Solar Terrestrial Activity Report

Last major update issued on August 28, 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 August 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 2, 2011)]

[POES auroral activity level since October 2009 - updated August 25, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2111 [June-July 2011]  - 2112 [July 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on August 27. Solar wind speed ranged between 336 and 424 km/s. After 18h UTC solar wind speed and temperature increased as the leading part of the high speed stream associated with CH473 gradually became the dominant solar wind source.

Solar flux measured at 20h UTC on 2.8 GHz was 103.8 (decreasing 14.8 over the last solar rotation). The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.9). Three hour interval K indices: 20002222 (planetary), 20112211 (Boulder).

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

At midnight UTC the visible solar disk had 7 spotted regions (in 2K resolution SDO images).

Region 11271 decayed further as it rotated to the northwest limb.
Region 11275 decayed slowly and was quiet.
Region 11277 was quiet and stable.
Region 11279 was quiet and stable.
Region 11280 was quiet and stable.

Spotted regions not numbered by NOAA/SWPC:
[S1182] emerged in the southeast quadrant on August 25. Location at midnight: S19W17
[S1184] rotated partly into view at the southeast limb on August 27. Location at midnight: S21E83

Coronal mass ejections (CMEs)

August 25-27: No obviously Earth directed CMEs were observed in LASCO or 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 coronal hole (CH473) in the northern hemisphere was in an Earth facing position on August 24-25.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using the new method, the extent and intensity of both holes are consistent with other data sources.

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 to unsettled with a chance of active intervals on August 28 due to effects from CH473. On August 29-31 mostly quiet conditions are likely.

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
11271 2011.08.14
2011.08.15
4 1 N16W82 0060 CSO HSX

 

11272 2011.08.15
2011.08.16
    S21W76          

plage

11274 2011.08.19
2011.08.20
    N17W23         location: N18W18
11275 2011.08.20
2011.08.21
2 6 N07W08 0030 CSO BXO location: N07W05
11278 2011.08.23
2011.08.25
    N16W67         plage
11276 2011.08.23     N20W07           region should be deleted, spot was the trailing spot of region 11274
11277 2011.08.24
2011.08.25
1 5 N17E38 0080 HSX HSX location: N17E40
11280 2011.08.24 3 8 N17E10 0020 CRO DRO  
11279 2011.08.25 3 5 N13E47 0120 HSX CSO location: N13E48
S1182 2011.08.25   2 S18W05 0000   AXX  
S1183 2011.08.26     N23W71         plage
S1184 2011.08.27   4 S21E83 0080   CAO    
Total spot count: 13 31  
Sunspot number: 63 101  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 36 54  (Sum of total spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 38 33  k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO

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
2010.05 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 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 31.0 (+2.2) 4.32 / 5.51
2011.02 94.6 29.4 (33.6 predicted, +2.6) 5.41 / 6.44
2011.03 115.0 56.2 (36.6 predicted, +3.0) 7.79 / 8.18
2011.04 112.6 54.4 (39.4 predicted, +2.8) 9.71 / 8.83
2011.05 95.8 41.6 (42.7 predicted, +3.3) 9.18 / 8.94
2011.06 95.8 37.0 (46.5 predicted, +3.8) 8.96
2011.07 94.2 43.9 (50.6 predicted, +4.1) 9.14
2011.08 101.5 (1) 54.7 (2A) / 62.8 (2B) (54.8 predicted, +4.2) (8.58)

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.