Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 29, 2023 at 06:00 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 3, 2023)
Solar cycle Solar cycles 23-25 (September 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (September 1, 2023) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (July 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (September 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (September 1, 2023) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (July 10, 2023) 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 to unsettled on September 28. Solar wind speed at DSCOVR ranged between 347 and 513 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels. A sudden increase in the total IMF field was observed at 20:47 UT, possibly the arrival of another CME.

Solar flux density measured at 20h UT on 2.8 GHz was 147.8 - increasing 12.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 154.91. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.1). Three hour interval K indices: 23111002 (planetary), 12012222 (Boulder), 34120004 (Andenes).

The background x-ray flux is at the class C1 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 15 active regions using 2K resolution (SN: 242) and in 9 active regions using 1K resolution (SN: 137) SDO/HMI images.

Region 13435 [N09W77] decayed slowly and quietly
Region 13440 [N17W58] decayed slowly and was mostly quiet. C1 flares: C1.6 @ 20:51 UT
Region 13444 [N23W47] was quiet and stable.
Region 13445 [S14W51] decayed slowly and was mostly quiet. C1 flares: C1.6 @ 16:46, C1.4 @ 17:42 UT
Region 13446 [N23W13] was quiet and stable.
Region 13447 [S22W32] decayed slowly and quietly.
Region 13448 [N13E34] was quiet and stable.
Region 13450 [S18E57] developed slowly and was the most active region on the visible disk. Further M class flares are possible. C1 flares: C1.5 @ 03:53, C1.3 @ 05:13, C1.7 @ 10:30, C1.4 @ 15:42 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8993 [N14E23] was quiet and stable.
S8994 [S20E40] was quiet and stable.
S8996 [N16E15] decayed slightly and was mostly quiet. C1 flares: C1.9 @ 10:51 UT
S8997 [S14E10] was quiet and stable.
New region S8999 [N25E10] was observed with tiny spots in an old plage area.
New region S9000 [S20W08] was observed with tiny spots in an old plage area.
New region S9001 [S28E09] was observed with tiny spots in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C5.3 00:19 S19E68 13450 GOES16  
C3.0 04:03   13450 GOES16  
C3.4 06:11   13450 GOES18  
M1.3 09:07 S18E65 13450 GOES16  
C2.4 12:33   13450 GOES16  
C3.0 14:04 S23E72 13450 GOES16  
C2.6 17:15 S10W42 13445 GOES16  

Coronal mass ejections (CMEs)

September 26-28: No obviously Earth directed CMEs were observed.

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]

No obvious coronal holes are currently in an Earth facing position.

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 poor.

Forecast

The geomagnetic field is likely to be quiet to unsettled on September 29 - October 1 with a chance of active intervals on September 29.

Coronal holes (1) Coronal mass ejections (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 colored red.

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
13435 2023.09.16
2023.09.16
3 5 3 N10W77 0090 CSO HAX

area: 0180

location: N09W77

13439 2023.09.17
2023.09.18
      S23W77          

location: S24W71

13440 2023.09.17
2023.09.18
1 4 2 N18W58 0020 HRX AXX location: N17W58
13438 2023.09.18       N12W88          

location: N11W86

13442 2023.09.18
2023.09.20
      S09W55        

location: S09W53

13444 2023.09.19
2023.09.21
  2   N22W55 0002   BXO location: N23W47
13446 2023.09.21
2023.09.22
  4 2 N23W22 0009   BXO

location: N23W13

13445 2023.09.21
2023.09.22
9 8 6 S14W49 0140 DAO DAO

location: S14W51

area: 0180

13447 2023.09.24
2023.09.25
7 11 7 S22W31 0120 CSI DSO

area: 0210

location: S22W32

13448 2023.09.24
2023.09.25
2 12 3 N13E33 0110 HSX CSO area: 0230

location: N13E34

S8991 2023.09.24       N23W16          
S8993 2023.09.25   3 1 N14E23 0005   BXO  
S8994 2023.09.25   4   S20E40 0005   BXO  
13449 2023.09.26 9     N15E16 0090 DAO       SWPC includes both AR S8993 and S8996 in this region
S8995 2023.09.26       N05W27            
S8996 2023.09.26   15 13 N16E15 0210   DAO  
S8997 2023.09.26   1   S14E10 0001   AXX  
13450 2023.09.27
2023.09.27
8 17 10 S19E58 0070 DAI DAI area: 0180
S8999 2023.09.28   3   N23E13 0005   BXO    
S9000 2023.09.28   2   S20W08 0002   AXX    
S9001 2023.09.28   1   S28E09 0002   AXX  

 

Total spot count: 39 92 47  
Sunspot number: 109 242 137  (total spot count + 10 * number of spotted regions)
Weighted SN: 72 122 77  (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): 120 133 110  

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 (SC24 peak) 110.5 10.70
2014.04 143.9 144.8 112.5 116.4 (SC24 solar max) 7.88
2017.09 91.3 92.3 43.6 18.2 (-1.3) 18.22
(SC24 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
2022.02 109.1 106.5 60.9 64.7 (+4.6) 10.46
2022.03 117.0 115.8 78.6 68.7 (+4.0) 10.20
2022.04 130.8 131.7 84.0 73.0 (+4.3) 11.79
2022.05 133.8 136.8 96.5 77.4 (+4.4) 7.48
2022.06 116.1 119.8 70.3 81.1 (+3.7) 8.20
2022.07 125.4 129.5 91.4 86.7 (+5.6) 9.51
2022.08 114.2 117.1 74.6 92.6 (+5.9) 10.92
2022.09 135.1 136.5 96.0 96.5 (+3.9) 12.18
2022.10 133.5 132.7 95.5 98.9 (+2.4) 11.16
2022.11 123.4 120.7 80.5 101.1 (+2.2) 9.33
2022.12 147.9 143.4 112.8 106.7 (+5.6) 10.99
2023.01 182.4 176.6 144.4 113.4 (+6.7) 8.73
2023.02 167.2 163.2 111.3 117.9 (+3.5) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 123.3 (121.0 projected, +3.1) 14.42
2023.04 145.4 146.4 96.4 (126.3 projected, +5.3) 13.40
2023.05 155.6 159.2 137.9 (131.9 projected, +5.6) 10.67
2023.06 161.7 166.8 163.4 (135.1 projected, +3.2) 8.95
2023.07  176.4 182.2 159.1 (135.5 projected, +0.4) 8.15
2023.08  153.7 157.6 114.9 (137.3 projected, +1.8) 7.19
2023.09  154.2 (1)   122.7 (2A) / 131.4 (2B) / 140.9 (2C) (140.7 projected, +3.4) (14.7)
2023.10       (142.5 projected, +1.8)  
2023.11       (145.1 projected max SC25, +2.6)  
2023.12       (144.2 projected, -0.9)  
2024.01       (141.4 projected, -2.8)  
2024.02       (141.2 projected, -0.2)  
2024.03       (140.8 projected, -0.4)  

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: WDC-SILSO, Royal Observatory Of Belgium, Brussels

Solar cycles 24-25

Smoothed SF and sunspot numbers

Update on the progress of solar cycle 25 as of August 20, 2023

Looking back 6 months, the 365d smoothed values for solar flux and all sunspot numbers with the exception of NOAA's, are all above their solar cycle 24 peak. The first peak of solar cycle 25 is forecast to be between July 7 and 10, 2023 (solar flux on July 7, ISN and STAR 1K and 2K all have that peak on July 9, while NOAA peaks on July 10). This is unlikely to be the final peak of SC25, however, there is a small probability that it is the actual sunspot and solar flux maximum.

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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.