Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 29, 2023 at 09:20 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 (August 5, 2023)
Solar cycle Solar cycles 23-25 (August 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (August 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 (August 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (August 1, 2023) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (July 10, 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 August 27. Solar wind speed at SOHO ranged between 312 and 399 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 141.4 - decreasing 35.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 153.25. 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: 9.5). Three hour interval K indices: 43211221 (planetary), 44412331 (Boulder), 55123344 (Andenes).

The background x-ray flux is at the class B6 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 227) and in 7 active regions using 1K resolution (SN: 103) SDO/HMI images.

Region 13411 [N13W81] was quiet and stable.
Region 13412 [N30W43] was quiet and stable.
Region 13413 [N09W10] was quiet and decayed slowly.
Region 13414 [S14W36] was quiet and stable.
Region 13415 [S10E09] decayed slowly as the magnetic delta weakened.
Region 13416 [S19E42] was quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S8896 [N28E28] was quiet and stable.
S8897 [N16E15] was quiet and stable.
S8898 [S18E17] was quiet and stable.
S8899 [S17W18] decayed slowly and quietly.
New region S8900 [N12E44] was observed with tiny spots in an old plage area.
New region S8901 [S11E32] was observed with tiny spots in an old plage area.

An active region is rotating into view at S06 early on August 28.. This region was the likely source of the M1.1 LDE peaking at 22.50 UT on August 26.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.6 03:04 behind NW limb 13405 GOES16  

Coronal mass ejections (CMEs)

August 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 southern hemisphere coronal hole (CH1166) rotated across the central meridian on August 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. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet on August 28-30.

Coronal holes (1) Coronal mass ejections (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
13411 2023.08.15
2023.08.17
1 1 1 N14W84 0040 HSX HSX

area: 0070

location: N13W81

13412 2023.08.17
2023.08.18
1 1 1 N31W47 0060 HSX HSX area: 0080

location: N30W43

13414 2023.08.18
2023.08.21
  6   S10W51 0010   AXX location: S14W36
13413 2023.08.20
2023.08.21
12 39 15 N10W13 0260 DKI CKI

area: 0520

location: N09W10

13415 2023.08.22
2023.08.22
4 23 10 S10E06 0200 DAO DKC  

beta-delta

location: S10E09

area: 0310

S8888 2023.08.22       N14E01            
S8889 2023.08.22       N21W41          
S8890 2023.08.23       S03W41            
13416 2023.08.24
2023.08.25
1 3 1 S19E38 0050 HSX CSO area: 0080

location: S19E42

S8893 2023.08.24       S22E30            
S8894 2023.08.24       N20E11            
S8896 2023.08.26   12 1 N28E28 0020   BXO  
S8897 2023.08.26   11 4 N16E15 0020   BXO  
S8898 2023.08.26   3   S18E17 0005   BXO  
S8899 2023.08.26   2   S17W18 0003   AXX  
S8900 2023.08.27   2   N12E44 0003   AXX    
S8901 2023.08.27   4   S11E32 0003   AXX    
Total spot count: 19 107 33  
Sunspot number: 69 227 103  (total spot count + 10 * number of spotted regions)
Weighted SN: 49 142 68  (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): 76 125 82  

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
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 80.5 101.0 (+2.3) 9.33
2022.12 147.9 143.4 112.8 106.6 (+5.6) 10.99
2023.01 182.4 176.6 143.6 113.3 (+6.7) 8.73
2023.02 167.2 163.2 110.9 (119.1 projected, +5.8) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 122.6 (124.4 projected, +5.3) 14.42
2023.04 145.4 146.4 96.4 (130.5 projected, +6.1) 13.40
2023.05 155.6 159.2 137.9 (136.1 projected, +5.6) 10.67
2023.06 161.7 166.8 163.4 (139.3 projected, +3.2) 8.95
2023.07  176.4 182.2 159.1 (139.7 projected, +0.4) 8.15
2023.08  155.6 (1)   89.1 (2A) / 102.3 (2B) / 127.9 (2C) (141.5 projected, +1.8) (7.6)
2023.09       (145.0 projected, +3.5)  
2023.10       (146.8 projected, +1.8)  
2023.11       (149.4 projected max SC25, +2.6)  
2023.12       (148.6 projected, -0.8)  
2024.01       (145.7 projected, -2.9)  
2024.02       (144.3 projected, -1.4)  

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: WDC-SILSO, Royal Observatory Of Belgium, Brussels

Solar cycles 24-25

Smoothed SF and sunspot numbers

Update on the progress of solar cycle 25 as of August 20, 2023

Looking back 6 months, the 365d smoothed values for solar flux and all sunspot numbers with the exception of NOAA's, are all above their solar cycle 24 peak. The first peak of solar cycle 25 is projected to be between July 7 and 10, 2023 (solar flux on July 7, ISN and STAR 1K and 2K all have that peak on July 9, while NOAA peaks on July 10). This is unlikely to be the final peak of SC25, there is only a small chance that it is the actual sunspot and solar flux maximum.

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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.