Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 15, 2012 at 02:05 UTC.

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[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 6, 2012)]
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[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 14. Solar wind speed at SOHO ranged between 437 and 502 km/s under the influence of a high speed stream from CH527/CH528.

Solar flux measured at 20h UTC on 2.8 GHz was 105.8 (decreasing 3.7 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.1). Three hour interval K indices: 22221113 (planetary), 23222222 (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 11542 [S12W33] decayed slowly and was mostly quiet. The region was the source of a long duration C1.1 event peaking at 03:01 UTC. A small possibly Earth directed CME was observed in STEREO imagery.
Region 11543 [N22W20] developed a weak magnetic delta structure in the southwestern part of the large penumbra. A minor M class flare is possible. A C3.5 flare was recorded at 00:31 UTC. A small CME was observed in both LASCO and STEREO imagery. The core of the CME is not Earth directed.

Spotted regions not numbered by SWPC:
New region S1856 [N12E27] emerged with a small spot.
New region S1857 [S19W04] emerged with a tiny spot.
New region S1858 [N08W32] emerged with small spots.

Coronal mass ejections (CMEs)

August 12-13: 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 will likely become 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 unsettled on August 15 and quiet on Augusut 16. A weak CME impact is possible on August 17 and could cause a few unsettled and active intervals. A high speed stream from CH529 could cause unsettled to active conditions on August 18-19.

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 4 7 2 S12W33 0040 CAO CRO


11543 2012.08.06
7 21 8 N22W19 0250 CKO DHO beta-gamma-delta

area: 0450

11544 2012.08.08

location: S31W68


11545 2012.08.09
3     S14W63 0010 AXX CRO   spotless
S1852 2012.08.10       N16W45           plage
S1853 2012.08.11       S25W39           plage
S1854 2012.08.11       S01W53           plage
S1855 2012.08.12       S24W29           plage
S1856 2012.08.14   1 1 N12E27 0000   AXX    
S1857 2012.08.14   1   S19W04 0000   AXX    
S1858 2012.08.14   3 2 N08W32 0010   BXO    
Total spot count: 14 33 13  
Sunspot number: 44 83 53  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 26 49 29  (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): 26 29 29 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
2012.08 127.6 (1) 47.5 (2A) / 105.3 (2B) (68.6 projected, +2.6) (7.64)

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.