Solar Terrestrial Activity Report

Activity chart

Last major update issued on January 1, 2024 at 17:20 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 (January 1, 2024)
Solar cycle Solar cycles 23-25 (January 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (January 1, 2024) 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 (January 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (January 1, 2024) 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 very quiet on December 31. Solar wind speed at SOHO ranged between 283 and 370 km/sec. The high latitude magnetometer at Andenes recorded quiet to unsettled levels.

Solar flux density measured at 20h UT on 2.8 GHz was 146.2 - increasing 8.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.48. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.71 on June 27, 2023). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.6). Three hour interval K indices: 01000111 (planetary), 01102223 (Boulder), 00000223 (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 13 active regions using 2K resolution (SN: 202) and in 8 active regions using 1K resolution (SN: 104) SDO/HMI images.

Region 13531 [S19W75] was mostly quiet and stable.
Region 13533 [N13W83] decayed further and was quiet.
Region 13534 [S13E05] decayed slowly and quietly.
New region 13536 [N05E75] rotated into view as a compact and complex region with a very tight magnetic delta structure in the northern section. Another X class event is possible as long as the current delta persists. C1 flares: C1.2 @ 04:39, C1.4 @ 05:05, C1.2 @ 05:59, C1.5 @ 07:41, C1.5 @ 11:10, C1.9 @ 17:26 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9269 [N19W09] was quiet and stable.
S9273 [S13E24] was quiet and stable.
New region S9276 [N17W21] emerged with a few tiny spots.
New region S9278  [S09W51] emerged with tiny spots.
New region S9279 [N07E84] rotated partly into view trailing AR 13536. C1 flares: C1.3 @ 10:15 UT
New region S9280 [N20E06] was observed with tiny spots in an old plage area.
New region S9281 [N08E45] was observed with tiny spots in an old plage area.
New region S9282 [S20E09] was observed with tiny spots in an old plage area.
New region S9283 [N22E52] emerged with tiny spots early in the day, then decayed slowly.

AR 13530 at the northwest limb was the source of several C1 flares: C1.4 @ 01:14, C1.3 @ 02:52, C1.2 @ 04:46, C1.2 @ 10:01 UT

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.1 00:19   13536 GOES16  
C4.2 03:13   13530 GOES16  
C2.4 08:09   13530 GOES16  
C9.6 08:17   13536 GOES16  
C6.2 08:25   13536 GOES16  
C8.3 09:12   13536 GOES16 simultaneous flare in AR 13530
C2.7 12:07   13530 GOES16  
C5.5 12:55   13536 GOES16  
C3.8 13:34   13536 GOES16  
C5.2 14:07   13536 GOES16  
C4.8 14:35   13536 GOES16  
C4.7 14:53   13536 GOES16  
C4.3 15:06   13530 GOES16  
C3.8 16:11   13536 GOES16  
C2.4 17:46   13536 GOES16  
C3.8 18:15   13536 GOES16  
C4.2 18:39   13536 GOES16  
M1.0 19:12   13536 GOES16  
C6.6 20:37   13536 GOES16  
X5.0/3B 21:55   13536 GOES16 moderate type IV radio sweep
very fast partial halo CME

Coronal mass ejections (CMEs)

December 29-30: No obviously Earth directed CME observed.
December 31: A very fast partial halo CME was observed after the X5 flare in AR 13536. While Earth is not in the path of the main ejecta, there is a substantial chance of strong effects when the CME reaches Earth, probably on January 2 or 3.

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 recurrent negative polarity trans equatorial coronal hole (CH1195) was Earth facing on December 28-31.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to active on January 1-3 due to effects from CH1195. The December 31 CME could reach Earth on January 2 or 3 and cause active to major storm conditions.

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
13531 2023.12.19
2023.12.20
1 1 1 S20W77 0160 HSX HHX area: 0270

location: S19W75

13533 2023.12.19
2023.12.22
2 1 1 N14W78 0020 BXO AXX area: 0007
13535 2023.12.24
2023.12.28
      S05W60          

location: S06W58

S9263 2023.12.25       N08W34            
13534 2023.12.26
2023.12.27
10 24 8 S13E03 0120 DAO DAO

location: S13E05

S9267 2023.12.27       N23W52            
S9269 2023.12.27   3   N19W09 0003   BXO  
S9271 2023.12.29       N00W15            
S9272 2023.12.29       N18W45          
S9273 2023.12.29   4 1 S13E24 0010   AXX  
S9274 2023.12.29       S20W39            
S9275 2023.12.30       S02W05          
S9276 2023.12.31   3 2 N17W21 0010   BXO    
13536 2023.12.31
2023.12.31
2 16 7 N05E75 0080 HAX DAC   beta-delta

was AR S9277

area: 0150

S9278 2023.12.31   4 2 S09W51 0009   CRO    
S9279 2023.12.31   4 2 N07E84 0050   CAO    
S9280 2023.12.31   2   N20E06 0005   BXO    
S9281 2023.12.31   2   N08E45 0002   AXX    
S9282 2023.12.31   6   S20E09 0012   BXO    
S9283 2023.12.31   2   N22E52 0002   BXO    
Total spot count: 15 72 24  
Sunspot number: 55 202 104  (total spot count + 10 * number of spotted regions)
Weighted SN: 30 100 52  (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): 61 111 83  

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
2023.06 161.7 166.8 160.5 125.0 (+1.1)
(SC25 solar max candidate)
8.95
2023.07  176.4 182.2 159.1 (124.6 projected, -0.4) 8.15
2023.08  153.7 157.6 114.8 (124.1 projected, -0.5) 7.19
2023.09  154.4 156.0 133.6 (123.8 projected, -0.3) 14.26
2023.10  142.8 141.9 99.4 (124.6 projected, +0.8) 8.16
2023.11 153.5 150.2 105.4 (124.6 projected, +0.0) 12.20
2023.12 151.1 146.4 114.2 (121.2 projected, -3.4) 9.7
2024.01 (1)   (2A/2B) / 136.2 (2C) (117.9 projected, -3.3) ()
2024.02       (117.1 projected, -0.8)  
2024.03       (116.6 projected, -0.5)  
2024.04       (116.6 projected, +0.0)  
2024.05       (117.0 projected, -0.8)  
2024.06       (114.9 projected, -2.1)  

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.