Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 21, 2022 at 03:55 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 (March 1, 2022)
Solar cycle Solar cycles 23-25 (March 1, 2022) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (March 1, 2022) 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 (March 1, 2022) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (March 1, 2022) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (April 10, 2022) 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 unsettled on April 20. The high latitude magnetometer at Andenes recorded quiet to major storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 160 - increasing 48.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 92.74). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.4). Three hour interval K indices: 32210123 (planetary), 22211323 (Boulder), 53221116 (Andenes).

The background x-ray flux is at the class C2 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 8 active regions using 2K resolution (SN: 190) and in 6 active regions using 1K resolution (SN: 129) SDO/HMI images.

Region 12989 [N20W28] was quiet and stable.
Region 12991 [S24W10] decayed slowly and quietly.
Region 12993 [N20E22] decayed slowly and produced several C flares. Polarities are intermixed. A major M9.6 flare was recorded at 01:59 UT on April 21. If there was a CME associated with this event, there will be a strong chance of a significant geomagnetic disturbance.
Region 12994 [N13E28] has major flare potential and continued producing occasional C flares.
Region 12995 [N12E56] was quiet and stable.
New region 12996 [N23E68] rotated into view on April 19 and was numbered by SWPC the next day.

Spotted regions not observed (or interpreted differently) by SWPC:
S7505 [S17E13] was quiet and stable.
New region S7508 [N06W25] emerged with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C3.0 00:12   12994 GOES16  
C3.9 00:51 behind SW limb 12987 GOES16  
M7.1/1N 01:36 behind SW limb 12987 GOES16 simultaneous flare in AR 12994
C3.8 02:44 behind SW limb 12987 GOES16  
X2.2 03:57 behind SW limb 12987 GOES16 CME, strong type II radio sweep
C2.6 05:10 behind SW limb 12987 GOES16  
C4.0 05:40 behind SW limb 12987 GOES16  
C2.2 06:14 behind SW limb 12987 GOES16  
C2.3 08:40   12993 GOES16  
C4.2 09:55 behind SW limb 12987 GOES16  
C5.1 10:09   12993 GOES16  
C2.3 11:25 behind SW limb 12987 GOES16  
C3.0 11:52     GOES16  
M1.9 12:53 N21E38 12993 GOES16  
C3.1 13:54   12994 GOES16  
C2.4 15:57 behind SW limb 12987 GOES16  
C2.3 16:28 behind SW limb 12987 GOES16  
C7.7 17:56   12993 GOES16  
C8.9 18:40 N14E31 12994 GOES16  
C2.7 22:04   12993 GOES16  
C2.3 22:33 N22E19 12993 GOES16 simultaneous flare behind the northeast limb
C5.6 23:34 N13E28 12994 GOES16 wrongly attributed to AR 12993 by SWPC

Coronal mass ejections (CMEs)

April 18-20: 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 northern hemisphere coronal hole (CH1075) rotated across the central meridian on April 20-21.

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.

Forecast

Quiet to unsettled conditions are likely on April 21-22. Quiet to minor storm conditions are possible on April 23-24 due to effects from CH1075. If there was a CME associated with the M9.6 flare in AR 12993 early on April 21, Unsettled to severe storm conditions will be likely on April 23-24.

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 colored red.

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
12988 2022.04.10
2022.04.11
      N14W72          

location: N15W67

12989 2022.04.12
2022.04.12
  1   N18W35 0001   AXX location: N20W28
12991 2022.04.13
2022.04.14
1 7 3 S23W15 0010 HSX BXO location: S24W10
12990 2022.04.13       N16W59         location: N16W47
S7495 2022.04.14       N05W35            
S7496 2022.04.14       S25W38            
12993 2022.04.16
2022.04.16
19 51 35 N20E24 0490 DHI FAI

 

beta-gamma

location: N20E22

12994 2022.04.16
2022.04.16
8 34 24 N14E25 0610 DKO EKI

location: N13E28

beta-gamma

S7502 2022.04.16       S22W14            
S7503 2022.04.16       S29W53            
S7504 2022.04.16       N19W56            
S7505 2022.04.17   6   S17E13 0010   BXO  
12995 2022.04.18
2022.04.19
1 6 3 N14E56 0240 HSX CHO area: 0340

location: N12E56

12996 2022.04.19
2022.04.20
1 4 3 N23E65 0050 HSX CAO area: 0100
S7508 2022.04.20   1 1 N06W25 0003   AXX   likely SC 24 group
Total spot count: 30 110 69  
Sunspot number: 80 190 129  (total spot count + 10 * number of spotted regions)
Weighted SN: 65 140 99  (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): 88 105 103  

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
2020.08 71.6 73.4 7.5 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 8.2 19.0 (+1.7) 9.50
2021.03 76.0 75.2 17.2 21.7 (+2.7) 10.17
2021.04 75.9 76.4 24.5 24.8 (+3.1) 8.40
2021.05 75.3 77.1 21.2 25.8 (+1.0) 6.50
2021.06 79.4 81.8 25.0 27.7 (+1.9) 5.52
2021.07 81.0 83.6 34.3 31.4 (+3.7) 5.51
2021.08 77.7 79.7 22.0 35.3 (+3.9) 6.19
2021.09 87.0 88.2 51.3 40.0 (+4.7) 6.33
2021.10 88.9 88.3 38.1 (44.9 projected, +4.9) 7.38
2021.11 86.2 84.4 35.0 (50.5 projected, +5.6) 9.83
2021.12 103.0 99.8 67.6 (56.4 projected, +5.9) 6.40
2022.01 103.8 100.5 54.0 (60.0 projected, +3.6) 8.92
2022.02 109.1 106.5 59.7 (64.8 projected, +4.8) 10.46
2022.03 117.0 115.8 78.3 (70.2 projected, +5.4) 10.20
2022.04 122.5 (1)   42.0 (2A) / 63.0 (2B) / 89.5 (2C) (75.4 projected, +5.2) (13.0)
2022.05       (81.8 projected, +6.4)  
2022.06       (87.7 projected, +5.9)  
2022.07       (94.9 projected, +7.2)  
2022.08       (101.6 projected, +6.7)  
2022.09       (106.6 projected, +5.0)  

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.