Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 22, 2023 at 09:35 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 unsettled on December 21. Solar wind speed at SOHO ranged between 310 and 455 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 193.6 - increasing 15.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.24. 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 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 31021100 (planetary), 21131211 (Boulder), 51010220 (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 15 active regions using 2K resolution (SN: 336) and in 14 active regions using 1K resolution (SN: 249) SDO/HMI images.

Region 13519 [S09W70] decayed slowly as it approached the southwest limb. The region was unstable and produced several C and M flares. C1 flares: C1.9 @ 01:00, C1.4 @ 13:17, C1.6 @ 14:44, C1.8 @ 20:10 UT
Region 13521 [N12W07] matured and was mostly quiet.
Region 13522 [S05W42] reemerged with tiny spots.
Region 13524 [N26E03] decayed slowly and was mostly quiet.
Region 13525 [S08W21] was quiet and stable.
Region 13526 [N14E18] has a weak magnetic delta structure in the northwestern part of the largest penumbra. A minor M class flare is possible.
Region 13528 [N08W26] decayed slowly and was mostly quiet. C1 flares: C1.9 @ 08:50 UT
Region 13529 [S19E14] has large spots, however, the region has a fairly simple magnetic layout. There is a small probability of a major flare.
Region 13530 [N08E37] was mostly quiet and stable. C1 flares: C1.7 @ 16:03 UT
Region 13531 [S20E56] was quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9251 [S14W43] developed slowly and quietly.
S9252 [S15W11] reemerged with tiny spots.
S9253 [N19E19] was quiet and stable.
S9255 [N15E58] developed slowly and quietly.
S9256 [N29E18] was quiet and stable.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C5.4 00:06 S24E31 13529 GOES16  
C3.9 02:18   13529 GOES16  
M4.2/1N 05:38 S12W61 13519 GOES16  
C2.4 07:36   13519 GOES16  
C2.0 09:40   13521 GOES16  
C2.2 10:10 N14E01 13528 GOES16 simultaneous flare in AR 13521
C2.2 10:25   13521 GOES16 simultaneous flare in AR 13519
C2.1 12:21 N08W19 13528 GOES16  
C2.1 16:25   13524 GOES16  
C2.3 16:51   13519 GOES16  
C3.1 18:03   13519 GOES16  
C4.1 19:07   13530 GOES16 incorrectly attributed to AR 13526 by SWPC
C2.0 20:30   13519 GOES16  
C2.1 20:35   13529 GOES16  
C4.0 21:21   13529 GOES16  
C2.9 23:30   13519 GOES16  
M3.3 00:04   13519 GOES16  

Coronal mass ejections (CMEs)

December 19-21: 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 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 on December 22-24. There's a slight chance of unsettled intervals on December 22-23 should effects from CH1194 reach Earth.

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
13518 2023.12.12
2023.12.12
      N13W49          

location: N14W44

13519 2023.12.12
2023.12.13
9 19 8 S12W72 0180 DAI DAO

beta-gamma

location: S09W70

area: 0120

13521 2023.12.14
2023.12.15
8 21 18 N12W07 0100 DSI DAI area: 0210
S9238 2023.12.14       N30W40            
13523 2023.12.15
2023.12.16
      N25W04           merged with AR 13524
13525 2023.12.15
2023.12.16
  3 1 S05W27 0007   BXO

location: S08W21

13522 2023.12.15
2023.12.16
  1   S03W47 0001   AXX   location: S05W42
13524 2023.12.15
2023.12.16
2 13 5 N27E05 0010 BXO CRO location: N26E03

area: 0030

13526 2023.12.16
2023.12.17
8 24 17 N15E17 0170 CAI DAC

beta-delta

location: N14E18

area: 0240

13528 2023.12.16
2023.12.18
9 24 15 N08W28 0170 DAI DAI area: 0390

location: N08W26

13529 2023.12.16
2023.12.18
18 32 18 S21E15 0430 DKO EKO

area: 0820

location: S19E14

S9247 2023.12.17       N14E02            
S9248 2023.12.17       S21W07            
13530 2023.12.18
2023.12.19
3 18 9 N08E36 0030 BXO DRI

location: N08E37

area: 0070

S9251 2023.12.18   9 7 S14W43 0030   BXO  
S9252 2023.12.19   4 2 S19W12 0010   BXO    
S9253 2023.12.19   6 2 N19E19 0013   BXO  
13531 2023.12.19
2023.12.20
1 1 1 S21E55 0070 HSX HHX area: 0320

location: S20E56

S9255 2023.12.19   7 3 N15E58 0020   CRO  
S9256 2023.12.20   4 3 N29E18 0014   BXO  
Total spot count: 58 186 109  
Sunspot number: 138 336 249  (total spot count + 10 * number of spotted regions)
Weighted SN: 93 235 158  (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): 152 185 199  

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
2023.12 147.3 (1)   83.3 (2A) / 123.0 (2B) / 155.8 (2C) (132.7 projected, -1.4) (12.3)
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.