Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 17, 2023 at 09:50 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 16. Solar wind speed at SOHO ranged between 369 and 465 km/sec. The high latitude magnetometer at Andenes recorded quiet to major storm levels. A weak solar wind disturbance was observed arriving at DSCOVR at 01:55 UT on September 17, likely the September 14 CME.

Solar flux density measured at 20h UT on 2.8 GHz was 140.4 - decreasing 5.9 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 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.0). Three hour interval K indices: 10110233 (planetary), 10112322 (Boulder), 20011364 (Andenes).

The background x-ray flux is at the class B9 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 14 active regions using 2K resolution (SN: 210) and in 9 active regions using 1K resolution (SN: 124) SDO/HMI images.

Region 13423 [N18W84] rotated mostly out of view with only a couple of trailing spots visible by the end of the day. C1 flares: C1.6 @ 11:26 UT
Region 13425 [N24W59] decayed quickly and was quiet.
Region 13429 [N11W22] decayed substantially after the 2 M flares early in the day. C1 flares: C1.4 @ 03:31, C1.4 @ 04:13, C1.7 @ 07:52, C1.6 @ 11:47, C1.6 @ 13:05, C1.9 @ 13:19, C1.5 @ 13:58, C1.7 @ 15:10, C1.1 @ 23:22 UT
Region 13430 [S17W73] decayed slowly and quietly.
Region 13433 [N28E11] was quiet and stable.
Region 13434 [N08W13] decayed slowly and quietly.
New region 13435 [N10E80] rotated into view and produced a few C flares. The leader spot could be a separate region. C1 flares: C1.6 @ 16:20, C1.4 @ 18:46 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8960 [S13W27] decayed slowly and quietly.
S8961 [S13W23] reemerged with a tiny spot.
S8964 [N23W52] developed slowly and quietly.
S8965 [S19W35] decayed slowly and quietly.
S8966 [S07E64] decayed slowly and quietly.
New region S8968 [N15E10] was observed with tiny spots in an old plage area.
New region S8969 [N14W56] emerged with a tiny spot.

An unusually large filament eruption began just after 04h and peaked after 08h UT. The filament extended from north of AR 13433 to the west of AR 13429, and then southwards to just north of AR 13431. Early LASCO C2 imagery has a CME appearing first over the west limb at 09:12 UT and was soon afterwards observed as an asymmetrical full halo CME.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
M2.9/1N 00:50 N11W09 13429 GOES16  
C5.0 05:24   13435 GOES18  
M3.4/1B 05:38 N11W11 13429 GOES18  
C2.1 07:11 N12W10 13429 GOES16  
C2.2 07:29   13429 GOES16  
C2.6 07:40   13429 GOES16  
C2.1 12:05   13429 GOES16  
C2.8 13:25   13429 GOES16  
C2.5 15:51   13435 GOES16  
C3.7 15:57   13429 GOES16  

Coronal mass ejections (CMEs)

September 14: A long duration M1.2 (estimated) event started at 06:39 to the northeast of AR 13423 and peaked near 07:45 UT. LASCO C2 imagery displays the leading edge of a CME off the northwest limb at 07:24 UT. This CME later expanded to become a full halo CME. The CME likely arrived at Earth early on September 17.
September 15: No obviously Earth directed CMEs were observed.
September 16: A CME was observed just after 09h UT due to an extensive filament eruption across the central meridian. The full halo CME will probably reach Earth on September 19.

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 negative polarity coronal hole (CH1172) was Earth facing on September 11-13. Several coronal hole formed after the extensive filament eruption on September 16. CH1173 is a positive polarity trans equatorial coronal hole and was Earth facing on September 16. Positive polarity coronal hole CH1174 formed in the northern hemisphere on September 16 and will rotate across the central meridian on September 16-17. A negative polarity trans equatorial coronal hole (CH1174) will likely become Earth facing on September 19.

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 to fair.

Forecast

The geomagnetic field is expected to be quiet to active on September 17 due to the September 14 CME, quiet on September 18 and then quiet to major storm on September 19-20 when the September 16 CME reaches Earth. Effects from CH1173 and CH1174 are possible on September 20 and could extend into September 21. On September 22 a high speed stream from CH1175 will likely arrive and cause quiet t6o active conditions.

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
13423 2023.09.03
2023.09.04
  2   N18W84 0006   AXX

 

13424 2023.09.05
2023.09.05
      N17W76          

location: N17W69

13425 2023.09.05
2023.09.06
6 6 2 N24W65 0030 CRO CRO

location: N24W59

area: 0015

S8934 2023.09.06       S22W48            
13427 2023.09.07
2023.09.09
      S27W68           location: S29W63
S8940 2023.09.08       S22W24            
13429 2023.09.09
2023.09.10
16 26 17 N11W22 0090 DAI DAI

beta-delta

area: 0170

13434 2023.09.09
2023.09.15
2 2 1 N08W14 0010 AXX BXO area: 0005
13431 2023.09.09
2023.09.10
      S08W23        

location: S10W17

S8945 2023.09.09       N27W39            
13430 2023.09.10
2023.09.10
1 4 1 S17W74 0030 HRX BXO

 

S8948 2023.09.10       N12W45          
13433 2023.09.10
2023.09.12
1 6 4 N28E10 0080 HSX CSO area: 0170

location: N28E11

S8954 2023.09.11       N15E02          
S8955 2023.09.11       N23W41            
S8956 2023.09.12       S10W49            
S8958 2023.09.12       S24W43            
S8960 2023.09.13   2   S13W27 0003   AXX  
S8961 2023.09.13   1 1 S13W23 0004   AXX    
S8962 2023.09.13       N08W56            
S8963 2023.09.13       N18W28            
S8964 2023.09.14   5 3 N23W52 0020   DRO  
S8965 2023.09.15   3   S19W35 0004   BXO  
S8966 2023.09.15   1   S07E64 0002   AXX  
13435 2023.09.16
2023.09.16
2 4 2 N10E69 0090 DSO DHO   this may be 2 separate ARs

area: 0410

location: N10E80

S8968 2023.09.16   7 3 N15E10 0014   AXX    
S8969 2023.09.16   1   N14W56 0001   AXX    
Total spot count: 28 70 34  
Sunspot number: 88 210 124  (total spot count + 10 * number of spotted regions)
Weighted SN: 49 96 60  (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): 97 115 99  

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  148.0 (1)   61.7 (2A) / 115.8 (2B) / 115.8 (2C) (140.7 projected, +3.4) (11.9)
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.