Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 18, 2023 at 08:35 UT covering May 16 data. The update for May 17 will be posted later today.

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 16 under the influence of weak effects from CH1147. Solar wind speed at SOHO ranged between 428 and 504 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 134.3 - decreasing 13.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 140.93. 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: 6.8). Three hour interval K indices: 22311112 (planetary), 33312312 (Boulder), 55112234 (Andenes).

The background x-ray flux is at the class B9 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 13 active regions using 2K resolution (SN: 262) and in 11 active regions using 1K resolution (SN: 172) SDO/HMI images.

Region 13301 [N14W22] decayed slowly losing all mature penumbra. C1 flares: C1.0 @ 05:46 UT
Region 13302 [N18W17] decayed slowly and quietly.
Region 13304 [N19W49] decayed slowly and quietly.
Region 13305 [N10W13] produced low level C flares. An M flare is possible. C1 flares: C1.1 @ 00:53, C1.3 @ 04:31, C1.0 @ 06:22, C1.5 @ 20:10, C1.9 @ 21:49 UT
Region 13306 [S18W62] decayed slowly and was quietly.
Region 13307 [S09E18] decayed slowly and quietly.
New region 13308 [N11E01] emerged on May 14 and was numbered by SWPC 2 days later as the region developed slowly.

Spotted regions not observed (or interpreted differently) by SWPC:
S8549 [S21W22] was quiet and stable.
S8555 [S24W49] reemerged with a tiny spot.
S8565 [S21E05] reemerged with tiny spots.
New region S8567 [S18W39] emerged with several spots.
New region S8568 [S21E85] rotated partly into view with a large leader spot. Further major flares are possible. C1. flares: C1.2 @ 04:44, C1.5 @ 13:43, C1.1 @ 15:42,  C1.0 @ 19:36 UT
New region S8569 [S29E40] emerged with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.0 09:54   S8568 GOES16  
C4.5 12:14   S8568 GOES16  
C2.4 12:55   S8568 GOES16  
M9.6 16:43   S8568 GOES16  
C2.3 22:42   S8568 GOES16  

Coronal mass ejections (CMEs)

May 14-16: 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 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 21-23.

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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

Mostly quiet geomagnetic conditions are expected on May 17-18. 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
      S10W41         location: S12W35
13301 2023.05.08
2023.05.09
6 13 9 N14W27 0030 HSX HRX

location: N14W22

13304 2023.05.08
2023.05.11
2 4 1 N20W47 0010 AXX AXX location: N19W49

area: 0006

13302 2023.05.08
2023.05.09
4 11 5 N18W22 0050 HSX CSO area: 0100

location: N18W17

S8549 2023.05.09   7 1 S21W22 0012   BXO  
S8551 2023.05.10       N13W45            
13306 2023.05.10
2023.05.14
2 3 1 S18W64 0010 AXX CRO location: S18W62
13305 2023.05.12 18 63 29 N09W16 0100 DAI DAI

location: N10W13

area: 0250

S8555 2023.05.12   1   S24W49 0001   AXX    
S8556 2023.05.12       N13W59            
S8557 2023.05.13       N25W49            
S8558 2023.05.13       S37E06            
S8559 2023.05.14       N27W50            
S8560 2023.05.14       S28W02            
13308 2023.05.14
2023.05.16
2 9 7 N12W00 0010 BXO CRO location: N11E01

area: 0040

13307 2023.05.14
2023.05.15
2 7 1 S08E22 0010 AXX CRO

location: S09E18

S8564 2023.05.14       S22W46            
S8565 2023.05.14   2 2 S21E05 0011   BXO    
S8566 2023.05.15       N21E28          
S8567 2023.05.16   10 5 S18W39 0040   DRO    
S8568 2023.05.16   1 1 S21E85 0300   HKX    
S8569 2023.05.16   1   S29E40 0003   AXX    
Total spot count: 36 132 62  
Sunspot number: 106 262 172  (total spot count + 10 * number of spotted regions)
Weighted SN: 49 167 97  (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): 117 144 138  

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
2023.05 154.6 (1)   62.0 (2A) / 120.1 (2B) / 148.9 (2C) (129.3 projected, +5.6) (11.1)
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.