Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 15, 2023 at 08:10 UT. Minor update added at 11:55 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 14 under the influence of effects from CH1192. Solar wind speed at SOHO ranged between 320 and 415 km/sec. The high latitude magnetometer at Andenes recorded unsetted to major storm levels.

Solar flux density measured at 22h UT on 2.8 GHz was 148.0 - increasing 28.4 over the previous solar rotation. The measurements at 18 and 20h UT were flare influenced due to the X2.8 LDE at 17:02 UT. (Centered 1 year average SF at 1 AU - 183 days ago: 157.97. 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 15 (STAR Ap - based on the mean of three hour interval ap indices: 15.3). Three hour interval K indices: 44343212 (planetary), 43343312 (Boulder), 56443343 (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 9 active regions using 2K resolution (SN: 191) and in 7 active regions using 1K resolution (SN: 130) SDO/HMI images.

Region 13513 [N18W55] decayed slowly and was quiet.
Region 13514 [N05W55] developed further and is a complex and compact region with multiple magnetic delta structures. Another X class proton flare would not be a surprise. C1 flares: C1.2 @ 01:40, C1.2 @ 03:25, C1.4 @ 03:57, C1.8 @ 06:27, C1.8 @ 11:13, C1.8 @ 12:10, C1.8 @ 12:28 UT
Region 13516 [S15W02] decayed slowly and quietly.
Region 13517 [N15W41] decayed slowly and quietly.
Region 13518 [N13E47] decayed slowly and quietly.
Region 13519 [S10E23] developed slowly and was mostly quiet. C1 flares: C1.9 @ 02:29 UT
Region 13520 [N09W48] decayed slowly and was mostly quiet.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
New region S9237 [N11E84] rotated into view.
New region S9238 [N32E37] was observed with tiny spots in an old plage area.

Minor update added at 11:55 UT: A solar wind shock was recorded at 10:59 UT on December 15 at DSCOVR, probably related to the arrival of the Dec. 12/13 CME.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.0 04:09   13514 GOES18  
C3.3 04:56   13514 GOES16  
C2.0 05:07   13514 GOES16  
C2.0 05:49   13514 GOES16  
M5.8 07:44 N04W41 13514 GOES16 LDE
M1.9 08:10   13514 GOES16  
C2.5 10:07   13514 GOES16  
C2.5 13:24   13514 GOES16  
M2.3 13:48   13514 GOES16  
C4.0 15:03   13514 GOES16  
C2.7 15:35   13514 GOES16  
C2.3 15:44   13514 GOES16  
C2.1 16:13   13514 GOES16  
C2.8 16:31   13514 GOES16  
C3.7 16:40   13514 GOES16  
C4.8 16:46   13514 GOES16  
X2.8/1B 17:02 N04W51 13514 GOES16 LDE, full asymmetric halo CME, weak proton event
moderate type II and IV radio sweeps
M1.2 19:28   13514 GOES16  
C4.0 22:21   13514 GOES16  
C5.4 23:45   13520 GOES16  

Coronal mass ejections (CMEs)

December 12: No obviously Earth directed CMEs were observed.
December 13: A faint partial halo CME was observed early in the day, likely associated with a C2.8 flare in AR 13514 at 22:55 UT on December 12. The CME could reach Earth on December 15.
December 14: An asymmetric full halo CME was observed after the X2.8 flare in AR 13514. The CME could reach Earth on December 16 and cause unsettled to severe geomagnetic storm levels.

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 trans equatorial positive polarity coronal hole (CH1192) rotated across the central meridian on December 11-13. Significant decay was observed on December 12-13 due to the development of ARs 13514 and 13517. A positive polarity northern hemisphere coronal hole (CH1193) will be 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 unsetted on December 15. Quiet to active is possible initially on December 16 due to effects from the December 12/13 CME. Later in the day the December 14 CME could reach Earth and cause unsettled to severe storm levels lasting until December 17. Effects from CH1193 could reach Earth late on December 17 and cause quiet to minor storm conditions until December 19.

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
2 5 2 N18W54 0100 CAO CAO

location: N18W55

13514 2023.12.05
2023.12.06
21 34 25 N05W50 0470 EKC EKC

beta-gamma-delta

location: N05W55

area: 0800

13516 2023.12.08
2023.12.08
1 14 6 S17W01 0010 AXX CRO

location: S15W02

merged with AR 13515 on Dec. 13

area: 0020

13515 2023.12.08
2023.12.08
1     S12W01 0010 AXX        
13517 2023.12.08
2023.12.11
2 4   N11W41 0010 HAX BXO location: N15W41

area: 0008

S9222 2023.12.08       N13W32          
S9224 2023.12.08       S00W51            
S9225 2023.12.09       N05W50            
13518 2023.12.12
2023.12.12
3 4 3 N13E51 0020 CRO CAO

area: 0050

location: N13E47

S9232 2023.12.12       S19W14            
13519 2023.12.12
2023.12.13
15 29 19 S12E28 0200 DSO DAI location: S10E23

area: 0230

S9234 2023.12.12       S18W22            
13520 2023.12.13
2023.12.13
1 8 4 N07W46 0120 HSX DSO  
S9237 2023.12.14   1 1 N11E84 0030   HAX    
S9238 2023.12.14   2   N32E37 0002   AXX    
Total spot count: 46 101 60  
Sunspot number: 126 191 130  (total spot count + 10 * number of spotted regions)
Weighted SN: 79 139 98  (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): 139 100 104  

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
2023.12 136.8 (1)   51.9 (2A) / 114.9 (2B) / 134.5 (2C) (132.7 projected, -1.4) (10.7)
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.