Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 12, 2013 at 04:20 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 on September 11. Solar wind speed at SOHO ranged between 339 and 392 km/s, weakly under the influence of a low speed stream associated with CH584.

Solar flux measured at 20h UTC on 2.8 GHz was 92.8 (decreasing 29.9 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: 5.3). Three hour interval K indices: 20121122 (planetary), 21122312 (Boulder).

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

At the time of counting spots (see image time) there were 12 active regions in 2K resolution (SN: 156) and 7 active regions in 1K resolution (SN: 85) SDO images with spots on the visible solar disk.

Region 11838 [S05W09] developed slowly in the leading polarity area.
Region 11839 [S12W40] decayed and was quiet.
New region 11840 [S12W03] emerged on September 5 and was numbered by SWPC 6 days later. The region decayed on September 11.
New region 11841 [S05E69] rotated into view on September 10 and got its NOAA number the next day.

Spotted regions not numbered by SWPC:
S2667 [S18E37] lost the leader spot and gained a trailing penumbra spot.
S2670 [N04W47] developed slowly.
S2671 [S32W23] gained a leader penumbra spot.
New region S2672 [S11W26] emerged with a couple of spots.
New region S2673 [N08W16] emerged with a penumbra spot.
New region S2674 [N14E37] emerged with penumbra spots in an old plage area.
New region S2675 [N20E36] emerged with a penumbra spot.
New region S2676 [N24E02] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

September 9-11: 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.

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

Forecast

The geomagnetic field is expected to be quiet to active on September 12-14 with a chance of minor storm intervals due to effects from CH585.

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 9 2 S04W13 0010 AXX CRO

location: S05W09

area: 0020

11840 2013.09.05
2013.09.11
5 5 3 S12W03 0020 CRO CRO  
S2660 2013.09.05       N13W58           plage
S2661 2013.09.05       S22W27           plage
S2664 2013.09.08       S03W41           plage
S2665 2013.09.08       S15W18         plage
S2666 2013.09.09       S18W56           plage
11839 2013.09.10 4 4 3 S12W40 0020 CRO CRO area: 0016
S2667 2013.09.10   1 1 S18E37 0003   AXX  
11841 2013.09.10
2013.09.11
1 2 1 S05E69 0030 HSX HSX area: 0060
S2669 2013.09.10       N13E44         plage
S2670 2013.09.10   4 3 N04W47 0030   DRO  
S2671 2013.09.10   2   S32W23 0003   AXX  
S2672 2013.09.11   2 2 S11W26 0009   BXO    
S2673 2013.09.11   1   N08W16 0002   AXX    
S2674 2013.09.11   4   N14E37 0004   BXO    
S2675 2013.09.11   1   N20E36 0003   AXX    
S2676 2013.09.11   1   N24E02 0004   AXX    
Total spot count: 13 36 15  
Sunspot number: 53 156 85  (total spot count + 10 * number of spotted regions)
Weighted SN: 24 53 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): 32 55 47 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
2013.09 101.1 (1) 19.0 (2A) / 51.8 (2B) / 50.8 (2C) (57.8 projected, -0.4) (5.48)

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.