Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 22, 2021 at 08:00 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 1, 2021)
Solar cycle Solar cycles 23-25 (December 1, 2021) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (December 1, 2021) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (June 1, 2020) POES auroral activity level October 2009 - December 2012]
  Comparison of cycles 21-25 (December 1, 2021) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (December 1, 2021) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (August 22, 2021) 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 21 under the influence of a high speed stream from CH1049. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 136.6 - increasing 53.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 80.83). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.6). Three hour interval K indices: 42212231 (planetary), 32222332 (Boulder), 53212151 (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 15 active regions using 2K resolution (SN: 309) and in 13 active regions using 1K resolution (SN: 209) SDO/HMI images.

Region 12907 [S20W38] developed further and was mostly quiet. M class flares are possible.
Region 12908 [S21W24] developed as new flux emerged. The region is unstable and could produce further M class events. C1 flares: C1.0 @ 13:52 UT.
Region 12909 [S20W11] was mostly quiet and stable.
Region 12910 [N15W77] decayed slowly and quietly.
Region 12911 [N20E02] was quiet and stable.
Region 12912 [S11E40] developed slowly and was quiet.
Region 12913 [S28E19] decayed slowly and quietly.
New region 12914 [S17E22] emerged on December 18 and was numbered by SWPC 3 days later as the region began to decay.
New region 12915 [N17E38] rotated into view on December 18 with SWPC numbering the region 3 days later. The region developed slowly on December 21.
New region 12916 [S17E80] rotated partly into view with a leading large spot. C and M class flares are possible.

Spotted regions not observed (or interpreted differently) by SWPC:
S7239 [S17W25] did not change significantly and could produce C flares. SWPC includes these spots in AR 12908.
New region S7252 [N18E48] emerged with tiny spots.
New region S7253 [N24E60] emerged with tiny spots.
New region S7254 [N20E65] emerged with tiny spots.
New region S7255 [S27E43] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
C5.5/1F 01:57 S22W30 12907 GOES16  
C2.8 03:44   12908 GOES16  
C3.3 05:00   12908 GOES16  
C4.0 06:10   12908 GOES16  
C4.9 07:22 S20W13 12908 GOES16  
M1.1 07:50 S17E90 12916 GOES16  
M1.4 11:44 S17E90 12916 GOES16  
C2.0 15:53   12916 GOES16  
C4.9 17:50 S21W17 12908 GOES16  
C4.9 19:23 S20W08 12909 GOES16 EIT wave. CME?
C3.9 20:48   12916 GOES16  
C4.9 22:37   12916 GOES16  

Coronal mass ejections (CMEs)

December 19, 21: No obviously Earth directed CMEs were observed in available LASCO imagery.
December 20: A faint halo CME was observed after the M1.8 LDE in AR 12908.

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 coronal hole (CH1049) rotated across the central meridian on December 17-18.

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. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on December 22 due to effects from CH1049 and quiet during the first half of December 23. A CME could reach Earth after noon on December 23 and cause unsettled to minor storm conditions that day and on December 24.

Coronal holes (1) Coronal mass ejection (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 red colored.

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
12910 2021.12.11
2021.12.16
3 2   N15W79 0020 CRO BXO area: 0003
12905 2021.12.11
2021.12.12
      S12W81            
12907 2021.12.12
2021.12.13
14 54 25 S21W38 0200 DAI EAI beta-gamma
12906 2021.12.13
2021.12.13
      S29W71          
12908 2021.12.14
2021.12.15
18 18 11 S20W25 0100 DSI DRI area: 0070
12909 2021.12.14
2021.12.15
3 12 6 S21W12 0080 HAX CAO  
S7239 2021.12.15   30 16 S17W25 0140   DRI  
12911 2021.12.16
2021.12.16
1 7 2 N20E02 0020 HRX CRO  
12913 2021.12.17
2021.12.20
1 3 2 S28E19 0010 AXX AXX area: 0006
12914 2021.12.18
2021.12.21
2 4 1 S17E23 0010 BXO BXO  
12912 2021.12.18
2021.12.19
1 5 3 S11E40 0030 HSX CAO

area: 0060

S7246 2021.12.18       N15W32            
12915 2021.12.18
2021.12.21
3 8 5 N16E36 0030 DSO DRO area: 0080
S7248 2021.12.18       S10W13            
S7250 2021.12.20       S21E04          
12916 2021.12.21
2021.12.21
1 3 1 S18E82 0100 HSX CHO   was AR S7251

area: 0280

location: S17E80

S7252 2021.12.21   3 1 N18E48 0012   BXO    
S7253 2021.12.21   2 2 N24E64 0010   BXO    
S7254 2021.12.21   2   N20E65 0002   BXO    
S7255 2021.12.21   6 3 S27E43 0017   BXO    
Total spot count: 47 159 79  
Sunspot number: 147 309 209  (total spot count + 10 * number of spotted regions)
Weighted SN: 83 196 116  (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): 162 170 167  

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 (solar max) 7.88
2017.09 91.3 92.3 43.6 18.2 (-1.3) 18.22
(cycle 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
2020.06 69.5 71.7 5.8 7.9 (+2.3) 3.75
2020.07 69.5 71.8 6.3 9.0 (+1.1) 4.28
2020.08 71.6 73.4 7.6 9.5 (+0.5) 5.68
2020.09 70.7 71.4 0.7 10.5 (+1.0) 8.59
2020.10 74.6 74.2 14.6 11.9 (+1.4) 6.13
2020.11 89.9 88.0 34.5 13.6 (+1.7) 4.77
2020.12 86.9 84.2 23.1 15.3 (+1.7) 4.72
2021.01 76.0 73.6 10.4 17.3 (+2.0) 4.39
2021.02 74.3 72.4 8.3 19.1 (+1.8) 9.50
2021.03 76.0 75.2 17.3 21.8 (+2.7) 10.17
2021.04 75.9 76.4 24.5 24.9 (+3.1) 8.40
2021.05 75.3 77.1 21.2 25.9 (+1.0) 6.50
2021.06 79.4 81.8 25.3 (26.9 projected, +1.0) 5.52
2021.07 81.0 83.6 34.4 (29.9 projected, +3.0) 5.51
2021.08 77.7 79.7 22.4 (34.6 projected, +4.7) 6.19
2021.09 87.0 88.2 51.5 (40.3 projected, +5.7) 6.33
2021.10 88.9 88.3 38.1 (44.7 projected, +4.4) 7.38
2021.11 86.2 84.4 35.1 (49.3 projected, +4.6) 9.9
2021.12 94.3 (1)   35.9 (2A) / 53.0 (2B) / 59.7 (2C) (55.1 projected, +5.8) (6.9)
2022.01       (58.7 projected, +3.6)  
2022.02       (63.5 projected, +4.8)  
2022.03       (68.9 projected, +5.4)  
2022.04       (74.0 projected, +5.1)  
2022.05       (80.4 projected, +6.4)  

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: SIDC-SILSO.

Solar cycles 24-25

Smoothed SF and sunspot numbers

 

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.