Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 28, 2012 at 05:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update August 6, 2012)] [Cycle 24 progress (last update August 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 6, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 6, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 5, 2012)]

[POES auroral activity level since October 2009 - updated August 5, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on August 27. Solar wind speed at SOHO ranged between 462 and 712 km/s under the weakening influence of a high speed stream associated with CH530.

Solar flux measured at 20h UTC on 2.8 GHz was 111.5 (decreasing 28.3 over the last solar rotation). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.1). Three hour interval K indices: 23210112 (planetary), 23222222 (Boulder).

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

At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).

Region 11552 [S14W36] lost most of the spots with only two tiny spots observed in the far western part of the leading polarity area.
Region 11553 [S22E08] decayed losing all trailing polarity spots.
Region 11554 [N16W28] decayed slowly and quietly.
Region 11555 [N08E44] added some spots while the trailing penumbra fragmented.
New region 11556 [S13W80] emerged in August 26 and was numbered by SWPC the next day as it rotated to the southwest limb.
New region 11557 [N17E38] emerged with 2 spots along a north-south axis.
New region 11558 [N17E78] rotated into view with a few small spots.

Spotted regions not numbered by NOAA/SWPC:
S1876 [N16E06] was quiet and stable.
New region S1881 [S19E35] emerged with a tiny spot.
New region S1882 [N21E65] emerged with a tiny spot.
New region S1883 [N13E72] rotated into view with two small spots.
New region S1884 [N15E56] emerged with a tiny spot.

Coronal mass ejections (CMEs)

August 25-27: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A small trans equatorial coronal hole (CH531) has developed over the last few days and was in an Earth facing position on August 27.

Coronal hole map

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, 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 this method, the extent and intensity of both CHs 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. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet on August 28-29 and quiet to unsettled on August 30-31 due to weak effects from CH531.

Coronal holes (1) Coronal mass ejection (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. 0.5k image [NEW]

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 magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
11546 2012.08.15
2012.08.16
      N17W72           plage
11548 2012.08.17
2012.08.18
      N18W50         plage
11552 2012.08.20
2012.08.21
  2   S17W21 0000   AXX location: S14W36
11553 2012.08.22
2012.08.23
4 11 5 S18E05 0120 DSO HSX

area: 0200

11554 2012.08.23
2012.08.24
6 9 4 N16W27 0110 DAO DAO  
11555 2012.08.24
2012.08.25
10 19 9 N08E43 0320 DHO DAC  
S1875 2012.08.24       N10W32           plage
S1876 2012.08.25   1   N16E06 0000   AXX  
S1877 2012.08.25       N12W10           plage
S1878 2012.08.26       N05W22         plage
11556 2012.08.26
2012.08.27
1 2 1 S12W79 0010 AXX BXO  
S1880 2012.08.26       N28W06         plage
11557 2012.08.27 2 2 2 N17E38 0010 BXO CRO    
11558 2012.08.27 2 3 2 N18E78 0010 BXO AXX    
S1881 2012.08.27   1 1 S19E35 0000   AXX    
S1882 2012.08.27   1   N21E65 0000   AXX    
S1883 2012.08.27   2 2 N13E72 0010   AXX    
S1884 2012.08.27   1   N15E56 0000   AXX    
Total spot count: 25 54 26  
Sunspot number: 85 174 106  (total spot count + 10 * number of spotted regions)
Weighted SN: 45 72 44  (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 51 61 58 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2011.05 95.8 41.6 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.9 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 96.7 61.1 (+1.2) 5.55
2011.12 141.3 73.0 63.4 (+2.3) 3.78
2012.01 132.5 58.3 65.5 (+2.1) 7.15
2012.02 106.5 32.9 (67.4 projected, +1.9) 8.81
2012.03 114.7 64.3 (68.1 projected, +0.7) 16.08
2012.04 113.0 55.2 (67.5 projected, -0.6) 10.10
2012.05 121.5 69.0 (65.8 projected, -1.7) 7.06
2012.06 119.6 64.5 (65.0 projected, -0.8) 10.08
2012.07 133.9 66.5 (66.0 projected, +1.0) 13.90
2012.08 114.4 (1) 72.1 (2A) / 82.8 (2B) (68.6 projected, +2.6) (8.10)

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 quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC 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.