Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 14, 2013 at 05:55 UTC.

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

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated September 5, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to active on September 13. Solar wind speed at SOHO ranged between 415 and 534 km/s under the influence of a high speed stream from CH585.

Solar flux measured at 20h UTC on 2.8 GHz was 91.6 (decreasing 31.6 over the last solar rotation). The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 8.8). Three hour interval K indices: 31212421 (planetary), 31*****1 (Boulder).

The background x-ray flux was at the class B1 level.

At the time of counting spots (see image time) there were 10 active regions in 2K resolution (SN: 132) and 5 active regions in 1K resolution (SN: 59) SDO images with spots on the visible solar disk.

Region 11838 [S05W37] decayed slowly and quietly.
Region 11839 [S12W69] decayed slowly and quietly.
Region 11840 [S11W32] was quiet and stable.
Region 11841 [S04E43] was quiet and stable.

Spotted regions not numbered by SWPC:
S2674 [N13E08] was quiet and stable.
New region S2678 [S12E12] emerged with a penumbra spot.
New region S2679 [N15E01] emerged with penumbra spots.
New region S2680 [N18W43] emerged with a penumbra spot.
New region S2681 [S16W03] emerged with penumbra spots in an old plage area.
New region S2682 [S09E11] emerged with penumbra spots in an old plage area.

Coronal mass ejections (CMEs)

September 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 (CH585) in the northern hemisphere was in an Earth facing position on September 9-11. A trans equatorial coronal hole (CH586) was in an Earth facing position on September 13-14.

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 unsettled on September 14-15 due to effects from CH585. Effects from CH586 could cause quiet to active conditions on September 16-17.

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
11838 2013.09.04
2013.09.05
  3 1 S05W40 0009   AXX

location: S05W37

11840 2013.09.05
2013.09.11
  5 3 S11W33 0010 AXX BXO  
S2661 2013.09.05       S22W53           plage
S2665 2013.09.08       S15W44           plage
11839 2013.09.10 6 4 2 S12W66 0030 CRO CRO

location: S12W69

S2667 2013.09.10       S18E11           plage
11841 2013.09.10
2013.09.11
3 4 2 S06E41 0050 CSO CSO

location: S04E43

S2669 2013.09.10       N13E18           plage
11842 2013.09.10
2013.09.12
1     N04W76 0010 AXX     spotless
S2671 2013.09.10       S32W49           plage
S2672 2013.09.11       S11W52           plage
S2673 2013.09.11       N08W42           plage
S2674 2013.09.11   2   N13E08 0004   BXO  
S2675 2013.09.11       N20E10           plage
S2676 2013.09.11       N24W24           plage
S2677 2013.09.12       S28W05         plage
S2678 2013.09.13   1 1 S12E12 0006   AXX    
S2679 2013.09.13   2   N15E01 0004   BXO    
S2680 2013.09.13   1   N18W43 0003   AXX    
S2681 2013.09.13   7   S16W03 0008   AXX    
S2682 2013.09.13   3   S09E11 0006   BXO    
Total spot count: 10 32 9  
Sunspot number: 40 132 59  (total spot count + 10 * number of spotted regions)
Weighted SN: 18 40 17  (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): 24 46 32 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 58.4 (-0.3) 6.11
2013.03 111.3 57.9 (58.2 projected, -0.2) 10.56
2013.04 124.8 72.4 (57.9 projected, -0.3) 5.40
2013.05 131.4 78.7 (58.0 projected, +0.1) 9.73
2013.06 110.1 52.5 (58.3 projected, +0.3) 12.60
2013.07 115.5 57.0 (58.3 projected, 0.0) 9.47
2013.08 114.6 66.0 (58.2 projected, -0.1) 8.27
2013.09 99.8 (1) 22.3 (2A) / 51.4 (2B) / 48.8 (2C) (57.8 projected, -0.4) (5.88)

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.