Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 14, 2013 at 04:30 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 July 28, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to unsettled on August 13. Solar wind speed at SOHO ranged between 317 and 423 km/s. A disturbance after about 08h UTC was associated with a minor increase in solar wind speed and an increased total field of the interplanetary magnetic field as well as frequent southward excursions of the IMF. This may be associated with a corotating interaction region ahead of the stream from CH579.

Solar flux measured at 20h UTC on 2.8 GHz was 122.0 (increasing 10.7 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: 7.4). Three hour interval K indices: 20121322 (planetary), 20132522 (Boulder).

The background x-ray flux was at the class B6 level.

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

Region 11816 [S19W25] was quiet and stable.
Region 11817 [S21W04] decayed as the opposite polarity fields became better separated. The magnetic delta structure disappeared.
Region 11818 [S07E35] developed further and has acquired a weak magnetic delta structure at the northeast corner of the large penumbra. C and M class flares are possible.
Region 11819 [S18E08] developed slowly and quietly.
New region 11820 [S13E60] rotated into view on August 11 and was numbered by SWPC 2 days later. The region decayed slowly.

Region 11809, just behind the northwest limb, became quite active during the day and produced 5 C flares.

Spotted regions not numbered by SWPC:
S2600 [N03W20] decayed slowly and quietly.
New region S2601 [S08E78] rotated into view.
New region S2602 [N25E45] emerged with a few penumbra spots in an old plage area.

Coronal mass ejections (CMEs)

August 11-13: 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 recurrent coronal hole (CH579) in the northern hemisphere will be rotating across the central meridian on August 11-16.

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

Forecast

The geomagnetic field is expected to be quiet to active with a chance of minor storm intervals on August 14-19 due to effects from CH579.

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
11813 2013.08.04
2013.08.07
      S14W88           plage
11814 2013.08.06
2013.08.07
1     S27W18 0010 HRX     spotless
11816 2013.08.06
2013.08.07
  3   S22W21 0007   AXX location: S19W25
11817 2013.08.08
2013.08.10
22 43 20 S21W04 0240 ESC EAC  
11819 2013.08.09
2013.08.10
4 16 8 S17E07 0020 CRO DRI  
11818 2013.08.09
2013.08.10
17 29 16 S07E21 0340 DHC DKI beta-gamma-delta

area: 0470

S2597 2013.08.10       S21W59           plage
11820 2013.08.11
2013.08.13
4 10 5 S13E60 0060 CSO CRO  
S2599 2013.08.12       N20E29         plage
S2600 2013.08.12   1 1 N03W20 0004   AXX  
S2601 2013.08.13   1 1 S08E78 0006   AXX    
S2602 2013.08.13   2   N25E45 0002   AXX    
Total spot count: 48 105 51  
Sunspot number: 98 185 111  (total spot count + 10 * number of spotted regions)
Weighted SN: 74 126 77  (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): 59 65 61 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
2013.08 108.3 (1) 35.1 (2A) / 83.7 (2B) / 52.7 (2C) (57.6 projected, -0.1) (6.06)

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.