Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 28, 2023 at 06:55 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 (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 on May 27. Solar wind speed at SOHO ranged between 427 and 539 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 156.9 - increasing 3.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 141.00. 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: 3.6). Three hour interval K indices: 11110012 (planetary), 12122322 (Boulder), 21111234 (Andenes).

The background x-ray flux is at the class B8 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 14 active regions using 2K resolution (SN: 315) and in 11 active regions using 1K resolution (SN: 206) SDO/HMI images.

Region 13310 [S20W58] was quiet and stable.
Region 13311 [N19W42] gained a few intermediate and trailing spots. The region has polarity intermixing and may still be capable of M class flaring. C1 flares: C1.9 @ 16:22 UT
Region 13312 [S24W34] was mostly quiet and stable. C1 flares: C1.1 @08:59 UT
Region 13313 [N22W27] was quiet and stable.
Region 13315 [S17W07] gained area, however, opposite polarity fields are separating. The magnetic delta observed the previous day disappeared. M class flaring is possible. C1 flares: C1.2 @ 00:31, C1.0 @ 01:59, C1.1 @ 04:25, C1.1 @ 06:40, C1.0 @ 09:30, C1.0 @ 11:20, C1.2 @ 13:16, C1.6 @ 16:36, C1.3 @ 18:17, C1.2 @ 20:24, C1.3 @ 20:40, C1.5 @ 22:38 UT
Region 13316 [N08E23] developed slowly and was mostly quiet. C1 flares: C1.3 @ 12:51, C1.4 @ 21:23 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8589 [S20W25] was quiet and stable.
S8590 [N16W58] is a compact region with a magnetic delta configuration and M class flaring potential.
S8595 [N19E20] was quiet and stable.
New region S8596 [N01E09] emerged before noon, then decayed slowly.
New region S8597 [N24W08] emerged with tiny spots.
New region S8598 [S09E14] emerged with tiny spots.
New region S8599 [S19E27] emerged with a few spots.
New region S8600 [S14E36] was observed with tiny spots in an old plage area.

A C1.1 flare at 12:11 UT had its origin behind the southeast limb.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C8.4 04:35   13311 GOES16 moderate type II radio sweep
flare was in the leading spot section of AR 13311
C2.8 06:12   13315 GOES16  
C2.1 14:48 S17W02 13315 GOES16  
C2.9 15:27   13311 GOES16  
C3.3 15:52   13315 GOES16  
C6.2 19:24   13312 GOES16 weak type II radio sweep
C2.2 21:53   13315 GOES16  

Coronal mass ejections (CMEs)

May 25-27: 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 likely rotate across the central meridian on May 31 - June 1.

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 28-30.

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
1 10 6 S20W58 0260 HHX CHO

area: 0480

13311 2023.05.17
2023.05.18
8 33 17 N18W46 0180 EAO ESI

location: N19W42

13312 2023.05.18
2023.05.19
6 23 15 S25W36 0020 BXO BXI

location: S24W34

area: 0040

13313 2023.05.18
2023.05.19
1 4 1 N23W28 0100 HSX CSO

area: 0150

location: N22W27

13314 2023.05.19
2023.05.20
4     N15W58 0120 DAO       merged with AR 13311 on 2023.05.22

SWPC resurrected the region on 2023.05.24

see AR S8590
S8579 2023.05.21       S02W51            
S8582 2023.05.22       S09W47            
13315 2023.05.22
2023.05.23
28 45 31 S17W08 0620 EKC EKC beta-gamma-delta

location: S17W07

area: 0940

S8584 2023.05.22       S19W26            
S8588 2023.05.24       S12W55          
S8589 2023.05.24   3   S20W25 0004   AXX  
S8590 2023.05.24   14 8 N16W58 0160   DAC beta-delta
S8591 2023.05.24       N12E14            
13316 2023.05.24
2023.05.26
7 19 9 N09E22 0030 CRO DRI area: 0070

location: N08E23

S8593 2023.05.25       N26W13            
S8594 2023.05.26       N08E07          
S8595 2023.05.26   4   N19E20 0006   BXO  
S8596 2023.05.27   2   N01E09 0002   BXO    
S8597 2023.05.27   6 2 N24W08 0025   CRO    
S8598 2023.05.27   3 2 S09E14 0008   BXO    
S8599 2023.05.27   5 3 S19E27 0020   CRO    
S8600 2023.05.27   4 2 S14E36 0007   BXO    
Total spot count: 55 175 96  
Sunspot number: 125 315 206  (total spot count + 10 * number of spotted regions)
Weighted SN: 93 219 140  (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): 138 173 165  

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)   107.5 (2A) / 123.5 (2B) / 153.0 (2C) (129.3 projected, +5.6) (11.6)
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.