Solar Terrestrial Activity Report

Last major update issued on May 9, 2011 at 04:30 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 8. Solar wind speed ranged between 271 and 329 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 102.2 (decreasing 3.6 over the last solar rotation). The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.0). Three hour interval K indices: 10001011 (planetary), 10010111 (Boulder).

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

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

Region 11203 was quiet and stable.
Region 11204 decayed and lost all penumbra on the trailing spots.
Region 11205 was quiet and stable.
Region 11207 was quiet and stable.
New region 11208 emerged in the northeast quadrant on May 7 and was numbered the next day by NOAA/SWPC. The region developed on May8 and may be capable of C class flaring.
New region 11209 emerged in the northeast quadrant on May 7 and was assigned an SWPC number the following day.

Spotted regions not numbered by NOAA/SWPC:
[S992] reemerged on May 8. Location at midnight: S13W08
[S993] emerged in the northeast quadrant on May 5. Development was slow on May 8 with several new tiny spots observed. Location at midnight: N19E20
[S998] emerged with tiny spots in the northeast quadrant on May 8. Location at midnight: N15E43

Coronal mass ejections (CMEs)

May 6-8: 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. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on May 9-11.

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 N18W55 0100 HSX HSX location: N18W53
11204 2011.04.30
2011.05.02
9 16 N17W41 0090 DAO CAO

location: N17W43

11205 2011.04.30
2011.05.02
  3 N14W33 0000   BXO location: N17W23
S986 2011.05.01     S23W56         plage
S990 2011.05.03     N29W18        

plage

11207 2011.05.03
2011.05.05
  4 N24W02 0000   AXX

location: N22W10

S992 2011.05.04   5 S13W08 0010   CRO    
S993 2011.05.05   19 N19E20 0030   BXO  
S994 2011.05.06     S23W32           plage
11208 2011.05.07
2011.05.08
6 11 N13E49 0030 CRO DAO formerly region S995

area: 0070

11209 2011.05.07
2011.05.08
5 9 N35E08 0010 BXO BXO formerly region S996
S997 2011.05.07     N12W03         plage
S998 2011.05.08   2 N15E43 0000   AXX    
Total spot count: 21 70  
Sunspot number: 61 160  

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
2011.05 105.1 (1) 16.8 (2A) / 65.3 (2B) (44.1 predicted, +3.3) (9.44)

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.