejections (CMEs)

May 7-9: 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

A coronal hole (CH448) in the southern hemisphere will likely rotate into an Earth facing position on May 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on May 10-13.

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 1 N18W68 0120 HSX HSX  
11204 2011.04.30
2011.05.02
3 6 N17W57 0100 CAO CSO

 

11205 2011.04.30
2011.05.02
  1 N14W47 0000   AXX location: N23W33
S990 2011.05.03     N29W31          

plage

11207 2011.05.03
2011.05.05
  7 N24W16 0000   BXO

location: N21W20

11211 2011.05.04
2011.05.09
2 6 S12W23 0010 BXO BXO formerly region S992
11210 2011.05.05
2011.05.09
13 26 N20E08 0030 DSI CSI formerly region S993

area: 0090

S994 2011.05.06     S23W45           plage
11208 2011.05.07
2011.05.08
9 9 N12E36 0100 DSO DSO  
11209 2011.05.07
2011.05.08
5 6 N35W05 0010 BXO BXO  
S997 2011.05.07     N12W03           plage
S998 2011.05.08     N15E30         plage
S999 2011.05.09   2 S14E78 0010   BXO    
Total spot count: 33 64  
Sunspot number: 93 154  

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
2011.05 105.0 (1) 19.8 (2A) / 68.3 (2B) (44.1 predicted, +3.3) (8.72)

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.