Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 20, 2012 at 03:50 UTC. SDO sunspot info added at 21:50 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 active on August 19. Solar wind speed at SOHO ranged between 345 and 572 km/s. A high speed stream, likely from CH529, was the dominant solar wind source after 08h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 96.2 (increasing 3.3 over the last solar rotation). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.9). Three hour interval K indices: 12222243 (planetary), 12332333 (Boulder).

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

At 22h UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11543 [N23W84] completed the split into several penumbrae.
Region 11546 [N16E33] was quiet and stable.
Region 11547 [N06W03] was quiet and stable.
Region 11548 [N19E61] decayed and only managed to produce a few C flares early in the day.
New region 11549 [S16W30] emerged on August 18 and was numbered the next day by SWPC.

Spotted regions not numbered by NOAA/SWPC:
S1862 [N13W52] was quiet and stable.
New region S1867 [N12E16] emerged with a single spot.
New region S1868 [S12W58] emerged with several spots.

Coronal mass ejections (CMEs)

August 18-19: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. A full halo CME was observed in LASCO from 19:42 UTC on August 19, the source was an intense flare in the southern hemisphere several days behind the southeast limb.
August 17: A large filament eruption near AR 11543 starting at 22h UTC was the source of a wide and bright CME. While the major part of the CME was directed northwards, there may have been a weak Earth directed component. A weak glancing blow is possible on August 21.

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 recurrent coronal hole (CH529) in the southern hemisphere was Earth facing on August 15-16.

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 fair to good.

Forecast

The geomagnetic field is expected to be quiet to active on August 20 due to effects from CH529. On August 21-22 mostly quiet conditions are likely with a chance of weak CME effects on August 21.

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
11543 2012.08.06
2012.08.07
3 3 3 N23W86 0180 DSO DAO

 

S1856 2012.08.14       N13W36           plage
11546 2012.08.15
2012.08.16
1 1 1 N16E28 0050 HSX HSX  
11547 2012.08.16
2012.08.17
3 9 4 N06W04 0020 CSO CRI  
S1861 2012.08.16       N23W03           plage
S1862 2012.08.16   2 2 N13W52 0000   BXO  
11548 2012.08.17
2012.08.18
8 8 5 N19E62 0080 CSO CAO  
S1865 2012.08.17       S28W09           plage
11549 2012.08.18
2012.08.19
3 3 3 S16W30 0020 CSO CRO  
S1867 2012.08.19   1 1 N12E16 0000   AXX    
S1868 2012.08.19   5 2 S12W58 0010   BXO    
Total spot count: 17 32 21  
Sunspot number: 67 112 101  (total spot count + 10 * number of spotted regions)
Weighted SN: 42 53 42  (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): 40 39 56 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
2012.08 119.6 (1) 54.9 (2A) / 89.6 (2B) (68.6 projected, +2.6) (8.46)

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.