Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 18, 2023 at 12:50 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 very quiet on May 17. Solar wind speed at SOHO ranged between 372 and 396 km/sec. The high latitude magnetometer at Andenes recorded quiet to unsettled levels.

Solar flux density measured at 20h UT on 2.8 GHz was 137.9 - decreasing 9.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 140.83. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.0). Three hour interval K indices: 11011110 (planetary), 11012323 (Boulder), 31011111 (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 10 active regions using 2K resolution (SN: 203) and in 8 active regions using 1K resolution (SN: 127) SDO/HMI images.

Region 13301 [N14W36] decayed slowly and quietly.
Region 13302 [N18W31] decayed slowly and quietly.
Region 13305 [N11W29] decayed in the southern spot sections and was mostly quiet. C1 flares: C1.7 @ 01:56, C1.1 @ 04:43 UT
Region 13307 [S10E07] was quiet and stable.
Region 13308 [N11W13] developed slowly and quietly.
New region 13309 [S18W51] emerged on May 16 and decayed slowly on May 17 when it was numbered by SWPC.
New region 13310 [S21E75] rotated partly into view on May 16 and was numbered the following day by SWPC. The region is compact and could produce another major flare. C1 flares: C1.5 @ 09:35, C1.3 @ 10:59, C1.4 @ 12:33, C1.3 @ 12:59, C1.5 @ 13:35 UT

Spotted regions not observed (or interpreted differently) by SWPC:
S8565 [S21W09] decayed slowly and quietly.
S8569 [S29E28] developed slowly and quietly.
New region S8570 [N16E86] rotated partly into view and is capable of major flaring. The region is very active and has produced several M flare on May 18.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.9 03:48   13310 GOES16  
C2.1 07:58   13310 GOES16  
C2.3 08:28   13310 GOES16  
C6.4 14:43   S8570 GOES16  
C4.3 15:30   13309 GOES16 moderate type II radio sweep, CME. Flare triggered a filament eruption
C7.4 16:28   S8570 GOES16  
C3.6 16:53   13310 GOES16  
C3.3 17:36   S8570 GOES16  
C2.7 17:59   13310 GOES16  
C6.2 18:44   S8570 GOES16  
C5.0 19:38   S8570 GOES16  
C9.5 21:48   S8570 GOES16  

Coronal mass ejections (CMEs)

May 15-16: 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

Mostly quiet geomagnetic conditions are expected on May 18. On May 19-20 effects from CH1148 could cause quiet to minor storm conditions.

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
      S10W55           location: S12W48
13301 2023.05.08
2023.05.09
4 9 5 N15W37 0010 AXX HRX

location: N14W36

13304 2023.05.08
2023.05.11
      N20W61         location: N19W62
13302 2023.05.08
2023.05.09
1 2 1 N18W33 0050 HSX CAO area: 0100

location: N18W33

S8549 2023.05.09       S21W35          
S8551 2023.05.10       N13W58            
13306 2023.05.10
2023.05.14
      S18W78         location: S18W75
13305 2023.05.12 19 40 19 N12W30 0110 DAI DAO

location: N11W29

area: 0140

S8558 2023.05.13       S37W07            
S8560 2023.05.14       S28W15            
13308 2023.05.14
2023.05.16
4 19 8 N12W14 0020 CRO DRI location: N11W13

area: 0040

13307 2023.05.14
2023.05.15
1 10 4 S08E03 0010 AXX BXO

location: S10E07

area: 0020

S8564 2023.05.14       S22W59            
S8565 2023.05.14   2   S21W09 0003   BXO  
S8566 2023.05.15       N21E15            
13309 2023.05.16
2023.05.17
4 4 2 S18W53 0020 CRO BXO  
13310 2023.05.16
2023.05.17
3 11 6 S20E74 0250 DHO DKC  
S8569 2023.05.16   4 2 S29E28 0012   CRO  
S8570 2023.05.17   2   N16E86 0050   CAO    
Total spot count: 36 103 47  
Sunspot number: 106 203 127  (total spot count + 10 * number of spotted regions)
Weighted SN: 62 137 81  (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): 117 112 102  

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
2023.05 153.6 (1)   65.4 (2A) / 119.2 (2B) / 147.1 (2C) (129.3 projected, +5.6) (10.6)
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.