Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 28, 2023 at 08:00 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 (October 8, 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 27 under the influence of a high speed stream associated with CH1181. Solar wind speed at SOHO ranged between 340 and 486 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 127.5 - decreasing 31.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 155.73. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.0). Three hour interval K indices: 34321111 (planetary), 23232211 (Boulder), 54332232 (Andenes).

The background x-ray flux is at the class B5 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 11 active regions using 2K resolution (SN: 162) and in 8 active regions using 1K resolution (SN: 107) SDO/HMI images.

Region 13468 [S09W77] decayed slowly and quietly.
Region 13471 [S23W43] decayed and was mostly quiet.
Region 13472 [N21E29] was mostly quiet and stable. C1 flares: C1.1 @ 09:48 UT
Region 13473 [N17E58] was mostly quiet and stable. C1 flares: C1.3 @ ~15:40 UT (time and magnitude estimated due to GOES data gap)
New region 13474 [S17E38] emerged on October 26 and was numbered the next day by SWPC.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9082 [N18E18] was mostly quiet and stable. C1 flares: C1.2 @ 10:48 UT
S9093 [N13W38] was quiet and stable.
S9095 [N17W05] was quiet and stable.
New region S9096 [S12W23] emerged with a tiny spot before noon, then decayed slowly.
New region S9097 [S16E47] emerged with tiny spots.
New region S9098 [S24E03] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.1 08:54   S9089 GOES16 attributed to AR 13473 by SWPC

Coronal mass ejections (CMEs)

October 25-26: No obviously Earth directed CMEs were observed.
October 27: A CME was observed after a filament eruption near the northeast limb and flare in AR 13473 late on October 26. Post flare loops were observed over AR 13473. This event was the likely trigger of a filament eruption in an area between AR 13473 and AR 13472 as well as a flare in AR S9082. The latter events may be the source of CME components that were visible even over the west limbs in the early hours of the day.

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 poorly defined northern hemisphere positive polarity coronal hole (CH1181) was Earth facing on October 22. A large and well defined positive polarity trans equatorial coronal hole (CH1182) will rotate across the central meridian on October 27-28.

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 expected to be quiet to active on October 28 due to coronal high speed stream effects. Quiet conditions are likely on October 29. Quiet to minor storm conditions are possible on October 30-31 due to effects from CH1182 and potential interaction with the October 26-27 CME.

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
13468 2023.10.15
2023.10.16
1 2 1 S09W80 0010 AXX HRX

location: S09W77

13470 2023.10.16
2023.10.21
      N23W67        

location: N27W55

S9074 2023.10.20       S04W57            
13471 2023.10.22
2023.10.22
5 8 6 S23W46 0020 CRO BXO

location: S23W43

area: 0060

S9080 2023.10.22       N21W34            
S9081 2023.10.22       S17W30            
S9082 2023.10.22   7 2 N18E18 0020   BXO  
S9084 2023.10.23       N12W30            
S9085 2023.10.23       N10W02            
S9086 2023.10.24       S18W56          
S9087 2023.10.25       N19E41            
13472 2023.10.25
2023.10.26
3 10 5 N19E29 0010 CRO DRO location: N21E29

area: 0030

S9089 2023.10.25       N11E45          
13473 2023.10.25
2023.10.26
4 9 5 N16E57 0010 BXO BXO area: 0025

location: N17E58

S9091 2023.10.25       S16W11            
S9092 2023.10.25       S24W23            
S9093 2023.10.25   2 2 N13W38 0010   BXO  
13474 2023.10.26

2023.10.27

3 8 5 S17E37 0010 BXO CRO area: 0020

location: S17E38

S9095 2023.10.26   1   N17W05 0002   AXX  
S9096 2023.10.27   1   S12W23 0004   AXX    
S9097 2023.10.27   2 1 S16E47 0006   BXO    
S9098 2023.10.27   2   S17E38 0003   BXO    
Total spot count: 16 52 27  
Sunspot number: 66 162 107  (total spot count + 10 * number of spotted regions)
Weighted SN: 22 61 36  (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): 73 89 86  

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 97.6 (126.6 projected, +5.4) 13.40
2023.05 155.6 159.2 137.4 (132.2 projected, +5.6) 10.67
2023.06 161.7 166.8 160.5 (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) 14.26
2023.10  143.5 (1)   85.0 (2A) / 97.6 (2B) / 118.5 (2C) (142.8 projected, +1.8) (7.3)
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.