Solar Terrestrial Activity Report

Last major update issued on May 8, 2011 at 06:30 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 7. Solar wind speed ranged between 305 and 390 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 102.2 (decreasing 2.6 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 11102212 (planetary), 11112321 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight UTC the visible solar disk had 10 spotted regions.

Region 11203 decayed slowly and quietly.
Region 11204 was quiet. The region has mixed polarities and C flares are possible. The trailing spot section decayed and the region could be heading for a CAI or CAO classification.
Region 11205 decayed with only tiny spots in one polarity remaining.
Region 11207 decayed slowly and could soon become spotless.

Spotted regions not numbered by NOAA/SWPC:
[S986] reemerged with a tiny spot on May 7. Location at midnight: S23W43
[S990] reemerged on May 7. Location at midnight: N29W05
[S993] emerged in the northeast quadrant on May 5 and has slowly been adding tiny spots. Location at midnight: N12E35
[S995] emerged in the northeast quadrant on May 7. Location at midnight: N12E63
[S996] emerged in the northeast quadrant on May 7. Location at midnight: N33E19
[S997] emerged in the northeast quadrant on May 7. Location at midnight: N12E10

Coronal mass ejections (CMEs)

May 5-7: 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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on May 8-10.

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 4 3 N17W41 0070 HSX CSO location: N16W39
11206 2011.04.29
2011.05.03
    N22W74          

location: N22W67

plage

11204 2011.04.30
2011.05.02
14 21 N17W27 0130 DAO DAO

beta-gamma

11205 2011.04.30
2011.05.02
  4 N14W19 0000   AXX location: N20W05
S986 2011.05.01   1 S23W43 0000   AXX    
S990 2011.05.03   5 N29W05 0010   BXO  

 

11207 2011.05.03
2011.05.05
  6 N24E12 0000   BXO

location: N23E11

S992 2011.05.04     S17W09         plage
S993 2011.05.05   8 N12E35 0000   BXO  
S994 2011.05.06     S23W19         plage
S995 2011.05.07   6 N12E63 0030   BXO    
S996 2011.05.07   3 N33E19 0000   BXO    
S997 2011.05.07   2 N12E10 0000   AXX    
Total spot count: 18 59  
Sunspot number: 38 159  

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
2011.05 105.5 (1) 14.9 (2A) / 65.9 (2B) (44.1 predicted, +3.3) (10.5)

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.