Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 21, 2023 at 08:55 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 20 under the influence of effects from CH1193. Solar wind speed at SOHO ranged between 412 and 632 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels.

Solar flux density measured at 20h UT on 2.8 GHz was 195.3 - increasing 1.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.09. 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: 10.3). Three hour interval K indices: 43222211 (planetary), 43232221 (Boulder), 44323433 (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 14 active regions using 2K resolution (SN: 358) and in 14 active regions using 1K resolution (SN: 266) SDO/HMI images.

Region 13519 [S09W58] developed slowly as the positive polarity penumbra to the north of the main spot gained area. That patch of positive polarity is largely within the leading negative polarity area. The region was the source of an M4.2 flare at 05:38 UT on December 21.
Region 13521 [N12E07] developed further and could produce a minor M class flare. C1 flares: C1.8 @ 02:34, C1.9 @ 07:55 UT
Region 13524 [N27E17] developed slowly and was mostly quiet.
Region 13525 [S08W06] decayed slowly and quietly.
Region 13526 [N14E31] developed slowly and could produce a minor M class flare.
Region 13528 [N08W13] developed slowly and has M class flare potential.
Region 13529 [S20E27] gained area as the main spots enlarged. The region is currently not very complex, but there is still a small chance of a major flare.
Region 13530 [N08E50] decayed and has only rudimentary penumbra on both leading and trialing spots.
New region 13531 [S20E69] rotated into view on December 19 and was numbered the next day by SWPC. C1 flares: C1.9 @ 23:38 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9251 [S14W29] was quiet and stable.
S9253 [N21E30] was quiet and stable.
S9255 [N14E70] was quiet and stable.
New region S9256 [N30E32] emerged with tiny spots.
New region S9257 [S20W56] emerged with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.8 04:46   13521 GOES16  
C7.9 06:03 N10E17 13521 GOES16  
C2.4 06:33   13521 GOES16  
C2.3 08.35   13521 GOES16  
C8.3 08:54 N10E15 13521 GOES16  
C7.9 09:36 S10W50 13519 GOES16  
C2.3 11:39   13521 GOES16  
C3.7 13:45   13519 GOES16  
C3.2 14:10   13526 GOES16  
C3.8 14:36 N08E54 13530 GOES16  
C2.3 15:54   13529 GOES16  
C2.5 16:28   13530 GOES16 attributed to AR 13526 by SWPC
C3.3 16:34   13529 GOES16  
C2.5 17:00   13530 GOES16  
C6.8 17:27   13519 GOES16 attributed by SWPC to weaker, simultaneous flare in AR 13531
C7.2 18:43   13521 GOES16  
C3.8 18:53   13531 GOES16  
C2.5 19:15   13529 GOES16  
C2.4 19:33   13531 GOES16  
C3.4 20:17   13531 GOES16 simultaneous flare in AR 13529. Incorrectly attributed to AR 13524 by SWPC
C4.4 21:01   13529 GOES16 incorrectly attributed to AR 13524 by SWPC
C6.6 21:54   13519 GOES16  
C3.3 22:29   13529 GOES16  
C2.5 22:59   13526 GOES16  

Coronal mass ejections (CMEs)

December 18-20: 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 to unsettled on December 21 due to lingering effects from CH1193. 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
13516 2023.12.08
2023.12.08
      S18W82          

location: S17W78

13518 2023.12.12
2023.12.12
      N13W35        

location: N14W31

13519 2023.12.12
2023.12.13
9 23 14 S11W58 0140 ESO DSI

location: S09W58

13521 2023.12.14
2023.12.15
4 34 21 N11E03 0080 DSO DAI area: 0240

location: N12E07

S9238 2023.12.14       N30W27            
13523 2023.12.15
2023.12.16
2     N25E10 0010 BXO       merged with AR 13524
13525 2023.12.15
2023.12.16
  5 2 S05W12 0010   BXO

location: S08W06

13522 2023.12.15
2023.12.16
      S03W32         location: S02W26
13524 2023.12.15
2023.12.16
  23 12 N26E08 0060   DRO location: N27E17
13526 2023.12.16
2023.12.17
6 29 17 N15E30 0200 CAO DAC

location: N14E31

13528 2023.12.16
2023.12.18
9 35 19 N09W14 0140 DAI DAI area: 0370

location: N08W13

13529 2023.12.16
2023.12.18
6 35 23 S19E27 0450 DKI EKO beta-gamma

area: 0810

location: S20E27

13527 2023.12.17 2     S01W83 0025 CAO    

location: S01W85

rotated out of view

S9247 2023.12.17       N14E15            
S9248 2023.12.17       S21E06            
S9249 2023.12.17       N21W58            
13530 2023.12.18
2023.12.19
4 17 9 N08E49 0180 DAO ERI beta-gamma

location: N08E50

area: 0090

S9251 2023.12.18   5 2 S14W29 0010   BXO  
S9252 2023.12.19       S19E01          
S9253 2023.12.19   4 1 N21E30 0010   BXO  
13531 2023.12.19
2023.12.20
1 2 2 S20E68 0060 HAX HSX area: 0240
S9255 2023.12.19   5 1 N14E70 0012   BXO  
S9256 2023.12.20   2 2 N30E32 0005   BXO    
S9257 2023.12.20   1 1 S20W56 0002   AXX    
Total spot count: 43 218 126  
Sunspot number: 133 358 266  (total spot count + 10 * number of spotted regions)
Weighted SN: 83 259 167  (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): 133 197 213  

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
2023.12 145.0 (1)   78.9 (2A) / 122.3 (2B) / 154.4 (2C) (132.7 projected, -1.4) (12.7)
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.