Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 29, 2013 at 03:05 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 quiet to active on August 28. Solar wind speed at SOHO ranged between 361 and 465 km/s, early in the day under the influence of a coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 108.1 (decreasing 4.0 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.3). Three hour interval K indices: 43211101 (planetary), 53222211 (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 11828 [N18W44] decayed slowly and quietly.
Region 11834 [N14E22] developed slowly and quietly.
Region 11835 [S10E28] was quiet and stable.
Region 11836 [N11E57] was quiet and stable.

Spotted regions not numbered by SWPC:
S2639 [S15E11] was quiet and stable.
New region S2644 [S13W45] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

August 26-28: 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.

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 29. On August 30-31 quiet to unsettled conditions are likely as a high speed stream from CH582 becomes geoeffective, active intervals are possible.

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
      S19W63         plage
11828 2013.08.18
2013.08.19
  2   N05W54 0003   BXO

location: N18W44

SWPC/USAF location way off for fourth consecutive day

S2621 2013.08.19       N20W55           plage
11833 2013.08.22
2013.08.23
      N18W63           plage
S2629 2013.08.23       N07W14           plage
S2630 2013.08.23       N07W55           plage
11834 2013.08.23
2013.08.24
6 27 7 N14E21 0020 CRO CRI

area: 0070

11835 2013.08.24 6 22 5 S11E26 0280 DKO DHO

area: 0430

S2633 2013.08.24       S10E18           plage
S2634 2013.08.24       N02W46           plage
S2635 2013.08.24       N02W50           plage
S2636 2013.08.25       N08W51           plage
11836 2013.08.26
2013.08.27
2 4 2 N10E55 0140 HAX CAO area: 0170
S2638 2013.08.26       S20W03           plage
S2639 2013.08.26   5   S15E11 0008   AXX  
S2640 2013.08.26       S16W27           plage
S2641 2013.08.26       N27W44           plage
S2643 2013.08.27       N03E09         plage
S2644 2013.08.28   1   S13W45 0003   AXX    
Total spot count: 14 61 14  
Sunspot number: 44 121 44  (total spot count + 10 * number of spotted regions)
Weighted SN: 32 79 32  (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 42 24 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
2013.08 115.4 (1) 84.5 (2A) / 93.6 (2B) / 60.8 (2C) (57.6 projected, -0.1) (8.02)

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.