Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 30, 2013 at 05:05 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update August 1, 2013)] [Cycle 24 progress (last update August 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 4, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated August 20, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was very quiet on August 29. Solar wind speed at SOHO ranged between 310 and 370 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 108.8 (decreasing 4.1 over the last solar rotation). The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.6). Three hour interval K indices: 00000001 (planetary), 10112211 (Boulder).

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

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11834 [N13E08] developed slowly and quietly.
Region 11835 [S09E15] decayed as the large penumbra split off the southern part.
Region 11836 [N11E43] was mostly unchanged and produced a single lowl level C flare. A long duration C8.3 event peaked at 02:46 UTC on August 3. This event was associated with a full halo CME in STEREO-A.

Spotted regions not numbered by SWPC:
S2639 [S12W00] was quiet and stable.
S2643 [N02W04] reemerged with penumbra spots.
New region S2645 [N33E48] emerged with a penumbra spot.

A large filament eruption in the southern hemisphere was observed early in the day. The associated CME will probably not reach Earth.

Coronal mass ejections (CMEs)

August 27-29: 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 coronal hole (CH582) in the northern hemisphere rotated across the central meridian on August 27. A recurrent trans equatorial coronal hole (CH583) will likely rotate into an Earth facing positin on August 31 and September 1.

Coronal hole map

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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 30-31 due to a high speed stream from CH582, active intervals are possible. Late on September 1 or sometime on September 2 a CME associatyed with the C8 LDE in AR 11836 could reach Earth and cause unsettled to minor storm conditions.

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 2K resolution) Compare to the previous day's image. 0.5k image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue 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
11827 2013.08.17
2013.08.18
      S19W77           plage
11828 2013.08.18
2013.08.19
      N05W68        

plage

location: N18W57

SWPC/USAF location way off for fifth consecutive day

11833 2013.08.22
2013.08.23
      N18W77           plage
S2629 2013.08.23       N07W27           plage
11834 2013.08.23
2013.08.24
15 35 19 N14E07 0040 DAI DRI

 

11835 2013.08.24 7 11 5 S10E13 0250 DKO DHO

area: 0380

S2633 2013.08.24       S10E05           plage
S2634 2013.08.24       N02W59           plage
11836 2013.08.26
2013.08.27
3 5 2 N12E42 0160 HAX CAO  
S2638 2013.08.26       S20W16           plage
S2639 2013.08.26   4 2 S12W00 0011   AXX  
S2640 2013.08.26       S16W40           plage
S2641 2013.08.26       N27W57           plage
S2643 2013.08.27   4   N02W04 0007   AXX    
S2644 2013.08.28       S13W58         plage
S2645 2013.08.29   1   N33E48 0002   AXX    
Total spot count: 25 60 28  
Sunspot number: 55 120 68  (total spot count + 10 * number of spotted regions)
Weighted SN: 45 78 46  (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): 33 42 37 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)
2011.11 153.5 (cycle peak) 96.7 (cycle peak) 61.1 (+1.2) 5.55
2012.02 106.5 32.9 66.9 (+1.4)
likely cycle 24 max
8.81
2012.05 121.5 69.0 61.7 (-2.9) 7.06
2012.06 119.6 64.5 58.9 (-2.8) 10.08
2012.07 133.9 66.5 57.8 (-1.1) 13.90
2012.08 115.4 63.0 58.2 (+0.4) 7.96
2012.09 122.9 61.4 58.1 (-0.1) 8.07
2012.10 123.3 53.3 58.6 (+0.5) 9.97
2012.11 121.3 61.8 59.7 (+1.1) 7.08
2012.12 108.6 40.8 59.6 (-0.1) 3.44
2013.01 127.1 62.9 58.7 (-0.9) 4.69
2013.02 104.3 38.0 (57.8 projected, -0.9) 6.11
2013.03 111.3 57.9 (57.3 projected, -0.5) 10.56
2013.04 124.8 72.4 (57.3 projected, 0.0) 5.40
2013.05 131.4 78.7 (57.3 projected, 0.0) 9.73
2013.06 110.1 52.5 (57.6 projected, +0.3) 12.60
2013.07 115.5 57.0 (57.7 projected, +0.1) 9.47
2013.08 115.1 (1) 86.3 (2A) / 92.2(2B) / 60.2 (2C) (57.6 projected, -0.1) (7.80)

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) Boulder SN current month average to date. 2C) STAR SDO 1K Wolf number 30 day average.
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 the 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.