Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 31, 2023 at 05:45 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 (May 29, 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 quiet on May 30. Solar wind speed at SOHO ranged between 374 and 411 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels.

Solar flux density measured at 20h UT on 2.8 GHz was 162.0 - increasing 5.8 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 141.47. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.1). Three hour interval K indices: 10111112 (planetary), 10112222 (Boulder), 21022234 (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 19 active regions using 2K resolution (SN: 351) and in 17 active regions using 1K resolution (SN: 246) SDO/HMI images.

Region 13311 [N20W80] decayed slowly and was mostly quiet. C1 flares: C1.3 @ 04:17 UT
Region 13313 [N23W66] decayed slowly and quietly.
Region 13315 [S17W47] decayed slowly. One of the two magnetic deltas disappeared, the region still has M class flare potential.
Region 13316 [N08W20] decayed slowly and quietly.
Region 13317 [N28W54] was mostly quiet and stable. C1 flares: C1.6 @ 01:50 UT
Region 13318 [N24W45] was mostly quiet and stable.
Region 13319 [S19W15] developed quickly gaining many spots. An M class flare is possible. C1 flares: C1.4 @ 06:46 UT
Region 13320 [N09E58] was quiet and stable.
New region 13321 [S17E68] rotated into view on May 29 and was numbered by SWPC the next day.
New region 13322 [N17W38] emerged on May 29 with SWPC numbering the region the following day.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8595 [N19W20] was quiet and stable.
S8600 [S12W08] gained a few tiny spots and was quiet.
S8602 [N11W08] was quiet and stable.
S8606 [N09E68] was quiet and stable.
S8608 [S33E10] was quiet and stable.
New region S8609 [N19E40] emerged with tiny spots. C1 flares: C1.8 @ 19:31 UT
New region S8610 [N29E66] emerged with tiny spots.
New region S8611 [N15E27] was observed with tiny spots in an old plage area.
New region S8612 [S08E83] rotated into view with a single mature spot. C1 flares: C1.8 @ 18:06, C1.9 @ 18:51 UT

AR 13312 was the source of a C1.8 flare at 04:01 UT.
A C1.8 flare was observed at 02:33 UT from a location just behind the northeast limb.
AR 13310 from a location near the southwest limb produced C1 flares: C1.8 @ 03:13, C1.2 @ 07:34, C1.8 @ 12:35 UT.
A C1.8 flare at 05:49 UT appeared to have an origin behind the southeast limb.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.5 00:20   13310 GOES16  
C2.1 03:30   13317 GOES16  
M1.2 08:10   13310 GOES16  
M1.3 10:22   13310 GOES16  
C2.9 10:42   13315 GOES16  
M1.4/1B 13:38 S20W41 13315 GOES16  
C3.4 14:51   13321 GOES16  
C2.8 15:04   13319 GOES16  
C3.5 16:34   13310 GOES16  
C6.0 16:50   13319 GOES18  
C2.8 17:23   S8612 GOES16  
C2.3 20:23   S8612 GOES16  
C2.3 21:28   S8612 GOES16  
C3.7 22:41   S8612 GOES16  
C3.0 23:18   S8612 GOES16  

Coronal mass ejections (CMEs)

May 28-30: 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 trans equatorial coronal hole (CH1150) will rotate across the central meridian on May 31 - June 1. A southern hemisphere coronal hole (CH1151) will be Earth facing on May 29-31, however, it is uncertain if CH1151 is too far to the south to be the source of a geoeffective disturbance.

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 expected for May 31 - June 2.

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
13311 2023.05.17
2023.05.18
1 1 1 N21W80 0050 HSX HSX

location: N20W80

area: 0090

13312 2023.05.18
2023.05.19
      S25W74        

location: S23W72

13313 2023.05.18
2023.05.19
1 1 1 N24W66 0020 HSX HSX

area: 0070

location: N23W66

13315 2023.05.22
2023.05.23
14 32 12 S17W48 0540 EKO EHO beta-gamma-delta

location: S17W47

area: 0620

S8591 2023.05.24       N14W31          
13316 2023.05.24
2023.05.26
2 7 3 N08W20 0000 AXX CRO area: 0012
S8593 2023.05.25       N26W52            
S8594 2023.05.26       N08W32            
S8595 2023.05.26   5   N19W20 0007   BXO  
S8596 2023.05.27       N01W30            
13318 2023.05.27
2023.05.29
3 11 5 N25W46 0110 DSO DSO area: 0140

location: N24W45

S8598 2023.05.27       S09W25            
13319 2023.05.27
2023.05.29
13 46 25 S18W15 0070 DAI EAI area: 0330

location: S19W15

S8600 2023.05.27   11 3 S12W08 0020   BXO  
13317 2023.05.28
2023.05.29
3 7 5 N27W54 0030 DRO DAO area: 0070

location: N28W54

S8602 2023.05.28   2 2 N11W08 0008   BXO  
13320 2023.05.28
2023.05.29
1 1 1 N09E58 0040 HSX HSX area: 0090
13321 2023.05.29
2023.05.30
1 2 2 S16E66 0120 HSX HKX

area: 0310

location: S17E68

S8606 2023.05.29   4 2 N09E68 0012   AXX  
13322 2023.05.29
2023.05.30
5 14 7 N16W38 0010 BXO DRO location: N17W38

area: 0050

S8608 2023.05.29   1   S33E10 0001   AXX  
S8609 2023.05.30   5 2 N19E40 0010   BXO    
S8610 2023.05.30   5 2 N29E66 0012   BXO    
S8611 2023.05.30   5 2 N15E27 0010   AXX    
S8612 2023.05.30   1 1 S08E83 0130   HSX    
Total spot count: 44 161 76  
Sunspot number: 144 351 246  (total spot count + 10 * number of spotted regions)
Weighted SN: 87 222 137  (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): 158 193 197  

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
2023.05 155.4 (1)   121.0 (2A) / 125.0 (2B) / 155.8 (2C) (129.3 projected, +5.6) (11.0)
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.