Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 27, 2023 at 06:25 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 minor storm on October 26 under the influence of a high speed stream associated with CH1181. Solar wind speed at SOHO ranged between 344 and 555 km/sec. The high latitude magnetometer at Andenes recorded quiet to major storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 126.4 - decreasing 28.1 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 21 (STAR Ap - based on the mean of three hour interval ap indices: 21.0). Three hour interval K indices: 33244345 (planetary), 23244444 (Boulder), 43134466 (Andenes).

The background x-ray flux is at the class B6 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 10 active regions using 2K resolution (SN: 166) and in 8 active regions using 1K resolution (SN: 108) SDO/HMI images.

Region 13468 [S09W62] was quiet and stable.
Region 13470 [N27W42] was quiet and stable.
Region 13471 [S23W31] decayed slightly and was mostly stable. C1 flares: C1.0 @ 01:49, C1.9 @ 17:00, C1.6 @ 18:39 UT
New region 13472 [N19E43] emerged on October 25 and was numbered the next day by SWPC. C1 flare: C1.4 @ 04:08 UT
New region 13473 [N17E69] rotated in to view on October 25 with SWPC numbering the region the following day. The region was unstable and produced a very long duration M1.4 flare during the last hour of the day. C1 flares: C1.1 @ 03:53, C1.7 @ 12:23, C1.2 @ 19:28 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9082 [N18E28] reemerged with many tiny spots and was unstable. C1 flares: C1.7 @ 04:44, C1.5 @ 22:03 UT. Another flare was observed at 23:05 UT, however, it was dwarfed by the much larger event in AR 13473.
S9089 [N11E58] decayed slowly and was mostly quiet. C1 flares: C1.3 @ 12:41, C1.4 @ 19:58 UT
S9093 [N13W23] developed slowly and quietly.
New region S9094 [S17E52] emerged with tiny spots.
New region S9095 [N12E08] emerged within the boundaries of CH1182 and could cause the coronal hole to diminish in size if there is further development.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.2 13:26 S20W38 S9086 GOES16  
C2.4 16:39 S22W27 13471 GOES16  
M1.4 23:24   13473 GOES16 LDE, moderate type II radio sweep, CME

Coronal mass ejections (CMEs)

October 24-25: No obviously Earth directed CMEs were observed.
October 26-27: At least a partial halo CME was observed after the M1.4 LDE in AR 13473 late on October 26. Faint slow moving CME components could be observed off the west limb too a few hours after the flare. The flare triggered a filament eruption west of AR 13473 and a small flare in AR S9082.

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 27 due to effects from CH1181. Quiet conditions are likely on October 28-29. Quiet to major storm conditions are expected on October 30-31 due to CME effects and effects from CH1182.

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 S09W66 0020 HRX CRO

location: S09W62

13470 2023.10.16
2023.10.21
  3   N23W53 0008   BXO

location: N27W42

S9074 2023.10.20       S04W44            
S9078 2023.10.22       S15W59            
13471 2023.10.22
2023.10.22
9 20 11 S23W33 0030 DRO DRI

location: S23W31

area: 0060

S9080 2023.10.22       N21W21            
S9081 2023.10.22       S17W17            
S9082 2023.10.22   14 3 N13E27 0030   BXO    
S9084 2023.10.23       N12W17            
S9085 2023.10.23       N10E11            
S9086 2023.10.24       S18W43          
S9087 2023.10.25       N19E54          
13472 2023.10.25
2023.10.26
6 9 4 N20E43 0030 CRO CRO location: N19E43
S9089 2023.10.25   1 1 N11E58 0003   AXX  
13473 2023.10.25
2023.10.26
1 6 2 N13E62 0010 BXO BXO area: 0015

location: N17E69

S9091 2023.10.25       S16E02          
S9092 2023.10.25       S24W10          
S9093 2023.10.25   4 1 N13W23 0010   BXO  
S9094 2023.10.26   6 5 S17E52 0020   CRO    
S9095 2023.10.26   1   N12E08 0003   AXX    
Total spot count: 17 66 28  
Sunspot number: 57 166 108  (total spot count + 10 * number of spotted regions)
Weighted SN: 26 78 37  (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): 63 91 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  144.1 (1)   82.8 (2A) / 98.8 (2B) / 120.5 (2C) (142.8 projected, +1.8) (7.2)
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.