Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 27, 2021 at 19:55 UT. (Update covering September 24)

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 transition using 365d smoothing Research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing

Recent activity

The geomagnetic field was quiet on September 24. The high latitude magnetometer at Andenes recorded quiet to active conditions.

Solar flux density measured at 20h UT on 2.8 GHz was 88.4 - decreasing 1.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 79.25). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.4). Three hour interval K indices: 22211211 (planetary), 22312311 (Boulder), 11111423 (Andenes).

The background x-ray flux is at the class B1 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 8 active regions using 2K resolution (SN: 156) and in 5 active regions using 1K resolution (SN: 93) SDO/HMI images.

Region 12871 [S28W00] was mostly quiet. The northeastern magnetic delta reestablished itself and the region has the potential to produce further M class events.
Region 12872 [N17W11] decayed slowly and quietly.
Region 12873 [N26W58] decayed slowly and quietly.
Region 12875 [S32W60] decayed slowly and quietly.
New region 12876 [S23E05] emerged with a few spots early in the day, then decayed slowly after noon.

Spotted regions not observed (or interpreted differently) by SWPC:
New region S7100 [S22E60] emerged with a tiny spot.
New region S7101 [N19E51] emerged with a few spots.
New region S7102 [N33E48] emerged with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
C2.9 07:01   12871 GOES16  

Coronal mass ejections (CMEs)

September 22-24: 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 trans equatorial coronal hole (CH1032) was Earth facing on September 19-22. A northern hemisphere coronal hole (CH1033) will likely rotate across the central meridian on September 23-24.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is 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 25-27 due to effects from CH1032 and CH1033, occasional minor storm intervals are possible.

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
12871 2021.09.18 8 29 15 S28E01 0140 DAO DSC beta-gamma-delta
12872 2021.09.19
2021.09.20
10| 29 20 N17W12 0080 CAO DRI

 

12873 2021.09.19
2021.09.20
2 3   N25W59 0010 BXO AXX location: N25W45
12874 2021.09.19
2021.09.22
      S25W54          
12875 2021.09.20
2021.09.22
2 2 1 S33W59 0010 BXO AXX area: 0005
S7091 2021.09.21       N17E27            
S7093 2021.09.22       N23W30            
S7094 2021.09.22       N16W23            
S7095 2021.09.22       N21W01            
S7096 2021.09.22       S19E28          
S7097 2021.09.23       N17E28          
S7098 2021.09.23       N17E44          
12876 2021.09.24
2021.09.24
3 7 4 S22E04 0010 BXO BXO area: 0018
S7100 2021.09.24   1   S22E60 0003   AXX    
S7101 2021.09.24   4 3 N19E51 0015   BXO    
S7102 2021.09.24   1   N23E48 0001   AXX    
Total spot count: 25 76 43  
Sunspot number: 75 156 93  (total spot count + 10 * number of spotted regions)
Weighted SN: 35 84 51  (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): 83 86 74  

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 86.0 (1)   41.5 (2A) / 51.9 (2B) / 56.8 (2C) (45.9 projected, +5.7) (7.0)
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

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.