Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 25, 2023 at 03:45 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 quiet to unsettled on May 24 under the influence of a high speed stream associated with CH1149. Solar wind speed at SOHO ranged between 508 and 631 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 164.1 - increasing 23.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 140.76. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.3). Three hour interval K indices: 23123233 (planetary), 23113423 (Boulder), 44234354 (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: 322) and in 10 active regions using 1K resolution (SN: 213) SDO/HMI images.

Region 13310 [S20W18] became slightly less complex as most of the small positive polarity spots disappeared.
Region 13311 [N19W02] decayed in the intermediate and trailing spot sections. The magnetic delta decreased in size. The leading spot section was split off into a new region. Further M class flares are possible. C1 flares: C1.5 @ 02:11, C1.8 @ 05:24, C1.9 @ 22:23 UT
Region 13312 [S25E04] decayed slowly and was mostly quiet. C1 flares: C1.4 @ 12:52, C1.5 @ 13:15 UT
Region 13313 [N22E11] was quiet and stable.
Region 13315 [S18E33] developed significantly and has minor polarity intermixing. Further M class flares are possible.

Spotted regions not observed (or interpreted differently) by SWPC:
S8580 [N20W27] was quiet and stable.
S8586 [S28W45] decayed slowly and quietly.
New region S8588 [S13W13] emerged with several spots to the north of AR 13310.
New region S8589 [S20E12] was observed with tiny spots in an old plage area.
New region S8590 [N15W17] was split off from AR 13311 as negative polarity spots emerged to the southeast of the previous leader spot of that region.
New region S8591 [N11E50] emerged with a tiny spot.
New region S8592 [N08E63] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.7 03:50   13311 GOES16  
C2.8 04:08   13311 GOES16  
C2.4 07:59   S8590 GOES16 incorrectly attributed to AR 13312 by SWPC
C5.0 08:37   13311 GOES16  
C2.3 09:31   13311 GOES16  
M1.0 09:58   13311 GOES16  
C5.9 10:06   S8590 GOES16  
C6.7 10:26   13311 GOES16  
C2.0 13:47   13311 GOES16  
C2.4 15:01   13311 GOES16  
C2.7 15:32   13311 GOES16  
C2.0 16:24   13311 GOES16  
C4.3 17:10   13311 GOES16  
M1.9/1F 17:26   13311 GOES16  
M1.0 18:00   13315 GOES16  
C3.1 18:48   13315 GOES16  
C3.8 18:55   13311 GOES16  
C5.1 19:10   13311 GOES16 incorrectly attributed to AR 13312 by SWPC
C3.5 19:51   13311 GOES16  
C2.8 20:12   13311 GOES16  
C2.3 22:23   13311 GOES16 simultaneous flare in AR S8590
C2.6 22:41   13312 GOES16  

Coronal mass ejections (CMEs)

May 23-24: No obviously Earth directed CMEs were observed.
May 22: A faint CME, mostly over the southeast limb, but with faint traces over the southwest limb as well, was observed after the M1 flare in AR 13312. It is uncertain if there was any Earth directed component with this CME.

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 (CH1149) rotated 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 conditions are likely on May 25-26 due to effects from CH1149. Quiet conditions are expected for May 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 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
13310 2023.05.16
2023.05.17
11 24 9 S20W18 0480 CHO CHO

area: 0700

13311 2023.05.17
2023.05.18
39 61 41 N18W08 0470 EAI ESI beta-gamma-delta

location: N19W02

13312 2023.05.18
2023.05.19
15 32 19 S25E02 0050 CRO DRO

location: S25E04

13313 2023.05.18
2023.05.19
2 6 1 N22E06 0100 HSX CSO

area: 0170

13314 2023.05.19
2023.05.20
15     N12W17 0130 CSO       merged with AR 13311 on 2023.05.22

SWPC resurrected the region on 2023.05.24

see AR S8590
S8575 2023.05.19       N37W44            
S8578 2023.05.21       N17W58            
S8579 2023.05.21       S02W12            
S8580 2023.05.22   4 3 N20W27 0015   BXO  
S8582 2023.05.22       S09W16          
13315 2023.05.22
2023.05.23
11 31 18 S17E32 0130 DAI DAI beta-gamma

location: S18E33

area: 0300

S8584 2023.05.22       S19E13            
S8585 2023.05.22       N41W17            
S8586 2023.05.23   1   S28W45 0001   AXX  
S8587 2023.05.23       N25W32          
S8588 2023.05.24   9 5 S13W13 0040   DRO    
S8589 2023.05.24   6 2 S20E12 0010   AXX    
S8590 2023.05.24   24 14 N15W17 0200   DSI   beta-gamma

split off from AR 13311

S8591 2023.05.24   1   N11E50 0002   AXX    
S8592 2023.05.24   3 1 N08E63 0005   BXO    
Total spot count: 93 202 113  
Sunspot number: 153 322 213  (total spot count + 10 * number of spotted regions)
Weighted SN: 126 238 149  (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): 168 177 170  

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
2023.05 155.7 (1)   95.5 (2A) / 123.4 (2B) / 151.8 (2C) (129.3 projected, +5.6) (12.2)
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.