Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 18, 2023 at 08:30 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 minor storm on December 17 under the influence of CME effects. Solar wind speed at SOHO ranged between 440 and 553 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 154.6 - decreasing 1.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.87. 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 33 (STAR Ap - based on the mean of three hour interval ap indices: 32.9). Three hour interval K indices: 45455523 (planetary), 34455633 (Boulder), 45645433 (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: 287) and in 16 active regions using 1K resolution (SN: 224) SDO/HMI images.

Region 13516 [S17W39] was quiet and stable.
Region 13518 [N14E09] was quiet and stable.
Region 13519 [S11W17] decayed slowly and was mostly quiet.
Region 13520 [N10W83] rotated mostly out of view. C1 flares: C1.8 @ 13:38 UT
Region 13521 [N11E46] was quiet and stable.
Region 13522 [S04E12] was quiet and stable.
Region 13523 [N22E51] decayed slowly and quietly.
Region 13524 [N27E49] was quiet and stable.
Region 13525 [S09E31] was quiet and stable.
New region 13526 [N14E70] rotated into view on December 16 and was numbered the next day by SWPC as the region developed slowly.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9244 [N09E28] developed slowly and quietly.
S9245 [S19E66] developed slowly and quietly.
New region S9246 [S03W42] emerged with tiny spots.
New region S9247 [N14E55] emerged with a tiny spot.
New region S9248 [S21E45] was observed with tiny spots in an old plage area.
New region S9249 [N21W19] was observed with a tiny spot in an old plage area.

AR 13517 produced a C1.7 flare at 04:45 UT
AR 13514 was the source of several C1 flares: C1.5 @ 02:18, C1.6 @ 02:41, C1.6 @ 03:04, C1.4 @ 04:20, C1.5 @ 05:14, C1.8 @ 11:30, C1.7 @ 14:05 UT

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.0 06:17   13514 GOES16  
C2.5 06:35   13517 GOES16  
C4.1 06:46   13514 GOES16  
C2.4 07:52   13514 GOES16  
C2.6 08:10   13514 GOES16  
C2.2 08:32   13514 GOES16  
C2.9 09:01   13514 GOES16  
C2.1 10:25   13514 GOES16  
C2.0 12:17   13520 GOES16  
C2.5 13:05   13520 GOES16  
C3.3 17:29   13524 GOES16  
C3.5 18:14   13514 GOES16  
C3.5 18:21   13514 GOES16  
C2.5 19:00   13524 GOES16  
M1.1 20:17   13514 GOES16  
C2.1 21:17   S9244 GOES16  
C4.8 21:32   13526 GOES16  

Coronal mass ejections (CMEs)

December 15: A partial halo CME was observed after the M6 flares AR 13514. The CME could reach Earth on December 18 and cause unsettled and active intervals.
December 16-17: 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 major storm on December 18 due to CME effects and effects from CH1193. Quiet to minor storm is likely on December 19 becoming quiet to active on December 20.

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
13514 2023.12.05
2023.12.06
4     N05W94 0120 DAC     rotated out of view
13516 2023.12.08
2023.12.08
2 5 2 S18W40 0010 AXX BXO

location: S17W39

13515 2023.12.08
2023.12.08
      S14W44            
13517 2023.12.08
2023.12.11
      N11W83         location: N14W80
13518 2023.12.12
2023.12.12
  12 4 N13E07 0025   BXO

location: N14E09

S9232 2023.12.12       S19W53            
13519 2023.12.12
2023.12.13
18 27 16 S11W16 0130 DSI DSI location: S11W17

area: 0160

13520 2023.12.13
2023.12.13
3 2 1 N10W86 0040 CSO BXO

 

13521 2023.12.14
2023.12.15
3 12 6 N12E44 0030 HAX CRO area: 0060

location: N11E46

S9238 2023.12.14       N30W01          
13523 2023.12.15
2023.12.16
1 5 2 N21E50 0010 HRX BXO area: 0020

location: N22E51

13525 2023.12.15
2023.12.16
3 13 6 S09E31 0020 CRO CRO

 

13522 2023.12.15
2023.12.16
  7 4 S03E12 0010   BXO location: S04E12
13524 2023.12.15
2023.12.16
2 4 2 N26E49 0020 HRX HRX location: N27E49

area: 0040

13526 2023.12.16
2023.12.17
3 7 4 N15E69 0020 CAO BXO area: 0040

location: N14E70

S9244 2023.12.16   12 5 N09E28 0040   BXO  
S9245 2023.12.16   8 4 S19E66 0030   DRO  
S9246 2023.12.17   9 5 S03W42 0040   DRO    
S9247 2023.12.17   1 1 N14E55 0004   AXX    
S9248 2023.12.17   2 1 S21E45 0005   BXO    
S9249 2023.12.17   1 1 N21W19 0003   AXX    
Total spot count: 39 127 64  
Sunspot number: 129 287 224  (total spot count + 10 * number of spotted regions)
Weighted SN: 73 147 84  (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): 142 158 179  

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
2023.12 139.0 (1)   65.5 (2A) / 119.5 (2B) / 144.4(2C) (132.7 projected, -1.4) (10.9)
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.