Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 17, 2012 at 04:50 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 16. Solar wind speed at SOHO ranged between 428 and 514 km/s. A disturbance arrived near 04h UT and caused weak to moderate southward Bz (IMF), particularly during the latter half of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 98.3 (increasing 6.0 over the last solar rotation). The Potsdam WDC planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 13.0). Three hour interval K indices: 32213433 (planetary), 33223322 (Boulder).

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

At midnight UTC the visible solar disk had 5 spotted active regions (in 2K resolution SDO images).

Region 11543 [N22W47] decayed slowly and produced the only C flare of the day,  long duration C3.6 event peaking at 13:16 UTC. This event was associated with a partial halo CME.
New region 11546 [N16E73] rotated into view on August 15 and was numbered the next day by SWPC.

Spotted regions not numbered by SWPC:
New region S1860 [N05E37] emerged quickly with several spots.
New region S1861 [N23E36] emerged with a tiny spot.
New region S1862 [N13W12] emerged with two spots.

Coronal mass ejections (CMEs)

August 15-16: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
August 14: A partial halo CME was observed in LASCO imagery following a C3 event in AR 11543 early in the day. A weak glancing blow is possible on August 17.

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 to good.


The geomagnetic field is expected to be quiet to active on August 17-19, first due to CME effects, then effects from CH529.

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

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
11542 2012.08.06 1     S11W62 0000 AXX    


11543 2012.08.06
2 10 7 N22W48 0360 HHX CHO beta-gamma

area: 0420

S1855 2012.08.12       S24W55           plage
S1856 2012.08.14       N13E03         plage
S1857 2012.08.14       S19W30           plage
S1858 2012.08.14       N08W58           plage
11546 2012.08.15
1 1 1 N16E69 0050 HSX HSX location: N16E73
S1860 2012.08.16   12 8 N05E37 0020   DRI    
S1861 2012.08.16   1   N23E36 0000   AXX    
S1862 2012.08.16   2 2 N13W12 0000   BXO    
Total spot count: 4 26 18  
Sunspot number: 34 76 58  (total spot count + 10 * number of spotted regions)
Weighted SN: 19 44 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): 20 27 32 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 33.1 (67.4 projected, +1.9) 8.81
2012.03 114.7 64.2 (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
2012.08 124.1 (1) 49.7 (2A) / 96.3 (2B) (68.6 projected, +2.6) (7.88)

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.