Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 10, 2017 at 08:10 UT.

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data since 2003.01 (September 9, 2017)
Solar cycle Solar cycles 23-24 (September 1, 2017) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (September 1, 2017) / Cycle 25 spots (new) Noon SDO sunspot count 1K / 4K (*)
  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, 2017) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12, 13, 14, 16 and 24 (September 1, 2017) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (July 16, 2017)  

Recent activity

The geomagnetic field was quiet on September 9. Solar wind speed at SOHO ranged between 460 and 702 km/s. Although the main solar wind driver was still the September 6 CME, the interplanetary magnetic field was mostly neutral or northwards resulting in a sharp decrease in geomagnetic activity.

Solar flux at 20h UTC on 2.8 GHz was 107.2 (increasing 39.0 over the previous solar rotation). The average 90 day 10.7 flux at 1 AU was 83.0. 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: 22101000 (planetary), 32311220 (Boulder)

The background x-ray flux is at the class B5 level.

At the time of counting spots (see image time), spots were observed in 7 active regions using 2K resolution (SN: 114) and in 7 active regions using 1K resolution (SN: 92) SDO images on the visible solar disk.

Region 12673 [S09W83] continued to decrease in magnetic complexity and produced fewer and less intense flares than during the previous day. M class flares are possible while the region is transiting the southwest limb.
Region 12674 [N12W70] decayed slowly and quietly.
Region 12677 [N17W13] decayed slowly and quietly.
Region 12678 [N11W06] decayed slowly and quietly.
Region 12679 [N15W53] decayed further and could become spotless today.

Spotted regions not numbered (or interpreted differently) by SWPC:
S5792 [S07W09] was quiet and stable.
New region S5794 [N09E79] rotated into view at noon.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
C6.3 03:09 S11W69 12673 GOES15  
C4.2 04:01   12673 GOES15  
M1.1 04:28 S13W69 12673 GOES15  
M3.7 11:04 S11W70 12673 GOES15  
M3.0 11:28 S14W74 12673 SDO  
C4.7 21:11   12673 GOES15  
M1.1 23:53 S07W74 12673 GOES15  

Coronal mass ejections (CMEs)

September 8-10: 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 (CH824) will rotate across the central meridian on September 10-12.

Propagation

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

Forecast

The geomagnetic field is expected to be quiet September 10-12. Quiet to active conditions are likely on September 13-15 due to effects from CH824.

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). 4K 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
12673 2017.08.28
2017.08.29
8 9 4 S09W83 0530 DKC DKC

beta-gamma-delta

12674 2017.08.28
2017.08.29
7 14 6 N13W67 0560 FKO FKO

location: N12W70

12677 2017.09.02
2017.09.03
  5 2 N17W15 0010   BXO  
12678 2017.09.04
2017.09.05
4 11 6 N11W07 0020 CRO DRO area: 0040
12679 2017.09.05
2017.09.07
  1 1 N15W54 0002   AXX  
S5791 2017.09.06       S09W38            
S5792 2017.09.08   3 2 S07W09 0009   CRO  
S5793 2017.09.08       S06W28          
S5794 2017.09.09   1 1 N09E79 0120   HSX    
Total spot count: 19 44 22  
Sunspot number: 49 114 92  (total spot count + 10 * number of spotted regions)
Weighted SN: 42 75 53  (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): 54 63 74 k * (sunspot number)
As of May 7, 2016: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.80 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
2016.04 93.3 94.0 38.0 47.8 (-2.7) 9.03
2016.05 93.0 95.3 52.1 44.9 (-2.9) 11.65
2016.06 81.9 84.5 20.9 41.6 (-3.3) 8.44
2016.07 86.0 88.9 32.5 38.6 (-3.0) 9.43
2016.08 85.0 87.1 50.7 36.0 (-2.6) 9.61
2016.09 87.7 88.7 44.7 33.3 (-2.7) 14.54
2016.10 86.1 85.6 33.6 31.4 (-1.9) 15.33
2016.11 78.6 76.9 21.4 29.9 (-1.5) 9.11
2016.12 75.1 72.8 18.9 28.5 (-1.4) 9.34
2017.01 77.3 74.9 25.8 27.9 (-0.6) 9.45
2017.02 76.8 75.0 26.1 26.6 (-1.3) 9.58
2017.03 74.6 73.9 17.7 (25.0 projected, -1.6) 14.20
2017.04 80.3 80.8 32.6 (23.4 projected, -1.6) 11.70
2017.05 73.6 75.2 18.8 (22.3 projected, -1.1) 8.09
2017.06 74.7 77.1 19.4 (21.3 projected, -1.0) 6.08
2017.07 77.4 79.9 18.3 (20.2 projected, -1.1) 8.97
2017.08 77.9 79.8 33.1 (18.7 projected, -1.5) 10.66
2017.09 (116.4)   25.3 (2A) / 87.1 (2B) / 53.2 (2C) (17.5 projected, -1.2) (23.0)

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.