Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 20, 2023 at 08:00 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 active on May 19. Solar wind speed at SOHO ranged between 307 and 390 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. Solar wind speed increased slowly after 18h UT at DSCOVR and a corotating interaction region associated with CH1148 caused increasing geomagnetic activity after 21h. The disturbance intensified early on May 20 when major storming was recorded.

Solar flux density measured at 20h UT on 2.8 GHz was 164.6 - increasing 23.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 140.73. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.6). Three hour interval K indices: 11111224 (planetary), ******** (Boulder), 00101445 (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 13 active regions using 2K resolution (SN: 305) and in 10 active regions using 1K resolution (SN: 188) SDO/HMI images.

Region 13302 [N17W57] decayed slowly and quietly.
Region 13305 [N11W55] produced a few low level flares and appeared to be consolidating. A minor M class flare is possible.
Region 13308 [N11W40] still has minor polarity intermixing and decayed in the leading spot section.
Region 13309 [S18W76] decayed slowly and was mostly quiet.
Region 13310 [S21E48] displayed only minor changes and was mostly quiet. An M class flare is possible.
Region 13311 [N18E61] continued to be very active producing many C and M flares. The region is complex and compact with polarity intermixing and magnetic deltas. Major flares are possible. C1 flares: C1.8 @ 11:52 UT
New region 13312 [S24E70] rotated partly into view on May 18 and was numbered by SWPC the next day. A few C flares were recorded. The region appears to be in slow decay.
New region 13313 [N21E76] rotated into view with a large, mature spot.

Spotted regions not observed (or interpreted differently) by SWPC:
S8569 [S30E03] was quiet and stable.
New region S8573 [N14E50] emerged with several small spots.
New region S8574 [N24E08] was observed with tiny spots in an old plage area.
New region S8575 [N35E27] emerged with tiny spots.
New region S8576 [S22W30] was observed with tiny spots in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C5.1 00:15   13310 GOES16 simultaneous flare in AR 13311
M5.3/1N 00:48 N18E74 13311 GOES16  
C2.6 02:04   13312 GOES16  
C2.9 02:16   13308 GOES16  
C2.6 02:33   13309 GOES16  
C6.9 02:58 N19E72 13311 GOES16  
M1.6 03:12 N19E72 13311 GOES16  
C2.9 04:45 N19E72 13311 GOES16  
M2.5/1N 05:00 N19E72 13311 GOES16  
C3.9 05:39   13310 GOES16 simultaneous flare in AR 13311
C3.1 06:07   13311 GOES16  
C3.2 06:31 N19E72 13311 GOES16 simultaneous flare in AR 13309
C5.7 06:49   13311 GOES16  
C4.0 07:10   13311 GOES16 simultaneous flare in AR 13305
C4.7 07:42   13311 GOES16 simultaneous flare in AR 13305
C2.8 09:30 N18E70 13311 GOES16  
C4.0 10:17 N18E70 13311 GOES16  
C6.1 12:39 N16E65 13311 GOES16  
C2.9 15:35   13311 GOES16 simultaneous flare in AR 13305
C2.6 15:54   13311 GOES16  
C5.9 16:31   13311 GOES16  
C4.1 17:21   13311 GOES16  
C5.3 17:29   13311 GOES16  
C2.0 18:52   13311 GOES16  
C5.1 19:14   13312 GOES16  
C3.2 19:43   13311 GOES16  
M2.3 20:06 N16E61 13311 GOES16  
M2.7 20:26   13311 GOES16  
M1.5 21:14   13311 GOES16  
C3.3 22:48   13312 GOES16 simultaneous flare in AR 13311
C2.1 23:34   13311 GOES16  

Coronal mass ejections (CMEs)

May 18-19: No obviously Earth directed CMEs were observed.
May 17: A filament eruption associated with a C4 flare in AR 13309 was the source of a CME that may have Earth directed components. If that's the case weak effects could reach Earth on May 20 or 21.

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 likely 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 major storm is expected for May 20 due to effects related to CH1148. Quiet to unsettled 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
13303 2023.05.07
2023.05.09
      S10W83           location: S12W74
13301 2023.05.08
2023.05.09
      N14W65        

location: N14W62

13304 2023.05.08
2023.05.11
      N20W89            
13302 2023.05.08
2023.05.09
1 1 1 N18W58 0050 HSX HSX area: 0080

location: N17W57

13305 2023.05.12 18 28 18 N12W57 0240 DAI DAI

location: N11W55

area: 0320

S8558 2023.05.13       S37W46            
S8560 2023.05.14       S28W54            
13308 2023.05.14
2023.05.16
15 32 18 N12W41 0070 CAO DRI

location: N11W40

area: 0120

13307 2023.05.14
2023.05.15
1     S09W20 0010 AXX    

spotless

location: S10W18

S8565 2023.05.14       S21W35            
S8566 2023.05.15       N21W11            
13309 2023.05.16
2023.05.17
3 6 3 S18W77 0010 BXO BXO area: 0030

location: S18W76

13310 2023.05.16
2023.05.17
8 14 7 S20E48 0320 CKO CKO location: S21E48

area: 0580

S8569 2023.05.16   4   S30E03 0004   BXO  
13311 2023.05.17
2023.05.18
12 47 25 N17E60 0330 EKC EAC beta-delta

location: N18E61

area: 0550

13312 2023.05.18
2023.05.19
6 24 8 S25E70 0040 CRO DRI area: 0100

location: S24E70

13313 2023.05.18
2023.05.19
1 1 1 N22E75 0030 HSX HSX   was AR S8572

location: N21E76

area: 0230

S8573 2023.05.19   7 5 N14E50 0020   DRO    
S8574 2023.05.19   6   N24E08 0008   BXO    
S8575 2023.05.19   2 2 N35E27 0007   BXO    
S8576 2023.05.19   3   S22W30 0005   BXO    
Total spot count: 65 175 88  
Sunspot number: 155 305 188  (total spot count + 10 * number of spotted regions)
Weighted SN: 108 214 127  (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): 171 168 150  

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
2023.05 154.1 (1)   74.3 (2A) / 121.2 (2B) / 146.9 (2C) (129.3 projected, +5.6) (9.9)
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.