Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 17, 2023 at 10:05 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 16 under the influence of CME effects. Solar wind speed at SOHO ranged between 409 and 520 km/sec. The high latitude magnetometer at Andenes recorded quiet to major storm levels. A distubance related to the December 14 was in progress at DSCOVR at 07:33 UT (the exact start time is not yet clear due to a data gap after 05:56 UT) on December 17.

Solar flux density measured at 20h UT on 2.8 GHz was 149.0 - increasing 8.9 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 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.0). Three hour interval K indices: 44323133 (planetary), 34222222 (Boulder), 55411054 (Andenes).

The background x-ray flux is at the class C2 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 272) and in 11 active regions using 1K resolution (SN: 168) SDO/HMI images.

Region 13513 [N18W82] was mostly quiet and stable.
Region 13514 [N04W81] decayed further and produced many C flares. An M class flare is possible while the region is rotating over the northwest limb. C1 flares: C1.9 @ 07:33, C1.5 @ 12:10, C1.9 @ 12:32, C1.6 @ 18:30, C1.6 @ 21:03 UT
Region 13516 [S18W26] decayed slowly and quietly.
Region 13517 [N14W67] reemerged with a tiny spot.
Region 13518 [N14E22] decayed slowly and quietly.
Region 13519 [S09W02] was mostly quiet and stable. Slight decay was observed in the leading penumbra.
Region 13520 [N08W75] was mostly quiet and stable.
Region 13521 [N11E59] was quiet and stable.
New region 13522 [S03E27] emerged on December 15 and was numbered the next day by SWPC as the region began to decay.
New region 13523 [N21E64] rotated into view on December 15 with SWPC numbering the region the following day.
New region 13524 [N26E65] rotated into view on December 15 and received its NOAA number the next day.
New region 13525 [S08E36] emerged on December 15 and was numbered by SWPC the next day.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9238 [N30E12] reemerged with tiny spots.
New region S9243 [N16E83] rotated into view with tiny spots.
New region S9244 [N09E42] was observed with tiny spots in an old plage area. C1 flare: C1.5 @ 21:22 UT
New region S9245 [S19E79] rotated into view with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.6 00:13   13514 GOES16  
C2.1 02:12   13514 GOES16  
C2.1 02:40   13514 GOES16  
C4.0 03:09   13514 GOES16  
C2.3 03:34   13514 GOES16  
C3.6 05:46   13514 GOES16  
C2.2 06:51   13514 GOES16  
C2.3 07:53   13514 GOES16  
C2.1 09:09   13514 GOES16  
C2.6 11:07   13514 GOES16  
C2.5 11:15   13514 GOES16  
C2.6 11:33   13513 GOES16  
C2.1 13:10   13514 GOES16  
C8.3 13:54   13514 GOES16 LDE
C7.7 14:36   13514 GOES16  
C5.2 15:20   13514 GOES16  
C3.0 15:54   13514 GOES16  
C2.3 16:43   13514 GOES16  
C2.1 17:35   13514 GOES16  
C2.7 17:44   13514 GOES16  
C2.0 19:22   13514 GOES16  
C3.2 19:55   13514 GOES16  
C2.1 22:21   13514 GOES16  

Coronal mass ejections (CMEs)

December 14: An asymmetric full halo CME was observed after the X2.8 flare in AR 13514. The CME reached Earth on December 17.
December 15: A partial halo CME was observed after the M6 flares AR 13514. The CME could reach Earth on December 18 and unsettled and active intervals.
December 16: 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 to very poor. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to major storm on December 17 due to effects from the December 14 CME. Effects from CH1193 could reach Earth late on December 17 and cause quiet to minor storm conditions until December 19. The December 15 CME could reach Earth on December 18 and contribute to the ongoing 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
13513 2023.12.04
2023.12.05
1 1 1 N18W82 0079 HSX HSX  
13514 2023.12.05
2023.12.06
12 11 6 N05W82 0300 EKC EAC

beta-gamma

location: N04W81

13516 2023.12.08
2023.12.08
1 12 4 S18W29 0010 AXX BXO

location: S18W26

area: 0020

13515 2023.12.08
2023.12.08
      S14W31            
13517 2023.12.08
2023.12.11
  1   N11W69 0002   AXX   location: N14W67
S9222 2023.12.08       N13W58            
13518 2023.12.12
2023.12.12
3 7 2 N13E21 0010 AXX BXO

location: N14E22

S9232 2023.12.12       S19W40            
13519 2023.12.12
2023.12.13
18 38 26 S12W02 0130 DAI DSI location: S09W02

area: 0200

S9234 2023.12.12       S18W48            
13520 2023.12.13
2023.12.13
5 6 4 N08W75 0080 CSO DSO

area: 0110

13521 2023.12.14
2023.12.15
1 4 2 N12E57 0020 HSX HSX area: 0060

location: N11E59

S9238 2023.12.14   3   N30E12 0006   AXX    
13523 2023.12.15
2023.12.16
2 2 1 N21E62 0020 HRX HRX  
13525 2023.12.15
2023.12.16
4 10 6 S09E45 0020 BXO DRO location: S09E46

area: 0045

13522 2023.12.15
2023.12.16
4 5 3 S04E25 0010 BXO BXO location: S03E27
13524 2023.12.15
2023.12.16
2 4 3 N26E63 0020 HRX HRX location: N26E65

area: 0030

S9243 2023.12.16   2   N16E83 0010   AXX    
S9244 2023.12.16   5   N09E42 0007   BXO    
S9245 2023.12.16   1   S19E79 0002   AXX    
Total spot count: 53 112 58  
Sunspot number: 163 272 168  (total spot count + 10 * number of spotted regions)
Weighted SN: 89 146 92  (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): 179 150 134  

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
2023.12 138.0 (1)   61.4 (2A) / 118.9 (2B) / 139.5 (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.