Solar Terrestrial Activity Report

Activity chart

Last major update issued on January 2, 2024 at 08:35 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 (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
Calculating the Strength of Solar Cycle 25 Using 365-day Smoothing (new)

Recent activity

The geomagnetic field was quiet to active on January 1. Solar wind speed at SOHO ranged between 300 and 407 km/sec. The high latitude magnetometer at Andenes recorded quiet to major storm levels. Effects from CH1195 became dominant after noon.

Solar flux density measured at 20h UT on 2.8 GHz was 135.7 - decreasing 5.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.44. 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 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.0). Three hour interval K indices: 00111334 (planetary), 00122323 (Boulder), 00001456 (Andenes).

The background x-ray flux is at the class B8 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 194) and in 8 active regions using 1K resolution (SN: 109) SDO/HMI images.

Region 13531 [S19W87] rotated partly out of view and was mostly quiet. C1 flares: C1.9 @ 22:49 UT
Region 13534 [S13W09] decayed significantly and was quiet.
Region 13536 [N05E62] produced many C and M flares, however, activity was less intense after the M4 flare around noon. There is still a magnetic delta structure but with more separation between opposite polarity umbrae. C1 flares: C1.5 @ 06:59, C1.5 @ 15:36, C1.3 @ 18:41, C1.7 @ 19:51 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9269 [N20W22] was quiet and stable.
S9273 [S12E14] was quiet and stable.
S9278  [S08W64] decayed slowly and quietly.
S9279 [N07E70] produced several low level C flares. C1 flares: C1.3 @ 03:55, C1.2 @ 06:02, C1.9 @ 10:20 UT
S9282 [S18W01] decayed slowly and quietly.
S9283 [N21E37] was quiet and stable.
New region S9284 [S01E21] was observed with a tiny spot in an old plage area.
New region S9285 [N17E60] emerged with several spots and has potential for further growth. C1 flares: C1.2 @ 18:25, C1.5 @ 22:07 UT
New region S9286 [N08W12] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.1 01:38   S9279? GOES16  
C4.7 08:06   13536 GOES16  
C3.3 08:31   13536 GOES16  
M2.3/1N 08:47 N04E70 13536 GOES16  
M4.7 12:25   13536 GOES16  
C2.6 16:28 N06E67 13536 GOES16  
C2.6 16:34   13533 GOES16  
C5.7 17:04 N06E65 13536 GOES16  
C2.1 20:04   13533 GOES16  
C2.4 20:15   13536 GOES16  

Coronal mass ejections (CMEs)

December 30+January 1: 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 poor to very poor. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to active on January 2-3 due to effects from CH1195. The December 31 CME could reach Earth on January 2 or 3 and cause active to major storm conditions. Quiet to unsettled is likely on January 4.

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   S19W94 0060 HSX HHX area: 0270

location: S19W87

13535 2023.12.24
2023.12.28
      S05W75          

location: S06W71

S9263 2023.12.25       N08W47            
13534 2023.12.26
2023.12.27
8 19 7 S14W11 0010 BXO CRO

location: S13W09

area: 0040

S9269 2023.12.27   2   N20W22 0004   AXX  
S9271 2023.12.29       N00W28            
S9272 2023.12.29       N18W58            
S9273 2023.12.29   6 1 S12E14 0010   AXX  
S9274 2023.12.29       S20W52            
S9275 2023.12.30       S02W18            
S9276 2023.12.31       N17W34          
13536 2023.12.31
2023.12.31
5 13 6 N06E63 0140 EAI DKC beta-delta

area: 0270

location: N05E62

S9278 2023.12.31   3   S08W64 0003   BXO  
S9279 2023.12.31   13 7 N07E70 0100   DAI  
S9280 2023.12.31       N20W07          
S9281 2023.12.31       N08E32          
S9282 2023.12.31   4   S20W04 0010   BXO  
S9283 2023.12.31   1 1 N21E37 0004   BXO  
S9284 2024.01.01   3 1 S01E21 0005   BXO    
S9285 2024.01.01   7 4 N17E60 0040   CRO    
S9286 2024.01.01   2 2 N08W12 0007   AXX    
Total spot count: 14 74 29  
Sunspot number: 44 194 109  (total spot count + 10 * number of spotted regions)
Weighted SN: 24 105 50  (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): 48 107 87  

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
2022.05 133.8 136.8 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
2024.01 135.7 (1)   1.4 (2A) / 44 (2B) / 135.7 (2C) (117.9 projected, -3.3) (9.0)
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.