Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 21, 2023 at 09:45 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 (May 1, 2023)
Solar cycle Solar cycles 23-25 (May 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (May 1, 2023) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (July 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (May 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (May 1, 2023) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (April 5, 2023) 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 unsettled to major storm on May 20 due to effects associated with CH1148. Solar wind speed at SOHO ranged between 386 and 652 km/sec. The high latitude magnetometer at Andenes recorded unsettled to major storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 169.6 - increasing 34.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 140.74. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 35 (STAR Ap - based on the mean of three hour interval ap indices: 35.3). Three hour interval K indices: 65543333 (planetary), 45643433 (Boulder), 66643444 (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 12 active regions using 2K resolution (SN: 309) and in 9 active regions using 1K resolution (SN: 174) SDO/HMI images.

Region 13302 [N17W70] decayed slowly and quietly.
Region 13305 [N11W69] gained area and developed during the first half of the day, then decayed slowly.
Region 13307 [S10W34] reemerged with tiny spots.
Region 13308 [N11W53] was quiet and stable.
Region 13310 [S21E35] displayed only minor changes and was mostly quiet. An M class flare is possible.
Region 13311 [N18E49] expanded and became less compact. The region still has polarity intermixing and multiple magnetic deltas. Further major flares are possible.
Region 13312 [S24E58] has many small positive polarity spots and only a few negative polarity spots. Further M class flares are possible.
Region 13313 [N21E63] was quiet and stable.
New region 13314 [N14E38] emerged on May 19 and was numbered by SWPC the following day.

Spotted regions not observed (or interpreted differently) by SWPC:
S8574 [N24W05] was quiet and stable.
S8575 [N31E21] was quiet and stable.
New region S8577 [N25W60] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.9 00:23   13312 GOES16  
C2.7 00:47   13305 GOES16  
C2.8 02:05   13311 GOES16  
C4.9 02:33   13311 GOES16  
C5.4 02:40   13311 GOES16  
C5.1 03:17   13305 GOES16 simultaneous flare in AR 13311
C3.9 03:35   13311 GOES16  
C3.2 04:24   13312 GOES16  
C6.9 04:50   13312 GOES16  
C2.6 05:14   13309 GOES16  
C3.2 05:53   13311 GOES16  
C2.7 06:12   13311 GOES16  
M1.0 07:02 N19E72 13311 GOES16  
M6.5/1N 07:32 N19E72 13311 GOES16  
M1.4 08:36   13311 GOES16  
M1.1 08:55   13305 GOES16  
M1.1 09:27   13312 GOES16 simultaneous flares in ARs 13305 and 13311
C6.7 10:12   13311 GOES16  
M1.6 10:54   13311 GOES16  
C5.9 11:33   13312 GOES16  
M8.9 12:35   13311 GOES16  
C7.2 14:25   13311 GOES16  
M5.6 15:00   13311 GOES16  
C3.8 16:23   13311 GOES16  
C4.1 16:54   13311 GOES16  
C4.9 17:05   13311 GOES16  
C3.4 17:14   13311 GOES16  
C3.7 17:46   13311 GOES16  
C4.7 18:08   13311 GOES16 simultaneous flare in AR 13309
C7.2 18:54   13311 GOES16  
M1.1 19:03   13311 GOES16  
C3.6 19:45   13312 GOES16  
C4.3 19:51   13311 GOES16  
C5.1 20:17   13305 GOES16  
C6.4 20:28   13311 GOES16  
C6.1 21:04   13309 GOES16 simultaneous flare in AR 13311
M5.2 23:06   13311 GOES16  

Coronal mass ejections (CMEs)

May 18-20: No obviously Earth directed CMEs were observed.

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 trans equatorial coronal hole (CH1148) was Earth facing on May 16-17. A southern hemisphere coronal hole (CH1149) will rotate across the central meridian on May 20-22.

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 geomagnetic conditions are likely on May 21-22. A high speed stream from CH1149 could cause unsettled to major storm conditions May 23-25.

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
13301 2023.05.08
2023.05.09
      N14W79          

location: N14W75

13302 2023.05.08
2023.05.09
1 1 1 N18W72 0030 HSX HSX area: 0070

location: N17W70

13305 2023.05.12 15 25 12 N12W71 0250 DKI DAI

location: N11W69

area: 0280

13308 2023.05.14
2023.05.16
8 23 11 N12W54 0050 CAO DRI

location: N11W53

area: 0090

13307 2023.05.14
2023.05.15
  4   S09W34 0005   BXO  

location: S10W34

S8565 2023.05.14       S21W48            
S8566 2023.05.15       N21W24            
13310 2023.05.16
2023.05.17
6 22 9 S20E34 0310 CKO CKO location: S21E35

area: 0690

S8569 2023.05.16       S30W10          
13311 2023.05.17
2023.05.18
18 71 35 N18E47 0410 EKC FAC beta-gamma-delta

location: N18E49

area: 0620

13312 2023.05.18
2023.05.19
6 24 11 S25E57 0030 CAI CRI area: 0100

location: S24E58

13313 2023.05.18
2023.05.19
1 1 1 N22E63 0050 HSX HSX

location: N21E63

area: 0230

13314 2023.05.19
2023.05.20
3 8 3 N15E36 0020 BXO DRO  
S8574 2023.05.19   3 1 N25W05 0006   BXO  
S8575 2023.05.19   1   N31E21 0002   AXX  
S8576 2023.05.19       S22W43          
S8577 2023.05.20   2   N25W60 0004   AXX    
Total spot count: 58 185 84  
Sunspot number: 138 305 174  (total spot count + 10 * number of spotted regions)
Weighted SN: 108 214 123  (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): 152 168 139  

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 (SC24 solar max) 7.88
2017.09 91.3 92.3 43.6 18.2 (-1.3) 18.22
(SC24 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
2021.09 87.0 88.2 51.3 40.2 (+4.8) 6.33
2021.10 88.9 88.3 37.4 45.2 (+5.0) 7.38
2021.11 86.2 84.4 34.8 50.8 (+5.6) 9.83
2021.12 103.0 99.8 67.5 55.9 (+5.1) 6.40
2022.01 103.8 100.5 55.3 60.1 (+4.2) 8.92
2022.02 109.1 106.5 60.9 64.7 (+4.6) 10.46
2022.03 117.0 115.8 78.6 68.7 (+4.0) 10.20
2022.04 130.8 131.7 84.0 73.0 (+4.3) 11.79
2022.05 133.8 136.8 96.5 77.4 (+4.4) 7.48
2022.06 116.1 119.8 70.3 81.1 (+3.7) 8.20
2022.07 125.4 129.5 91.4 86.7 (+5.6) 9.51
2022.08 114.2 117.1 74.6 92.5 (+5.8) 10.92
2022.09 135.1 136.5 96.0 96.4 (+3.9) 12.18
2022.10 133.5 132.7 95.5 98.7 (+2.3) 11.16
2022.11 123.4 120.7 80.5 (100.4 projected, +1.7) 9.33
2022.12 147.9 143.4 112.8 (104.1 projected, +3.7) 10.99
2023.01 182.4 176.6 143.6 (110.1 projected, +6.0) 8.73
2023.02 167.2 163.2 110.9 (115.2 projected, +5.1) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 122.6 (118.3 projected, +3.1) 14.42
2023.04 145.4 146.4 96.4 (123.7 projected, +5.4) 13.40
2023.05 154.8 (1)   78.7 (2A) / 122.1 (2B) / 147.4 (2C) (129.3 projected, +5.6) (11.3)
2023.06       (132.5 projected, +3.2)  
2023.07       (132.0 projected, -0.5)  
2023.08       (133.0 projected, +1.0)  
2023.09       (136.4 projected, +3.4)  
2023.10       (138.3 projected, +1.9)  
2023.11       (141.4 projected, +3.1)  
2023.12       (142.5 projected max SC25)  

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.