Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 24, 2020 at 07:55 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, 2020)
Solar cycle Solar cycles 23-25 (December 1, 2020) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (December 1, 2020) 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, 2020) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (December 1, 2020) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (July 6, 2020) Cycle 25 spots (final update December 25, 2019)
  Solar cycles 24-25 using 365d smoothing (*) Recent research
    Current research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing

Recent activity

The geomagnetic field was quiet to active on December 23 under the influence of effects from CH982. The high latitude magnetometer at Andenes recorded quiet to minor storm conditions.

Solar flux at 20h UT on 2.8 GHz was 86.4 - decreasing 19.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 73.36). The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 11.6). Three hour interval K indices: 34332112 (planetary), 35332222 (Boulder), 45222234 (Andenes).

The background x-ray flux is at the class B1 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 3 active regions using 2K resolution (SN: 53) and in 2 active regions using 1K resolution (SN: 29) SDO/HMI images.

Region 12794 [S16E40] was quiet and stable.
New region 12795 [S17E68] rotated into view on December 22 and developed further on December 23 when it was numbered by SWPC. C class flaring is possible.

Spotted regions not observed (or interpreted differently) by SWPC:
New region S6670 [N26E09] emerged with a tiny spot.

An active region (S6671) developed at the southeast limb and was located at S22E80 at midnight. Tiny spots became visible early on December 24 and the region produced a B6 flare at 01:20 UT.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
           

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]

A recurrent northern hemisphere coronal hole (CH982) was in an Earth facing position on December 17-21. A new southern hemisphere coronal hole (CH983)  is developing in a plage area to the west of AR 12794 and will likely become Earth facing on December 26.

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 fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on December 24 due to effects from CH982 and quiet on December 25-27.

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
12792 2020.12.11
2020.12.12
      S22W85           location: S22W74
12793 2020.12.13
2020.12.14
      S15W62           location: S16W56
S6659 2020.12.15       S14W36            
S6663 2020.12.18       S24W39            
12794 2020.12.20
2020.12.20
1 8 1 S16E40 0180 HSX CHO area: 0360
S6665 2020.12.21       S10W05            
S6666 2020.12.22       S17W10          
S6667 2020.12.22       N24W48          
12795 2020.12.22
2020.12.23
6 14 8 S17E67 0040 CRO DAI area: 0160
S6669 2020.12.22       S30W11          
S6670 2020.12.23   1   N26E09 0001   AXX    
Total spot count: 7 23 9  
Sunspot number: 27 53 29  (total spot count + 10 * number of spotted regions)
Weighted SN: 15 36 22  (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): 30 29 23 k * (sunspot number)
As of May 7, 2016: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.80 for MSN 1K (MSN=Magnetic Sunspot Number)

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 (cycle 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)
2019.06 68.1 70.3 1.2 3.7 (-0.2) 4.26
2019.07 67.1 69.3 0.9 3.5 (-0.2) 5.36
2019.08 67.0 68.7 0.5 3.4 (-0.1) 6.79
2019.09 67.9 68.7 1.1 3.1 (-0.3) 9.81
2019.10 67.4 67.0 0.4 2.6 (-0.5) 7.53
2019.11 70.2 68.7 0.5 2.0 (-0.6)
(November 17, 2019 is
the solar minimum using 365d
smoothing for 1 AU solar flux,
NOAA SN and both
of STAR 1K and 2K SN)
4.19
2019.12 70.8 68.6 1.6 1.8 (-0.2)
(ISN 13 months smoothed
solar minimum)
3.22
2020.01 72.2 69.9 6.4 2.2 (+0.4) 4.39
2020.02 71.0 69.3 0.4 2.8 (+0.6) 6.16
2020.03 70.2 69.5 1.5 3.0 (+0.2) 5.63
2020.04 69.5 70.0 5.4 3.6 (+0.6) 5.32
2020.05 69.0 70.6 0.2 5.6 (+2.0) 3.80
2020.06 69.5 71.7 5.8 (8.1 projected, +2.5) 3.75
2020.07 69.5 71.8 6.3 (9.9 projected, +1.8) 4.28
2020.08 71.6 73.4 7.6 (12.3 projected, +2.4) 5.68
2020.09 70.7 71.4 0.7 (16.2 projected, +3.9) 8.59
2020.10 74.6 74.2 14.4 (19.5 projected, +3.3) 6.13
2020.11 89.9 88.0 34.0 (22.3 projected, +2.8) 4.77
2020.12 (87.1) (1)    15.2 (2A) / 20.5 (2B) / 32.9 (2C) (26.3 projected, +4.0) (4.4)
2021.01       (30.6 projected, +4.3)  
2021.02       (34.3 projected, +3.7)  
2021.03       (39.3 projected, +5.0)  
2021.04       (45.2 projected, +5.9)  
2021.05       (49.6 projected, +4.4)  

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
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 transition

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.