Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 28, 2015 at 06:20 UT.

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data from 2003.01 (September 1, 2015)
Solar cycle Solar cycles 23-24 (September 1, 2015) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (September 1, 2015) Noon SDO sunspot count 1K Reference: 4K (large file) (*)
  Solar cycles 1-24 (July 17, 2015) POES auroral activity level October 2009 - December 2012
  Comparison of cycles 21, 22, 23 and 24 (September 1, 2015) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12, 13, 14, 16 and 24 (September 1, 2015) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs solar cycles (September 16, 2015)  

Recent activity

The geomagnetic field was very quiet on September 27. Solar wind speed at SOHO ranged between 380 and 455 km/s.

Solar flux at 20h UTC on 2.8 GHz was 127.5 (increasing 36.5 over the last solar rotation, the measurement may have been slightly flare enhanced). The 90 day 10.7 flux at 1 AU was 106.4. The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.4). Three hour interval K indices: 11100011 (planetary), 11102222 (Boulder).

The background x-ray flux is at the class C1 level.

At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 296) and 9 active regions using 1K resolution (SN: 178) SDO images on the visible solar disk.

Region 12420 [N09W20] decayed slowly and quietly.
Region 12421 [N15W36] decayed quickly and was mostly quiet.
Region 12422 [S20W14] developed gaining penumbral area and becoming even more complex magnetically. Further M class flares are likely and there is a minor chance of an X class event.
Region 12423 [S09W66] displayed quick growth gaining many spots with a large increase in penumbral area. The region became much more complex as 3 magnetic deltas formed. Further M class flaring is possible. The region produced an M3.6 flare at 03:55 UT on September 28.
Region 12424 [N12W56] decayed slowly and quietly.
Region 12425 [S05W28] decayed slowly and quietly.
Region 12426 [N17E49] decayed slowly and quietly.
New region 12427 [N17E49] emerged rapidly with many spots and weak polarity intermixing. C flares are possible. If current development continues a minor M class flare will become possible.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4781 [S19E38] was quiet and stable.
New region S4784 [S05W50] emerged with penumbra spots.
New region S4785 [N65W05] emerged with a tiny spot at a high latitude.
New region S4786 [S10W19] emerged with a tiny spot.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
C2.1 07:58 S21W07 12422 GOES15  
M1.9/1F 10:40 S22W08 12422 GOES15 Flare in 12423 as well at the same time
C4.0 11:11 S21W11 12422 SDO/EVE  
C2.4 12:26 S21W08 12422 GOES15  
C2.4 12:52 S20W12 12422 GOES15  
C2.2 13:46   12422 GOES15 Flare in 12423 a few minutes later
C5.4 15:38 S20W16 12422 GOES15  
C2.0 16:16   12422 GOES15  
C4.3 16:49 S09W63 12423 GOES15 Most likely source, activity in 12422 as well
C4.2 17:46 S21W11 12422 GOES15  
C4.1/1F 18:53 S09W64 12423 GOES15  
C9.3/1N 19:58   12422 GOES15 SWPC reports a C9.4 recorded by GOES13 at exactly the same time and thereby counts one flare twice
M1.0/1N 21:00 S21W16 12422 GOES15  
C7.7 21:12   12423 SDO/EVE SWPCs flare definition makes it difficult for them to separate events occurring in different places and closely spaced in time
C3.1 21:51   12423 SDO/EVE  
C7.9 23:29 S21W14 12422 GOES15  

Flare activity (SDO/EVE/ESP XRS-B proxy)

Coronal mass ejections (CMEs)

September 25-27: No obviously Earth directed CMEs were observed in available LASCO 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 northern hemisphere coronal hole (CH692) could rotate into an Earth facing position on September 29. A small coronal hole between ARs 12425 and 12422 was in a potentially geoeffective position on September 26 and could cause a brief disturbance on September 29. A northern hemisphere coronal hole (CH693) was in an Earth facing position on September 26-27, however, it is uncertain if this CH is too far to the north to cause a geomagnetic disturbance.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on September 28. Quiet is likely on September 29-30 as well, however, there is some uncertainty as CH693 could cause unsettled and active intervals if it isn't too far to the north.

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: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% 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 overlays
Comment
SWPC Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
12420 2015.09.19
2015.09.20
11 38 18 N11W17 0110 FAI EAO beta-gamma

area: 0170

location: N09W20

12421 2015.09.20
2015.09.22
11 24 13 N16W35 0100 DAI DRI area: 0060
12423 2015.09.21
2015.09.23
14 21 13 S09W65 0100 DAI EAC

beta-gamma-delta

area: 0250

12422 2015.09.22 25 55 27 S20W16 0650 EKC FKC beta-gamma-delta

area: 0950

location: S20W14

12425 2015.09.23
2015.09.25
1 4 1 S05W27 0000 AXX BXO area: 0007
12426 2015.09.24
2015.09.25
1 3 2 N16E22 0010 AXX HRX  
S4780 2015.09.24       N30E10            
12424 2015.09.25 1 2 1 N12W56 0010 AXX BXO  
S4781 2015.09.26   1   S19E38 0001   AXX  
S4782 2015.09.26       N25W21          
12427 2015.09.27 10 24 12 N18E49 0030 CRO DRI   beta-gamma

area: 0110

S4784 2015.09.27   2 1 S05W50 0020   AXX    
S4785 2015.09.27   1   N65W05 0001   AXX    
S4786 2015.09.27   1   S10W19 0002   AXX    
Total spot count: 74 176 88  
Sunspot number: 154 296 178  (total spot count + 10 * number of spotted regions)
Weighted SN: 102 205 117  (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): 169 163 151 k * (sunspot number)
As of July 1, 2015: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.85 for MSN 1K (MSN=Magnetic Sunspot Number)

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO) (4)
Smoothed sunspot number (4) Average ap
(3)
Measured 1 AU
2014.02 170.3
(cycle peak)
166.3 146.1 (cycle peak) 110.5 (+1.2) 10.70
2014.04 143.9 144.8 112.5 116.4 (+2.1) (solar max) 7.88
2014.05 129.7 132.9 112.5 115.0 (-1.4) 5.75
2014.06 122.0 125.8 102.9 114.1 (-0.9) 6.72
2014.07 137.4 141.8 100.2 112.6 (-1.5) 4.50
2014.08 124.7 127.9 106.9 108.3 (-4.3) 7.71
2014.09 146.6 148.1 130.0 101.9 (-6.4) 9.78
2014.10 153.4 152.9 90.0 97.4 (-4.5) 8.96
2014.11 154.8 151.4 103.6 95.0 (-2.4) 9.33
2014.12 158.7 153.8 112.9 92.6 (-2.4) 11.24
2015.01 141.9 137.3 93.0 89.8 (-2.8) 9.46
2015.02 129.1 126.0 66.7 86.6 (-3.2) 9.92
2015.03 125.9 124.6 54.5 (82.1 projected, -4.5) 16.14
2015.04 128.8 129.7 78.0 (78.0 projected, -4.1) 10.73
2015.05 120.0 122.6 90.0 (75.3 projected, -2.7) 8.29
2015.06 122.3 126.1 68.3 (71.6 projected, -3.7) 13.15
2015.07 107.0 110.8 66.4 (67.9 projected, -3.7) 8.83
2015.08 105.4 108.0 64.6 (66.7 projected, -1.2) 14.58
2015.09 (98.7)   61.9 (2A) / 68.7 (2B) / 81.5 (2C) (67.0 projected, +0.3) (17.1)

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).
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 GFZ Potsdam WDC ap indices.
4) Updated to new data set from WDC-SILSO on July 1, 2015

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 Universal Time. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.