Solar Terrestrial Activity Report

Activity chart

Last major update issued on December 21, 2021 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 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 20 under the influence of effects 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 122.7 - increasing 42.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 80.68). The Potsdam WDC planetary A index was 15 (STAR Ap - based on the mean of three hour interval ap indices: 13.1). Three hour interval K indices: 43243323 (planetary), 43243323 (Boulder), 44233335 (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 12 active regions using 2K resolution (SN: 239) and in 11 active regions using 1K resolution (SN: 175) SDO/HMI images.

Region 12906 [S29W56] decayed slowly and quietly.
Region 12907 [S20W23] developed as new flux emerged. M flares are possible as there is poor separation between opposite polarity spots in the center of the region. C1 flares: C1.3 @ 06:40, C1.2 @ 08:51, C1.1 @ 09:11, C1.4 @ 13:54, C1.4 @ 16:02, C1.0 @ 16:42 UT.
Region 12908 [S21W11] decayed quickly after the M1.8 flare just before noon. C1 flares: C1.6 @ 00:34, C1.5 @ 04:37 UT.
Region 12909 [S20E01] decayed slowly and quietly.
Region 12910 [N13W65] developed as new flux emerged.
Region 12911 [N20E15] was quiet and stable.
Region 12912 [S12E53] was quiet and stable.
New region 12913 [S28E32] rotated into view on December 17 and was numbered 3 days later by SWPC.

Spotted regions not observed (or interpreted differently) by SWPC:
S7239 [S17W11] gained many spots as new flux emerged. SWPC includes these spots in AR 12908.
S7244 [S17E36] developed slowly and quietly.
S7247 [N17E51] was quiet and stable.
New region S7250 [S21E17] emerged with tiny spots.

An active region behind the southeast limb produced many small C flares late in the day and might be capable of M class flaring. C1 flares: C1.4 @17:28, C1.5 @ 17:35, C1.4 @ 20:32, C1.6 @ 20:49 and C1.1 @ 22:54 UT.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
C4.4 03:21   12909 GOES16 EIT wave
C2.9 10:46   12907 GOES16  
M1.8/1N 11:36 S22W05 12908 GOES16 LDE, moderate type II radio sweep, faint halo CME

Coronal mass ejections (CMEs)

December 18-19: 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. The CME could reach Earth on December 23 and cause unsettled to minor storm conditions.

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 active on December 20-21 due to effects from CH1049 and quiet on December 22-23.

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 6 4 N14W65 0010 AXX DRO area: 0040
12905 2021.12.11
2021.12.12
      S12W67            
12907 2021.12.12
2021.12.13
13 35 19 S21W26 0150 DAI DAI beta-gamma

location: S20W23

area: 0200

S7233 2021.12.12       S19W55            
12906 2021.12.13
2021.12.13
1 2 1 S29W57 0010 AXX AXX area: 0005
S7236 2021.12.13       N29W56            
12908 2021.12.14
2021.12.15
10 18 10 S21W11 0100 CAI CRO area: 0050
12909 2021.12.14
2021.12.15
5 8 4 S21E01 0100 CSO CSO  
S7239 2021.12.15   22 16 S17W11 0100   DRI  
12911 2021.12.16
2021.12.16
2 7 3 N20E14 0020 HRX CRO  
S7242 2021.12.17       N15W47            
12913 2021.12.17
2021.12.20
1 4 2 S28E32 0010 AXX CRO  
S7244 2021.12.18   9 3 S17E36 0020   CRO  
12912 2021.12.18
2021.12.19
1 2 1 S12E52 0030 HSX CSO location: S12E67

area: 0060

S7246 2021.12.18       N15W19            
S7247 2021.12.18   4 2 N17E51 0012   BXO  
S7248 2021.12.18       S10W00            
S7250 2021.12.20   2   S21E17 0002   AXX    
Total spot count: 35 119 65  
Sunspot number: 115 239 175  (total spot count + 10 * number of spotted regions)
Weighted SN: 58 152 98  (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): 127 131 140  

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 92.2 (1)   31.2 (2A) / 48.4 (2B) / 54.8 (2C) (55.1 projected, +5.8) (6.6)
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.