Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 19, 2021 at 09:05 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 on December 18. The high latitude magnetometer at Andenes recorded quiet to active levels.

Solar flux density measured at 20h UT on 2.8 GHz was 121.3 - increasing 42.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 80.49). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.1). Three hour interval K indices: 10011121 (planetary), 00021211 (Boulder), 10000042 (Andenes).

The background x-ray flux is at the class B4 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 13 active regions using 2K resolution (SN: 273) and in 11 active regions using 1K resolution (SN: 185) SDO/HMI images.

Region 12906 [S29W30] decayed slowly and quietly.
Region 12907 [S21E01] developed as negative polarity flux emerged within the trailing positive polarity area. C and M class flares are possible.
Region 12908 [S20E16] decayed slowly and quietly.
Region 12909 [S21E28] was mostly quiet and stable. C1 flares: C1.1 @ 01:54 UT
Region 12910 [N13W42] decayed slowly and quietly.
Region 12911 [N19E39] was quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC:
S7239 [S17E11] decayed slowly and quietly. SWPC includes these spots in AR 12908.
S7243 [S27E55] decayed early in the day then reemerged with a few tiny spots.
New region S7244 [S18E61] emerged with several spots.
New region S7245 [S11E80] rotated into view with a single spot.
New region S7246 [N25E07] emerged with a tiny spot.
New region S7247 [N17E80] rotated into view with tiny spots.
New region S7248 [S10E26] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
C6.3 18:01 S19E90   GOES16 LDE

Coronal mass ejections (CMEs)

December 16-18: 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]

A trans equatorial coronal hole (CH1049) will rotate across the central meridian on December 17-19.

Propagation

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

Forecast

The geomagnetic field is expected to be quiet on December 19. Quiet to active conditions are expected for December 20-22 due to effects from CH1049.

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
2 11 4 N12W44 0010 BXO BXO location: N13W42
12905 2021.12.11
2021.12.12
      S12W38          
12907 2021.12.12
2021.12.13
24 47 27 S19W01 0310 DKI EAI location: S21E01
S7233 2021.12.12       S19W29            
12906 2021.12.13
2021.12.13
4 4 2 S29W30 0020 CRO CRO  
S7236 2021.12.13       N29W30            
12908 2021.12.14
2021.12.15
15 28 15 S19E15 0270 DKI DAO area: 0200

location: S20E16

12909 2021.12.14
2021.12.15
6 16 10 S21E29 0210 DAO DAO area: 0180
S7239 2021.12.15   7 5 S17E11 0030   CRO SWPC includes this in AR 12908
12911 2021.12.16 6 13 5 N20E39 0080 CAO CAO area: 0050
S7242 2021.12.17       N15W21          
S7243 2021.12.17   3 1 S27E55 0007   AXX  
S7244 2021.12.18   8 4 S18E61 0020   CRO    
S7245 2021.12.18   1 1 S11E80 0040   HSX    
S7246 2021.12.18   1   N15E07 0001   AXX    
S7247 2021.12.18   2 1 N17E80 0006   BXO    
S7248 2021.12.18   2   S10E26 0002   BXO    
Total spot count: 57 143 75  
Sunspot number: 117 273 185  (total spot count + 10 * number of spotted regions)
Weighted SN: 90 177 108  (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): 129 150 148  

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 87.3 (1)   24.0 (2A) / 41.3 (2B) / 47.9 (2C) (55.1 projected, +5.8) (5.8)
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.