Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 28, 2023 at 16:55 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 active on September 27 under the influence of CME effects. Solar wind speed at SOHO ranged between 410 and 598 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 156.0 - increasing 16.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 154.88. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.4). Three hour interval K indices: 43333321 (planetary), 33343321 (Boulder), 53233333(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 14 active regions using 2K resolution (SN: 259) and in 12 active regions using 1K resolution (SN: 183) SDO/HMI images.

Region 13435 [N09W63] decayed further and lost all penumbra on negative polarity spots. C1 flares: C1.7 @ 08:07, C1.8 @ 15:31, C1.7 @ 16:16 UT
Region 13440 [N18W44] decayed slowly and quietly.
Region 13442 [S09W40] decayed slowly and quietly.
Region 13444 [N25W34] was quiet and stable.
Region 13445 [S14W38] decayed further and was quiet.
Region 13446 [N23W03] reemerged with tiny spots.
Region 13447 [S22W18] decayed slowly and quietly.
Region 13448 [N13E47] was quiet and stable.
New region 13450 [S17E69] rotated into view. The region produced an M1.1 flare at 09:07 UT on September 28. C1 flares: C1.3 @ 01:26, C1.3 @ 11:34, C1.5 @ 12:59, C1.4 @ 23:10 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8991 [N22E07] reemerged with tiny spots.
S8993 [N14E36] was quiet and stable.
S8994 [S20E55] decayed slowly and quietly.
S8996 [N15E28] developed further, has polarity intermixing and could produce an M class flare. C1 flares: C1.6 @ 00:41, C1.6 @ 03:56 UT
S8997 [S12E29] lost the trailing spot and gained tiny leading polarity spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.0 02:26   S8996 GOES16  
C2.0 04:55   S8996 GOES18  
C4.6 05:46   13450 GOES18  
C2.2 06:59   S8996 GOES18  
C2.6 09:47 N16E38 S8996 GOES16  
C2.1 10:12   13443 GOES16  
C2.0 15:22   13443 GOES16 attributed to simultaneous flare in AR 13450 by SWPC
C3.5 18:32 N14E34 S8996 GOES16  

Coronal mass ejections (CMEs)

September 25-27: 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 28-30.

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
7 10 6 N10W65 0190 DSO CSO

area: 0230

location: N09W63

13439 2023.09.17
2023.09.18
      S23W63          

location: S24W58

13440 2023.09.17
2023.09.18
1 5 2 N18W47 0030 HSX HRX location: N18W44
13438 2023.09.18       N12W74        

location: N11W73

13442 2023.09.18
2023.09.20
1 2 1 S09W41 0005 AXX AXX

location: S09W40

13444 2023.09.19
2023.09.21
  2 1 N22W41 0005   BXO location: N25W34
13446 2023.09.21
2023.09.22
  2 1 N23W08 0007   BXO  

location: N23W03

13445 2023.09.21
2023.09.22
22 28 15 S13W37 0200 DAI DSI

location: S14W38

area: 0230

S8988 2023.09.23       N19W53            
13447 2023.09.24
2023.09.25
14 20 14 S22W19 0180 DAO DAO

area: 0290

location: S22W18

13448 2023.09.24
2023.09.25
1 7 3 N13E45 0130 HSX HAX area: 0210

location: N13E47

S8991 2023.09.24   3 1 N23W03 0007   AXX    
S8993 2023.09.25   6 4 N14E36 0020   CRO  
S8994 2023.09.25   3   S20E55 0004   BXO  
13449 2023.09.26 10     N15E33 0070 CAO       SWPC includes both AR S8993 and S8996
S8995 2023.09.26       N05W14          
S8996 2023.09.26   20 11 N15E38 0180   DAI beta-gamma
S8997 2023.09.26   3   S10E39 0005   AXX  
13450 2023.09.27
2023.09.27
2 8 4 S18E66 0030 CRO DAO   was AR S8998

area: 0080

Total spot count: 58 119 63  
Sunspot number: 138 259 183  (total spot count + 10 * number of spotted regions)
Weighted SN: 91 155 99  (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): 152 143 146  

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  154.4 (1)   119.0 (2A) / 132.3 (2B) / 141.1 (2C) (140.7 projected, +3.4) (15.0)
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.