Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 20, 2023 at 08:35 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 active on December 19 under the influence of effects from CH1193. Solar wind speed at SOHO ranged between 618 and 755 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 179.3 - decreasing 10.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.96. 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 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.1). Three hour interval K indices: 43221223 (planetary), 34212222 (Boulder), 55322225 (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: 364) and in 14 active regions using 1K resolution (SN: 248) SDO/HMI images.

Region 13518 [N14W18] was quiet and stable.
Region 13519 [S10W44] has minor polarity intermixing and could produce C flares.
Region 13521 [N12E19] developed during the latter half of the day, C flares are likely.
Region 13522 [S02W13] decayed slowly and quietly.
Region 13524 [N26E28] was mostly quiet and was merged with AR 13523. C1 flares: C1.9 @ 21:36 UT
Region 13525 [S08E05] decayed slowly and quietly.
Region 13526 [N14E45] developed slowly and was mostly quiet.
Region 13527 [S01W72] decayed slowly and quietly.
Region 13528 [N08E01] developed slowly and appears to be maturing. The region was the most active on the visible disk.
Region 13529 [S20E39] developed further and could produce M class flares.
New region 13530 [N08E65] rotated into view on December 18 with SWPC numbering the region the next day.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9251 [S13W18] was quiet and stable.
New region S9252 [S19E14] was observed with tiny spots in an old plage area.
New region S9253 [N21E40] emerged with tiny spots.
New region S9254 [S20E82] rotated into view with a large mature spot.
New region S9255 [N14E82] rotated into view with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.6/1N 02:52 N05E11 13528 GOES16  
C7.3 03:04   13528 GOES16  
C3.7 06:38 N05E09 13528 GOES16  
C2.5 07:58   13529 GOES16  
C2.3 10:52   13528 GOES16  
C3.0 12:22 behind northwest limb   GOES16 LDE
C7.1 15:39   13529 GOES16  
C2.7 17:39   13529 GOES16  
C2.5 17:53   13524 GOES16  
C2.2 20:08   13526 GOES16  
C2.9 23:42   13521 GOES16  

Coronal mass ejections (CMEs)

December 17-19: 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. A negative polarity southern hemisphere coronal hole (CH1194) was Earth facing on December 18-19, but is likely too far to the south to cause a geomagnetic disturbance.

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 December 20 due to effects from CH1193. Quiet conditions are likely on December 21. There's a slight chance of unsettled intervals on December 21-22 due to possible effects from CH1194.

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
      S18W68        

location: S17W65

13515 2023.12.08
2023.12.08
      S14W73            
13518 2023.12.12
2023.12.12
  7   N13W21 0010   BXO

location: N14W18

13519 2023.12.12
2023.12.13
9 31 17 S10W42 0090 DSO DSI

location: S10W44

area: 0120

13521 2023.12.14
2023.12.15
3 19 14 N12E19 0020 CRO DRI area: 0120
S9238 2023.12.14       N30W27          
13523 2023.12.15
2023.12.16
1     N25E24 0005 AXX     merged with AR 13524

location: N23E26

13525 2023.12.15
2023.12.16
1 9 2 S05E03 0005 AXX BXO

area: 0015

location: S08E05

13522 2023.12.15
2023.12.16
  1 1 S03W17 0003   AXX location: S02W13
13524 2023.12.15
2023.12.16
1 21 8 N26E22 0005 AXX CRI location: N26E28

area: 0040

13526 2023.12.16
2023.12.17
5 22 12 N15E44 0190 CAO CAI

location: N14E45

13528 2023.12.16
2023.12.18
10 26 18 N08E01 0110 DAO DAI area: 0270
13529 2023.12.16
2023.12.18
8 39 21 S19E42 0250 DKI DKI area: 0450

location: S20E39

13527 2023.12.17 2 4 3 S01W69 0025 CAO CAO area: 0050

location: S01W72

S9247 2023.12.17       N14E28          
S9248 2023.12.17       S21E19            
S9249 2023.12.17       N21W45            
13530 2023.12.18
2023.12.19
4 11 7 N09E63 0050 CAO EAO location: N09E65

area: 0110

S9251 2023.12.18   2 2 S13W18 0003   AXX  
S9252 2023.12.19   7 1 S19E14 0012   BXO    
S9253 2023.12.19   3 2 N21E40 0010   BXO    
S9254 2023.12.19   1 1 S20E82 0200   HAX    
S9255 2023.12.19   1   N14E82 0001   AXX    
Total spot count: 44 204 109  
Sunspot number: 144 364 249  (total spot count + 10 * number of spotted regions)
Weighted SN: 82 250 151  (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): 158 200 199  

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
2023.12 142.3 (1)   74.6 (2A) / 121.7 (2B) / 152.6 (2C) (132.7 projected, -1.4) (12.8)
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.