Solar Terrestrial Activity Report

Last major update issued on May 23, 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 20, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2108 [March-April 2011] - 2109 [April-May 2011] NEW

Recent activity

The geomagnetic field was quiet on May 22. Solar wind speed ranged between 372 and 494 km/s under the influence of a weak coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 84.5 (decreasing 27.6 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: 22001111 (planetary), 22112101 (Boulder).

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

At midnight UTC the visible solar disk had 8 spotted regions.

Region 11216 was quiet and stable.
Region 11218 was quiet and stable.
Region 11219 was quiet and stable.
New region 11220 emerged in the northwest quadrant on May 21 and was numbered the next day by NOAA/SWPC.

Spotted regions not numbered by NOAA/SWPC:
[S1010] emerged in the southeast quadrant on May 15. Location at midnight: S18W31
[S1018] emerged in the northeast quadrant on May 19, became spotless on May 21 and reemerged on May 22. Location at midnight: N17W03
[S1020] emerged in the southwest quadrant on May 20. Location at midnight: S33W39
[S1023] emerged in the southwest quadrant on May 22. Location at midnight: S18W57

A filament erupted near 02h UTC on May 23 in the northeast quadrant. A CME may have been associated with this event.

Coronal mass ejections (CMEs)

May 20-22: 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 recurrent trans equatorial coronal hole (CH450) will likely rotate into an Earth facing position on May 24-25.

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 to fair.

Forecast

The geomagnetic field is expected to be quiet on May 23-25.

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
11214 2011.05.13
2011.05.14
1   S23W94 0030 HSX     rotated out of view
11216 2011.05.15
2011.05.16
1 4 S15W11 0080 HSX CSO location: S17W10
S1010 2011.05.15   3 S18W31 0000   AXX  
S1011 2011.05.15     N08W47           plage
11218 2011.05.17
2011.05.18
1 4 S16E14 0010 AXX BXO

location: S17E16

S1018 2011.05.19   4 N17W03 0000   BXO    
S1019 2011.05.20     N15E19           plage
S1020 2011.05.20   2 S33W39 0000   AXX  
11219 2011.05.21   1 N15E57 0000   AXX location: N13E53
S1021 2011.05.21     S13E70         plage
11220 2011.05.21
2011.05.22
4 9 N14W65 0010 BXO BXO formerly region S1022

location: N12W64

S1023 2011.05.22   5 S18W57 0010   BXO    
Total spot count: 7 32  
Sunspot number: 47 112  

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 96.2 (1) 41.9 (2A) / 59.1 (2B) (44.1 predicted, +3.3) (7.18)

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.