Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 20, 2013 at 02:45 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 quiet on August 19. Solar wind speed at SOHO ranged between 392 and 472 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 128.3 (increasing 21.6 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 21111111 (planetary), 22112211 (Boulder).

The background x-ray flux was at the class B5 level.

At midnight UTC the visible solar disk had 14 spotted active regions (in 2K resolution SDO images).

Region 11818 [S06W62] was mostly quiet. An M class flare is still possible due to the magnetic delta structure in the northern part of the large penumbra.
Region 11820 [S13W20] developed quickly as new flux emerged. The region has polarity intermixing.
Region 11822 [S09E04] was quiet and stable.
Region 11823 [S07E18] gained a few spots and has weak polarity intermixing.
Region 11824 [S13W40] decayed slowly and quietly.
Region 11825 [N15W27] matured with minor polarity intermixing still observed. C flares are possible.
Region 11827 [S19E59] was quiet and stable.
New region 11828 [N14E68] rotated into view on August 18 and was numbered by SWPC the next day.

Spotted regions not numbered by SWPC:
S2601 [S08W07] was quiet and stable.
S2611 [S11E52] reemerged with a pneumbra spot.
S2617 [N14E03] decayed slowly and quietly.
S2620 [S12E17] developed slowly and quietly.
New region S2621 [N20E62] emerged with a penumbra spot.
New region S2622 [S28W20] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

August 18-19: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
August 17: An asymmetric full halo CME was observed after the M class events in AR 11818. The core of the CME was likely not Earth directed, however, a glancing blow is possible on August 20.

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 trans equatorial coronal hole (CH580) was in an Earth facing position on August 18-19. A coronal hole (CH581) in the northern hemisphere will likely rotate into an Earth facing position on August 22.

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 to active on August 20 due to weak CME effects. Quiet to active conditions are likely on August 21-22 as a high speed stream from CH580 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
11817 2013.08.08
2013.08.10
3     S19W88 0060 CSO     rotated out of view
11819 2013.08.09
2013.08.10
      S16W74           plage
11818 2013.08.09
2013.08.10
3 4 2 S04W61 0250 HKX DKC beta-delta

location: S06W62

11820 2013.08.11
2013.08.13
5 24 11 S12W19 0010 BXO DRI area: 0110
S2599 2013.08.12       N20W49           plage
S2601 2013.08.13   4 2 S08W07 0011   BXO  
S2602 2013.08.13       N20W29         plage
11823 2013.08.14
2013.08.15
4 7 4 S08E17 0170 CSO CSO  
S2605 2013.08.14       S22W57           plage
11822 2013.08.15 3 9   S11W00 0010 BXO BXO location: S09E04

area: 0006

S2608 2013.08.16       S21W07           plage
S2609 2013.08.16       S29W28           plage
11824 2013.08.17 9 10 3 S14W40 0120 DAO DSO area: 0100
11827 2013.08.17
2013.08.18
8 7 6 S18E58 0300 DAO DSC  
S2611 2013.08.17   1   S10E52 0001   AXX    
11826 2013.08.17
2013.08.18
2     N13E01 0010 AXX     spotless, however, SWPC/USAF moved this region to the location of AR S2617

real location: N08E07

S2613 2013.08.17       N22W16         plage
S2614 2013.08.17       S16W59           plage
11825 2013.08.17
2013.08.18
20 31 11 N17W27 0070 DAI DAI beta-gamma

area: 0130

11828 2013.08.18
2013.08.19
4 12 6 N15E65 0030 CAO CSO area: 0090
S2617 2013.08.18   1 1 N14E03 0006   AXX  
S2619 2013.08.18       N05W45         plage
S2620 2013.08.18   7 3 S12E17 0023   DRO split off from AR 11823
S2621 2013.08.19   1   N20E62 0004   AXX    
S2622 2013.08.19   1   S28W02 0003   AXX    
Total spot count: 61 119 49  
Sunspot number: 161 259 149  (total spot count + 10 * number of spotted regions)
Weighted SN: 101 160 90  (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): 97 91 82 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
2013.08 113.3 (1) 58.6 (2A) / 95.6 (2B) / 57.0 (2C) (57.6 projected, -0.1) (7.41)

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.