Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 24, 2023 at 09:00 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 on December 23. Solar wind speed at SOHO ranged between 310 and 405 km/sec. The high latitude magnetometer at Andenes recorded quiet to unsettled levels. A weak disturbance began after noon and appears to be caused by an unidentified positive polarity coronal hole.

Solar flux density measured at 20h UT on 2.8 GHz was 174.2 - decreasing 6.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.51. In comparison SC24 peaked on June 28, 2014 at 145.50. The next projected SC25 peak: 158.89 on July 7, 2023). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.0). Three hour interval K indices: 01212211 (planetary), 00322321 (Boulder), 20012303 (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 11 active regions using 2K resolution (SN: 289) and in 10 active regions using 1K resolution (SN: 183) SDO/HMI images.

Region 13521 [N11W35] decayed further and was quiet.
Region 13524 [N22W29] decayed slowly and quietly.
Region 13526 [N13W08] decayed significantly and was quiet.
Region 13528 [N08W53] decayed slowly and was mostly quiet. C1 flares: C1.5 @ 15:01, C1.4 @ 16:00 UT
Region 13529 [S20W13] was mostly quiet and stable. C1 flares: C1.2 @ 21:46 UT
Region 13530 [N08E08] developed slowly and produced a few C flares. C1.6 @ 07:56, C1.7 @ 15:19 UT
Region 13531 [S20E29] was quiet and stable.
Region 13532 [S14W71] decayed slowly and was mostly quiet.
Region 13533 [N15E29] developed slowly and quietly.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
New region S9259 [N17E14] emerged with a tiny spot.
New region S9260 [N28E10] was observed with tiny spots in an old plage area.

AR 13519 behind the southwest limb produced several C1 flares:  C1.4 flare @ 05:24, C1.5 flare @ 05:43, C1.6 @ 05:58, C1.9 @ 12:34 UT

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C3.1 09:14 N06E17 13530 GOES16  
C2.9 09:42 N06E17 13530 GOES16  
C2.2 14:32   13519 GOES16  
C2.3 17:41   13530 GOES16  

Coronal mass ejections (CMEs)

December 21-23: 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on December 24 and quiet on December 25-26.

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
13518 2023.12.12
2023.12.12
      N13W77          

location: N14W70

13521 2023.12.14
2023.12.15
6 14 7 N11W34 0050 CSO CAO area: 0070

location: N11W35

13523 2023.12.15
2023.12.16
      N25W32           merged with AR 13524
13525 2023.12.15
2023.12.16
      S05W57        

location: S09W45

13522 2023.12.15
2023.12.16
      S03W77           location: S05W70
13524 2023.12.15
2023.12.16
  6 3 N25W25 0012   AXX location: N22W29
13526 2023.12.16
2023.12.17
8 29 9 N15W09 0130 CAI CRI

location: N13W08

area: 0090

13528 2023.12.16
2023.12.18
11 20 13 N08W54 0200 DAI DKO

area: 0380

location: N08W40

13529 2023.12.16
2023.12.18
5 32 15 S20W12 0420 EKO EHO

area: 0730

location: S20W13

S9247 2023.12.17       N14W24            
S9248 2023.12.17       S21W33            
13530 2023.12.18
2023.12.19
5 30 17 N08E07 0030 CRO ERI

beta-gamma

location: N08E08

area: 0090

13532 2023.12.18
2023.12.22
2 9 3 S15W71 0020 BXO CRO

location: S14W71

S9252 2023.12.19       S18W26          
S9253 2023.12.19       N19W06          
13531 2023.12.19
2023.12.20
1 14 5 S20E29 0090 HAX HHX area: 0330
13533 2023.12.19
2023.12.22
5 17 10 N15E29 0020 BXO DRI area: 0090
S9256 2023.12.20       N29W08            
S9258 2023.12.22       N19W37          
S9259 2023.12.23   2 1 N17E14 0010   HRX    
S9260 2023.12.23   6   N28E10 0012   AXX    
Total spot count: 43 179 83  
Sunspot number: 123 289 183  (total spot count + 10 * number of spotted regions)
Weighted SN: 76 229 133  (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): 135 159 146  

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
2023.12 150.2 (1)   92.4 (2A) / 124.5 (2B) / 153.6 (2C) (132.7 projected, -1.4) (11.6)
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.