Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 12, 2023 at 06:35 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 on September 11. Solar wind speed at SOHO ranged between 336 and 442 km/sec, probably under the influence of a low speed stream from CH1170. The high latitude magnetometer at Andenes recorded quiet to unsettled levels.

Solar flux density measured at 20h UT on 2.8 GHz was 176.4 - increasing 18.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 154.05. 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: 12111112 (planetary), 22113222 (Boulder), 21022123 (Andenes).

The background x-ray flux is at the class C2 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 319) and in 13 active regions using 1K resolution (SN: 215) SDO/HMI images.

Region 13423 [N15W28] decayed in the leading spot section and was otherwise mostly unchanged. M class flaring is possible. C1 flares: C1.9 @ 13:17 UT
Region 13425 [N23E02] developed in the trailing spot section and gained a magnetic delta structure. M class flaring is possible. C1 flares: C1.7 @ 13:57 UT
Region 13427 [S28E02] decayed slowly and quietly.
Region 13428 [N14W63] decayed slowly and quietly.
Region 13429 [N11E46] gained spots, however none of the spots have mature penumbra. The region has polarity intermixing and produced the largest flare of the day.
Region 13430 [S17W03] developed slowly and quietly.
Region 13431 [S07E47] decayed after producing many flares, including 2 M flares. The magnetic delta disappeared.
New region 13432 [S22W73] emerged on September 8 and was numbered by SWPC 3 days later as the region approached the southwest limb.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8935 [N30W18] reemerged with tiny spots.
S8940 [S22E41] was quiet and stable.
S8942 [N07E53] was quiet and stable.
S8949 [N09E32] decayed slowly and quietly.
S8950 [N28E77] rotated fully into view with a mature spot.
New region S8952 [S16W24] emerged before noon, then decayed slowly.
New region S8954 [N17E57] emerged with tiny spots.
New region S8955 [N31E28] was observed with tiny spots in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C3.6 00:40   13421 GOES16  
M1.3/1F 01:28 N08E62 13429 GOES16 CME, moderate type II radio sweep
C2.1 03:42   13431 GOES16 simultaneous flare in AR 13425
M1.1 04:07 S09E59 13431 GOES16  
C2.6 04:36   13431 GOES18  
C7.2 05:42   13431 GOES18  
C4.5 05:48   13421 GOES16  
C9.3/1N 06:01 S04E55 13431 GOES16  
C6.8 06:17   13431 GOES16  
C3.5 06:56   13431 GOES16  
C2.1 07:30   13431 GOES16  
C2.7 10:12   13423 GOES16  
C7.4 10:37   13431 GOES16  
C4.0 11:03   13423 GOES16  
C3.7/1F 11:27 S04E53 13431 GOES16  
C2.3 12:17   13425 GOES16 simultaneous flares in AR 13429 and 13431
M1.1 14:49 S04E50 13431 GOES16  
C2.4 17:07   13423 GOES16  
C5.5 17:35 N21E09 13425 GOES16 simultaneous flare in AR 13431
C2.5 18:25   13425 GOES16  
C2.9 18:35   13423 GOES16  
C3.3 18:49   13425 GOES16 simultaneous flare in AR 13421
C3.4 19:50   13421 GOES16 simultaneous flare in AR 13425
C8.2 21:14   13425 GOES16  
C2.3 23:23   13431 GOES16  

Coronal mass ejections (CMEs)

September 9-11: 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]

Northern hemisphere positive polarity coronal holes (CH1169 and CH1170) rotated across the central meridian on September 8-10. A negative polarity coronal hole (CH1171) in the southern hemisphere was Earth facing on September 9-10. A trans equatorial negative polarity coronal hole (CH1172) will be Earth facing on September 11-13.

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 to good. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to active on September 12-15 due to effects from CH1169, CH1171 and CH1172.

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
13418 2023.08.29
2023.08.30
1     N20W93 0020 HRX     rotated out of view
13421 2023.09.02
2023.09.03
4     N15W91 0010 BXO    

rotated out of view

13422 2023.09.03
2023.09.04
      N14W75          

location: N11W71

13423 2023.09.03
2023.09.04
21 39 19 N16W30 0420 EKC EKI

area: 0610

location: N15W28

S8921 2023.09.03       S14W35            
13424 2023.09.05
2023.09.05
      N17W06        

location: N18W00

S8926 2023.09.05       N23W54            
13425 2023.09.05
2023.09.06
24 43 21 N23E02 0100 EAI DAI beta-gamma-delta

area: 0230

location: N23E15

S8928 2023.09.05       S22W33            
S8931 2023.09.06       N09W51            
S8933 2023.09.06       S18W57            
S8934 2023.09.06       S22E17            
13426 2023.09.07
2023.09.07
      S14W42         location: S17W37
S8935 2023.09.07   2 1 N30W18 0004   AXX    
13427 2023.09.07
2023.09.09
3 8 3 S27E02 0010 BXO CRO location: S28E02

area: 0020

S8937 2023.09.07       N11W16            
13432 2023.09.08
2023.09.11
3 6 3 S24W74 0010 BXO CRO location: S22W73

area: 0020

S8940 2023.09.08   2   S22E41 0003   BXO  
13429 2023.09.09
2023.09.10
4 13 10 N10E46 0030 DRO DRI beta-gamma

area: 0060

location: N11E46

S8942 2023.09.09   1 1 N07E53 0050   HSX  
13428 2023.09.09
2023.09.10
1 3 2 N14W62 0005 AXX AXX  
13431 2023.09.09
2023.09.10
5 12 8 S07E47 0050 DAO DAI beta-gamma

area: 0130

S8945 2023.09.09       N27E26            
13430 2023.09.10
2023.09.10
7 22 14 S16W05 0030 CRO DRI

area: 0120

location: S17W03

S8948 2023.09.10       N08E24          
S8949 2023.09.10   2   N09E32 0004   AXX  
S8950 2023.09.10   1 1 N28E77 0170   HSX  
S8952 2023.09.11   1 1 S16W24 0002   AXX    
S8954 2023.09.11   2 1 N17E57 0005   BXO    
S8955 2023.09.11   2   N31E28 0004   AXX    
Total spot count: 73 159 85  
Sunspot number: 173 319 215  (total spot count + 10 * number of spotted regions)
Weighted SN: 102 201 127  (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): 190 175 172  

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  149.7 (1)   43.6 (2A) / 118.9 (2B) / 120.7 (2C) (140.7 projected, +3.4) (11.0)
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.