Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 19, 2023 at 08:40 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 (December 7, 2023)
Solar cycle Solar cycles 23-25 (December 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (December 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 (December 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (December 1, 2023) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (November 26, 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 major storm on December 18, first under the influence of CME effects and after 18h under the influence of a high speed stream from CH1193. Solar wind speed at SOHO ranged between 490 and 669 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 161.4 - decreasing 10.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.89. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.42 on June 4, 2023). The Potsdam WDC planetary A index was 26 (STAR Ap - based on the mean of three hour interval ap indices: 26.3). Three hour interval K indices: 24643335 (planetary), 23554333 (Boulder), 32443355 (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 16 active regions using 2K resolution (SN: 349) and in 14 active regions using 1K resolution (SN: 227) SDO/HMI images.

Region 13516 [S17W52] decayed slowly and quietly.
Region 13518 [N14W04] was quiet and stable.
Region 13519 [S11W30] gained spots as new flux emerged to the north of the main penumbrae, this caused weak polarity intermixing.
Region 13521 [N11E32] gained spots, lost area and was quiet
Region 13522 [S04W01] decayed slowly and quietly.
Region 13523 [N23E39] gained spots and was quiet.
Region 13524 [N27E38] gained trailing spots and was mostly quiet.
Region 13525 [S08E18] decayed slowly and quietly.
Region 13526 [N14E58] developed slowly and produced a few flares. C1 flares: C1.9 @ 02:00 UT
New region 13527 [S02W58] emerged on December 17 and was numbered by SWPC the next day as the region matured.
New region 13528 [N08E14] emerged on December 16 with SWPC numbering the region 2 days later. The region developed fairly quickly on December 18 and a minor M class flare is possible due to minor polarity intermixing.
New region 13529 [S19E51] rotated into view on December 16 and has developed slowly since then. SWPC numbered the region on Dec.18.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9238 [N28W18] reemerged with a tiny spot.
S9247 [N14E41] was quiet and stable.
New region S9250 [N09E79] rotated into view with several spots.
New region S9251 [S18W04] was observed with a tiny spot in an old plage area.

AR 13514 behind the northwest limb produced a C1.7 flare at 03:24 UT

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.2 00:26   13519 GOES16  
C2.1 01:28   13514 GOES16  
C6.0 02:55 N26E67 13524 GOES16  
C2.1 03:40   13519 GOES16  
C4.2 04:08   13526 GOES16  
C2.0 06:49   13526 GOES16  
C2.4 07:05   13514 GOES16  
C2.4 07:37   13514 GOES16  
C2.0 09:34   13519 GOES16 simultaneous flare in AR 13514
C3.1 10:29   13514 GOES16  
C3.6 10:39   13514 GOES16  
C2.6 11:08   13514 GOES16  
C2.3 12:09   13526 GOES16  
C2.3 12:36   13514 GOES16  
C2.5 13:08   13514 GOES16  
C2.4 13:56   13526 GOES16  
C6.5 14:22   13528 GOES16  
C4.4 15:21   13514 GOES16  
C2.7 16:54   13514 GOES16  
C2.1 17:54   13528 GOES16  
C2.3 18:04   13528 GOES16  
C2.3 19:09   13514 GOES16  
C4.5 19:25   13528 GOES16  
C4.0 20:36   13526 GOES16  
C2.9 21:03   13528 GOES16  

Coronal mass ejections (CMEs)

December 16-18: No obviously Earth directed CME 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 positive polarity northern hemisphere coronal hole (CH1193) was Earth facing on December 14-16.

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 minor storm on December 19 due to effects from CH1193. Quiet to unsettled is likely on December 20 becoming quiet on December 21. There's a slight chance of unsettled intervals on December 21-22 due to possible effects from CH1193. CH1193 may be too far to the south to cause a disturbance.

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
13516 2023.12.08
2023.12.08
  5   S18W54 0005   BXO

location: S17W52

13515 2023.12.08
2023.12.08
      S14W57            
13518 2023.12.12
2023.12.12
  8 3 N13W07 0015   BXO

location: N14W04

13519 2023.12.12
2023.12.13
11 37 16 S11W28 0130 DSI DSI beta-gamma

location: S11W30

13521 2023.12.14
2023.12.15
8 20 8 N11E36 0050 DAO BXO area: 0040

location: N11E32

S9238 2023.12.14   1   N30W14 0001   AXX    
13523 2023.12.15
2023.12.16
2 8 4 N22E38 0010 BXO BXO area: 0020

location: N23E39

13525 2023.12.15
2023.12.16
1 5 3 S09E17 0010 AXX CRO

 

13522 2023.12.15
2023.12.16
  4 2 S03W03 0008   BXO location: S04W01
13524 2023.12.15
2023.12.16
1 6 3 N27E36 0010 AXX CRO location: N27E38

area: 0020

13526 2023.12.16
2023.12.17
2 19 8 N15E57 0030 CAO CAI area: 0110

location: N14E58

13528 2023.12.16
2023.12.18
9 31 16 N09E12 0040 DSI DAI area: 0200

location: N08E14

13529 2023.12.16
2023.12.18
8 27 14 S20E56 0060 DSI DAI area: 0180

location: S19E51

13527 2023.12.17 5 5 3 S03W56 0040 CAO DSO area: 0120
S9247 2023.12.17   4 3 N14E41 0010   AXX  
S9248 2023.12.17       S21E32          
S9249 2023.12.17       N21W32          
S9250 2023.12.18   8 3 N09E79 0150   DAO    
S9251 2023.12.18   1 1 S18W04 0003   AXX    
Total spot count: 47 189 87  
Sunspot number: 137 349 227  (total spot count + 10 * number of spotted regions)
Weighted SN: 77 225 123  (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): 151 192 182  

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
2022.04 130.8 131.7 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 80.5 101.2 (+2.3) 9.33
2022.12 147.9 143.4 112.8 106.7 (+5.5) 10.99
2023.01 182.4 176.6 144.4 113.3 (+6.6) 8.73
2023.02 167.2 163.2 111.3 117.8 (+3.5) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 123.3 121.0 (+3.2) 14.42
2023.04 145.4 146.4 97.6 122.7 (+1.7) 13.40
2023.05 155.6 159.2 137.4 123.9 (+1.2) 10.67
2023.06 161.7 166.8 160.5 (126.3 projected, +2.4) 8.95
2023.07  176.4 182.2 159.1 (127.1 projected, +0.8) 8.15
2023.08  153.7 157.6 114.8 (128.2 projected, +1.1) 7.19
2023.09  154.4 156.0 133.6 (130.4 projected, +2.2) 14.26
2023.10  142.8 141.9 99.4 (132.2 projected, +1.8) 8.16
2023.11 153.5 150.2 105.4 (134.1 projected max SC25, +1.9) 12.20
2023.12 140.3 (1)   69.9 (2A) / 120.4 (2B) / 148.1 (2C) (132.7 projected, -1.4) (13.0)
2024.01       (130.0 projected, -2.7)  
2024.02       (129.9 projected, -0.1)  
2024.03       (129.3 projected, -0.6)  
2024.04       (130.1 projected, +0.8)  
2024.05       (132.2 projected, +2.1)  
2024.06       (131.5 projected, -0.7)  

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 December 7, 2023

Due to relatively low solar activity over the last couple of months, the possibility that solar cycle 25 has already peaked has increased significantly. Whether the first peak (and maybe solar max) will be in June or July depends on solar activity in December and early January 2024. If the average solar flux is less than 150 during this period, the first peak of solar cycle 25 using 365 day smoothing will likely be sometime between June 2 and July 9. Should the average solar flux instead become 140 then the peak date will be in early June (June 4 for solar flux, June 6 for STAR 2K SN, and June 7 for all the other sunspot numbers in the graph above). We won't know for a while yet when the final peak will be, however, it is interesting that the peak of SC25 could be as early as June 2023. The next update will likely be posted here in January 2024.

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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.