Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 7, 2013 at 04:00 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 on August 6. Solar wind speed at SOHO ranged between 389 and 519 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 103.9 (decreasing 14.0 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 21111012 (planetary), 23321222 (Boulder).

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

At midnight UTC the visible solar disk had 11 spotted active regions (in 2K resolution SDO images).

Region 11806 [S13W76] decayed slowly and quietly.
Region 11808 [N14W51] was quiet and stable.
Region 11809 [N12W12] was quiet and stable.
Region 11810 [S26W07] has weak polarity intermixing and was quiet.
Region 11811 [N06W38] reemerged with a penumbra spot.

Spotted regions not numbered by SWPC:
S2587 [N24E08] reemerged with a penumbra spot.
S2588 [S17W34] reemerged with several penumbra spots.
S2590 [S13E07] reemerged with several penumbra spots.
New region S2591 [S26E81] rotated into view.
New region S2592 [S20E77] rotated into view.
New region S2593 [S12W07] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

August 4-6: 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 small trans equatorial coronal hole (CH578) rotated across the central meridian on August 4-5.

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 poor.

Forecast

The geomagnetic field is expected to be quiet on August 7. On August 8 there is a chance of unsettled and active intervals as a stream from CH578 becomes geoeffective.

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
11806 2013.07.26
2013.07.27
1 3 1 S13W77 0030 HSX CRO  
S2574 2013.07.28       S08W43         plage
11808 2013.07.29 1 1 1 N15W54 0040 HSX HSX location: N14W51
11809 2013.07.30 11 23 9 N13W09 0080 CSO CSO

location: N12W12

11810 2013.07.31 8 22 7 S26W06 0050 CAO DAI beta-gamma
S2580 2013.07.31       S15W19           plage
S2581 2013.07.31       S11W11           plage
11811 2013.07.31
2013.08.01
  1   N07W46 0002   AXX  

location: N06W38

S2583 2013.08.01       N07W45         plage
S2584 2013.08.01       S13W48         plage
S2585 2013.08.03       N13E09         plage
S2586 2013.08.03       N17E24         plage
S2587 2013.08.03   1   N24E08 0001   AXX    
S2588 2013.08.03   7 2 S17W34     BXO    
S2589 2013.08.03       N26W55           plage
S2590 2013.08.04   5 4 S13E07     BXO    
S2591 2013.08.06   1   S26E81 0020   HRX    
S2592 2013.08.06   1   S20E77 0003   AXX    
S2593 2013.08.06   1   S12W07 0002   AXX    
Total spot count: 21 66 24  
Sunspot number: 61 176 84  (total spot count + 10 * number of spotted regions)
Weighted SN: 41 87 45  (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): 37 62 46 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)
possible 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
2013.08 107.6 (1) 16.1 (2A) / 83.2 (2B) / 52.5 (2C) (57.6 projected, -0.1) (7.7)

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.