Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 24, 2021 at 11:05 UT.

The next update is scheduled for the afternoon of December 27. Then the plan is to produce 2 updates a day (one update for each day during Christmas as there is a lot of data to process with the currently active Sun) and be up to date on December 29.

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 on December 23. The high latitude magnetometer at Andenes recorded quiet to active levels.

Solar flux density measured at 20h UT on 2.8 GHz was 129.8 - increasing 37.5 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 81.09). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.6). Three hour interval K indices: 20010011 (planetary), 11111221 (Boulder), 40000031 (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 11 active regions using 2K resolution (SN: 271) and in 10 active regions using 1K resolution (SN: 165) SDO/HMI images.

Region 12907 [S20W65] developed further and could produce M class events. Many small C flares were recorded during the day. C1 flares: C1.4 @ 00:58, C1.1 @ 02:23, C1.7 @ 03:30, C1.4 @ 14:01, C1.1 @ 15:01, C1.0 @ 16:19, C1.2 @ 17:41, C1.1 @ 18:49, C1.2 @ 22:03, C1.3 @ 23:35 UT.
Region 12909 [S20W38] decayed slowly and quietly.
Region 12911 [N21W22] was quiet and stable.
Region 12912 [S11E14] decayed slowly and quietly.
Region 12915 [N17E12] developed slowly and quietly.
Region 12916 [S17E54] was mostly quiet and stable. There is a chance of M class flaring. C1 flares: C1.4 @ 12:46 UT.
Region 12917 [S27E19] developed and produced a C7 flare early on December 24. The region has weak polarity intermixing. C1 flares: C1.4 @ 13:22 UT.
Region 12918 [N20E40] displayed no major changes. C1 flares: C1.3 @ 20:46 UT.

Spotted regions not observed (or interpreted differently) by SWPC:
S7239 [S18W52] decayed slowly and quietly. SWPC includes these spots in AR 12908.
S7256 [S19E09] was quiet and stable.
New region S7257 [S26W01] was observed with tiny spots in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
C2.0 07:32 S23W57 12907 GOES16  
C2.1 08:11 S21W58 12907 GOES16  
C2.6 09:30 S20W57 12907 GOES16  

Coronal mass ejections (CMEs)

December 21-23: No obviously Earth directed CMEs were observed in available LASCO imagery.

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]

An extension (CH1050) of the northern polar coronal hole will rotate across the central meridian on December 24.

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

Forecast

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

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
12907 2021.12.12
2021.12.13
17 35 18 S22W65 0300 EKI EKI beta-gamma

location: S20W65

area: 0450

12908 2021.12.14
2021.12.15
10     S20W52 0100 CAI    

SWPC data includes AR S7239

spotless

12909 2021.12.14
2021.12.15
2 11 4 S21W39 0050 HAX CRO location: S20W38

area: 0030

S7239 2021.12.15   17 8 S18W52 0050   CRI  
12911 2021.12.16
2021.12.16
1 11 1 N20W25 0010 AXX BXO area: 0015

location: N21W22

12913 2021.12.17
2021.12.20
      S28W08            
12914 2021.12.18
2021.12.21
      S17W04            
12912 2021.12.18
2021.12.19
1 7 3 S12E13 0010 HRX CRO

area: 0030

S7246 2021.12.18       N15W58            
12915 2021.12.18
2021.12.21
2 11 4 N17E10 0030 CRO DRO area: 0040
S7248 2021.12.18       S10W39            
S7250 2021.12.20       S21W22            
12916 2021.12.21
2021.12.21
7 16 6 S16E55 0190 DSO EHO

area: 0500

location: S17E54

S7252 2021.12.21       N19E21          
S7253 2021.12.21       N24E38            
12918 2021.12.21
2021.12.22
6 23 9 N20E40 0080 DAO DSI area: 0200
12917 2021.12.21
2021.12.22
7 21 10 S27E18 0030 CRO DAI beta-gamma

area: 0130

S7256 2021.12.22   6 2 S19E09 0010   BXO  
S7257 2021.12.23   3   S26W01 0004   AXX    
Total spot count: 53 161 65  
Sunspot number: 143 271 165  (total spot count + 10 * number of spotted regions)
Weighted SN: 92 203 107  (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): 157 149 132  

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) 9.83
2021.12 97.8 (1)   45.0 (2A) / 60.6 (2B) / 65.4 (2C) (55.1 projected, +5.8) (6.8)
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.