Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 11, 2021 at 05:10 UT. The update on September 12 will likely not be until after 15 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, 2021)
Solar cycle Solar cycles 23-25 (August 2, 2021) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (August 2, 2021) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (June 1, 2020) POES auroral activity level October 2009 - December 2012]
  Comparison of cycles 21-25 (August 2, 2021) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (August 2, 2021) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (August 22, 2021) Cycle 25 spots (final update December 25, 2019)
  Solar cycles 24-25 using 365d smoothing Research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing

Recent activity

The geomagnetic field was quiet to unsettled on September 10. The high latitude magnetometer at Andenes recorded quiet to minor storm conditions.

Solar flux density measured at 20h UT on 2.8 GHz was 96.3 - increasing 23.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 78.81). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.1). Three hour interval K indices: 12211133 (planetary), 13312324 (Boulder), 32210255 (Andenes).

The background x-ray flux is at the class B2 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 7 active regions using 2K resolution (SN: 180) and in 5 active regions using 1K resolution (SN: 109) SDO/HMI images.

Region 12863 [S16W80] was quiet and stable.
Region 12864 [N24W75] decayed slowly and quietly.
Region 12866 [S18W18] decayed significantly in the trailing spots section. The region was mostly quiet.
Region 12868 [S20W35] decayed and still has polarity intermixing. The region produced the only C flare of the day, a C1.0 long duration event peaking at 21:34 UT.
Region 12869 [S34W15] decayed slowly and quietly.

Spotted regions not observed (or interpreted differently) by SWPC:
New region S7072 [S10E54] emerged with a tiny spot.
New region S7073 [N07E32] emerged with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
           

Coronal mass ejections (CMEs)

September 9-10: No obviously Earth directed CMEs were observed in available LASCO imagery.
September 8: A CME was observed off the west limb early in the day following a C2 flare late on September 7 in AR 12864. It is uncertain if the CME has an Earth directed component.

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 small northern hemisphere coronal hole (CH1029) was Earth facing on September 9, CH1029 closed on September 10.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high 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 11-13. On September 11 there is a minor chance of a weak CME impact and unsettled to active conditions if any parts of the September 8 CME were Earth directed.

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 officially numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC, all other regions are numbered sequentially as they emerge using the STAR spot number. 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. SWPC data considered to be not sufficiently precise (location, area, classification) are red colored.

Active region SWPC date numbered
STAR detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlays
Comment
SWPC/
USAF
Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
S7057 2021.08.31       N25W53          
12863 2021.09.01
2021.09.02
1 2 1 S15W81 0070 HSX HAX  
12864 2021.09.02
2021.09.03
2 2 1 N24W76 0080 CSO CSO

 

12865 2021.09.03
2021.09.04
      N23W55            
S7062 2021.09.03       N15W26            
12868 2021.09.03
2021.09.05
20 39 21 S22W34 0250 DKI DAI beta-gamma

location: S20W35

area: 0160

12866 2021.09.03
2021.09.04
17 44 27 S18W19 0460 DKC DKC  
12869 2021.09.07
2021.09.08
9 21 9 S34W14 0060 CAO DRI area: 0040
12870 2021.09.08
2021.09.09
      S31E45          
S7069 2021.09.08       N11W05            
S7070 2021.09.09       N28W10          
S7071 2021.09.09       S31W06          
S7072 2021.09.10   1   S10E54 0001   AXX    
S7073 2021.09.10   1   N07E32 0001   AXX    
Total spot count: 49 110 59  
Sunspot number: 99 180 109  (total spot count + 10 * number of spotted regions)
Weighted SN: 84 138 87  (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): 109 99 87  

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO)
Smoothed sunspot number (4) Average ap
(3)
Measured 1 AU
2014.02 170.3
(cycle peak)
166.3 146.1 (cycle peak) 110.5 10.70
2014.04 143.9 144.8 112.5 116.4 (solar max) 7.88
2017.09 91.3 92.3 43.6 18.2 (-1.3) 18.22
(cycle peak)
2019.11 70.2 68.7 0.5 2.0 (-0.6)
(Solar minimum using 365d smoothing:
November 17, 2019)
4.19
2019.12 70.8 68.6 1.6 1.8 (-0.2)
(ISN 13 months smoothed
solar minimum)
3.22
2020.03 70.2 69.5 1.5 3.0 (+0.3) 5.63
2020.04 69.5 70.0 5.4 3.6 (+0.6) 5.32
2020.05 69.0 70.6 0.2 5.6 (+2.0) 3.80
2020.06 69.5 71.7 5.8 7.9 (+2.3) 3.75
2020.07 69.5 71.8 6.3 9.0 (+1.1) 4.28
2020.08 71.6 73.4 7.6 9.5 (+0.5) 5.68
2020.09 70.7 71.4 0.7 10.5 (+1.0) 8.59
2020.10 74.6 74.2 14.6 11.9 (+1.4) 6.13
2020.11 89.9 88.0 34.5 13.6 (+1.7) 4.77
2020.12 86.9 84.2 23.1 15.3 (+1.7) 4.72
2021.01 76.0 73.6 10.4 17.3 (+2.0) 4.39
2021.02 74.3 72.4 8.3 19.1 (+1.8) 9.50
2021.03 76.0 75.2 17.3 (21.4 projected, +2.3) 10.17
2021.04 75.9 76.4 24.5 (25.0 projected, +3.6) 8.40
2021.05 75.3 77.1 21.2 (27.7 projected, +2.7) 6.50
2021.06 79.4 81.8 25.3 (30.9 projected, +3.2) 5.52
2021.07 81.0 83.6 34.4 (35.5 projected, +4.6) 5.51
2021.08 77.7 79.7 22.4 (40.2 projected, +4.7) 6.19
2021.09 93.1 (1)   23.7 (2A) / 71.0 (2B) / 48.2 (2C) (45.9 projected, +5.7) (6.3)
2021.10       (50.3 projected, +4.4)  
2021.11       (54.9 projected, +4.6)  
2021.12       (60.7 projected, +5.8)  
2022.01       (64.3 projected, +3.6)  
2022.02       (69.1 projected, +4.8)  

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz and any corrections applied to that measurement.
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) Source: SIDC-SILSO.

Solar cycles 24-25 transition

Smoothed SF and sunspot numbers

 

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.