Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 2, 2023 at 06:45 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 (October 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (October 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 (October 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (October 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 October 1. Solar wind speed at SOHO ranged between 382 and 425 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels.

Solar flux density measured at 20h UT on 2.8 GHz was 161.1 - increasing 25.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 155.06. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.5). Three hour interval K indices: 42212022 (planetary), 32213222 (Boulder), 43122234 (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 12 active regions using 2K resolution (SN: 265) and in 12 active regions using 1K resolution (SN: 176) SDO/HMI images.

Region 13447 [S22W72] decayed slowly and quietly.
Region 13448 [N13W06] was quiet and stable.
Region 13450 [S19E18] has significant polarity intermixing and could produce M flares. C1 flares: C1.8 @ 07:46, C1.9 @ 21:15 UT
Region 13451 [N17E48] decayed and simplified as the magnetic delta structures disappeared. C1 flares: C1.6 @ 12:31, C1.6 @ 17:57 UT
New region 13452 [N10E47] developed gaining spots and area. The region became magnetically less complex. C and M class flares are possible. SWPC finally decided to split their AR 13451 into two regions. C1 flares: C1.7 @ 13:09 UT
New region 13453 [N11E10] emerged with several spots. C1 flares: C1.8 @ 08:45 UT
New region 13454 [S12E65] rotated into view on September 30 and was numbered the next day by SWPC.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8993 [N17W08] decayed slowly and was mostly quiet.
S8996 [N15W25] decayed slowly and was mostly quiet.
S9005 [N23E07] was quiet and stable.
New region S9013 [N30E20] emerged with tiny spots.
New region S9014 [N24E73] rotated into view with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.7 00:19   13452 GOES16  
C3.1 00:45   13452 GOES16  
C3.0 01:06   13450 GOES16  
M2.5 01:31   13452 GOES16  
M1.5 01:47   13451 GOES16  
C9.3 03:24   13445 GOES16  
C3.5 04:05   13452 GOES16  
C3.7 04:14   13445 GOES16  
C3.6 05:15   13450 GOES18  
C2.2 05:54   S9014 GOES16  
C2.0 07:04   13452 GOES16  
C2.5 09:15   S8993 GOES16  
C5.0 09:51   13451 GOES16  
C2.3 10:48   13453 GOES16  
C3.6 11:14   13451 GOES16  
C2.9 14:29   S9014 GOES16  
C3.4 14:48   13452 GOES16  
C2.3 19:19   13450 GOES16  
C2.1 20:15   13450 GOES16  
C2.5 22:43   13450 GOES16  
C4.5 23:11   S8993/S8996 GOES16  

Coronal mass ejections (CMEs)

September 29 - October 1: 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]

A coronal hole (CH1177) in the northern hemisphere was Earth facing on September 30.

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

Forecast

The geomagnetic field is likely to be quiet to unsettled on October 2 and quiet to active on October 3-4 due to effects from a positive polarity coronal hole.

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
13446 2023.09.21
2023.09.22
      N23W64          

location: N23W52

13447 2023.09.24
2023.09.25
1 1 1 S23W72 0070 HSX HSX

area: 0110

location: S22W72

13448 2023.09.24
2023.09.25
1 18 3 N13W06 0080 HSX HSX area: 0220
S8991 2023.09.24       N23W55            
S8993 2023.09.25   8 3 N17W18 0015   BXO  
S8994 2023.09.25       S21W07          
13449 2023.09.26 8     N15W22 0040 CSO       SWPC includes both AR S8993 and S8996 in this region
S8996 2023.09.26   2 1 N15W25 0050   HAX  
S8997 2023.09.26       S14W29            
13450 2023.09.27
2023.09.27
20 43 20 S19E18 0180 EAI EAI beta-gamma

area: 0360

S8999 2023.09.28       N23W26            
S9000 2023.09.28       S17W49            
S9001 2023.09.28       S28W30            
13451 2023.09.29
2023.09.30
7 19 8 N16E48 0050 DRI DRI area: 0070
13452 2023.09.29
2023.10.01
12 22 10 N11E47 0120 DAI DAI  
S9005 2023.09.30   5 1 N23E07 0015   CRO  
S9006 2023.09.30       S18W40          
S9007 2023.09.30       N07W23          
13454 2023.09.30
2023.10.01
1 5 2 S12E64 0015 HRX CRO  
S9009 2023.09.30       N15W44          
S9010 2023.09.30       N27W56          
S9011 2023.09.30       S36W32          
13453 2023.10.01
2023.10.01
6 17 5 N12E11 0020 CRO DRI   was AR S9012

area: 0080

location: N11E10

S9013 2023.10.01   3 1 N30E20 0010   CRO    
S9014 2023.10.01   2 1 N24E73 0010   AXX    
Total spot count: 56 145 56  
Sunspot number: 136 265 176  (total spot count + 10 * number of spotted regions)
Weighted SN: 90 185 96  (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): 150 146 141  

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
2022.03 117.0 115.8 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)
2023.03 157.2 155.6 123.3 121.2 (+3.3) 14.42
2023.04 145.4 146.4 96.4 (126.6 projected, +5.4) 13.40
2023.05 155.6 159.2 137.9 (132.2 projected, +5.6) 10.67
2023.06 161.7 166.8 163.4 (135.4 projected, +3.2) 8.95
2023.07  176.4 182.2 159.1 (135.8 projected, +0.4) 8.15
2023.08  153.7 157.6 114.9 (137.6 projected, +1.8) 7.19
2023.09  154.4 156.0 133.6 (141.0 projected, +3.4) 14.4
2023.10  161.1 (1)   4.4 (2A) / 136 (2B) / 143.9 (2C) (142.8 projected, +1.8) (7.5)
2023.11       (145.4 projected max SC25, +2.6)  
2023.12       (144.5 projected, -0.9)  
2024.01       (141.7 projected, -2.8)  
2024.02       (141.5 projected, -0.2)  
2024.03       (141.0 projected, -0.5)  
2024.04       (138.2 projected, -2.8)  

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: 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.