Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 20, 2013 at 05:05 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 unsettled on September 19. Solar wind speed at SOHO ranged between 463 and 559 km/s under the influence of a high speed stream.

Solar flux measured at 20h UTC on 2.8 GHz was 107.9 (decreasing 16.2 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 114.6. The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 10.8). Three hour interval K indices: 33332122 (planetary), 23442322 (Boulder).

The background x-ray flux was at the class B3 level.

At the time of counting spots (see image time) there were 11 active regions in 2K resolution (SN: 150) and 7 active regions in 1K resolution (SN: 90) SDO images with spots on the visible solar disk.

Region 11841 [S03W37] decayed slowly and quietly.
Region 11843 [N01W21] decayed slowly and quietly.
Region 11845 [S17E36] decayed slowly and quietly.
Region 11846 [S18E49] was mostly unchanged and could produce occasional C flares.
Region 11847 [N11E47] decayed and could become spotless today.
New region 11848 [S10E36] emerged with spots. This area had spots on September 16-17, then became spotless on September 18.
New region 11849 [N20E32] emerged with several spots.
New region 11850 [N08E78] rotated into view and appears to have polarity intermixing. C flares are possible.

Spotted regions not numbered by SWPC:
New region S2700 [S20E24] emerged with a penumbra spot.
New region S2701 [N16W37] emerged with penumbra spots.
New region S2702 [S11W48] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

September 16-18: 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 (CH587) in the northern hemisphere will likely rotate into an Earth facing position on September 19-20.

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 20-23 due to coronal hole high speed streams.

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
11841 2013.09.10
2013.09.11
1 2 2 S04W38 0010 HRX HRX

location: S03W37

area: 0022

S2684 2013.09.15       S31W14           plage
11848 2013.09.16
2013.09.19
1 4 1 S10E36 0010 AXX BXO   area: 0015
11845 2013.09.16
2013.09.17
1 3   S18E34 0010 AXX BXO area: 0004
11847 2013.09.16
2013.09.17
  1   N11E41 0002   AXX location: N11E47
11843 2013.09.16
2013.09.17
6 12 8 N01W21 0060 DSO CSO area: 0090
11844 2013.09.16
2013.09.17
      N24W84           plage
S2690 2013.09.16       S12W52           plage
11846 2013.09.17 2 6 2 S16E49 0180 CSO DSO area: 0220
S2692 2013.09.17       N22W01           plage
S2693 2013.09.17       N19W18           plage
S2694 2013.09.17       N06E02           plage
S2695 2013.09.17       S34W08           plage
S2697 2013.09.17       S21W54           plage
S2698 2013.09.17       S16W34           plage
S2699 2013.09.18       S20W03         plage
11849 2013.09.19 3 4 3 N22E32 0010 BXO CRO   area: 0018
11850 2013.09.19 1 4 3 N09E75 0010 AXX EAO   area: 0070
S2700 2013.09.19   1 1 S20E24 0004   AXX    
S2701 2013.09.19   2   N16W37 0005   BXO    
S2702 2013.09.19   1   S11W48 0002   AXX    
Total spot count: 15 40 20  
Sunspot number: 85 150 90  (total spot count + 10 * number of spotted regions)
Weighted SN: 28 61 41  (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): 51 53 50 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 99.3 (1) 31.7 (2A) / 50.1 (2B) / 39.7 (2C) (57.8 projected, -0.4) (5.89)

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.