Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 19, 2012 at 04:05 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 18. Solar wind speed at SOHO ranged between 334 and 458 km/s. Effects from CH529 became noticable after 14h UTC with solar wind speed increasing slowly from 360 km/s at 18h to above 450 km/s by the end of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 97.0 (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 B3 level.

At 06 UTC (due to image processing lag HMI imagery at 06h UTC were the latest available at the time of writing this) the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11543 [N23W73] lost penumbral area, however, the single penumbra is interesting with positive polarity flux emerging in its center.
Region 11546 [N16E46] was quiet and stable.
Region 11547 [N06E09] decayed slowly and quietly.
New region 11548 [N19E73] rotated partly into view on August 17. The region has been very active and the source of 5 impulsive M flares and many C flares during the day. Further M class flaring is likely. Flares above the C5 level: major M5.5 at 01:02, M1.8 at 03:23, C6.1 at 06:18, C7.3 at 14:27, M2.0/1N at 16:07, M1.0 at 22:54, M1.3 at 23:22 UTC.

Spotted regions not numbered by SWPC:
S1862 [N13W38] developed slowly and quietly.
New region S1866 [S18W11] emerged with tiny spots in an old plage area.

Coronal mass ejections (CMEs)

August 16, 18: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
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.


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.


The geomagnetic field is expected to be quiet to active on August 19 due to effects from CH529. On August 20-21 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
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
2K 1K
11543 2012.08.06
3 6 2 N23W74 0300 HHX CKO


S1856 2012.08.14       N13W23           plage
S1857 2012.08.14       S19W56           plage
11546 2012.08.15
1 1 1 N16E44 0050 HSX HSX location: N16E46

area: 0090

11547 2012.08.16
2 6 3 N06E09 0010 CRO DRO  
S1861 2012.08.16       N23E10           plage
S1862 2012.08.16   5 3 N13W38 0010   BXO  
11548 2012.08.17
8 6 4 N20E76 0120 CAO DAO  
S1865 2012.08.17       S28E04         plage
S1866 2012.08.18   2   S18W11 0000   AXX    
Total spot count: 14 26 13  
Sunspot number: 54 86 63  (total spot count + 10 * number of spotted regions)
Weighted SN: 37 49 36  (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): 32 30 35 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
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
2012.08 121.0 (1) 52.8 (2A) / 90.9 (2B) (68.6 projected, +2.6) (8.15)

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.