Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 24, 2024 at 09:10 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 (September 1, 2024)
Solar cycle Solar cycles 23-25 (September 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (September 1, 2024) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (August 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (September 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (September 1, 2024) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (June 17, 2024) 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
Calculating the Strength of Solar Cycle 25 Using 365-day Smoothing

Recent activity

The geomagnetic field was at quiet to active levels on September 23. The brief disturbance appears to have been caused by a solar wind transient, likely a CME. Solar wind speed at SOHO ranged between 372 and 480 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at background levels at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 167.4 - decreasing 53.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 175.92. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 176.05 on March 21, 2024). The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 11.6). Three hour interval K indices: 11234421 (planetary), 11233421 (Boulder), 30124522 (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 14 active regions using 2K resolution (SN: 276) and in 14 active regions using 1K resolution (SN: 206) SDO/HMI images.

AR 13827 [S26W31] was quiet and stable.
AR 13828 [S11W20] was mostly quiet and stable.
AR 13831 [N13W49] decayed slowly and was mostly quiet. C1 flares: C1.9 @ 02:59 UT
AR 13833 [N21W39] merged with AR S10145 and has a magnetic delta configuration even though none of the spots have mature penumbra. C1 flares: C1.6 @ 09:27 UT
AR 13834 [S14E27] was quiet and stable.
AR 13835 [S23E49] developed further gaining area.
New AR 13836 [S10E72] rotated partly into view on September 22 and was numbered the next day by SWPC. The region is compact and could produce further M class flares.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10135 [S18W66] decayed slowly and quietly.
S10144 [N12E03] was quiet and stable.
S10148 [S21E42] was mostly quiet and stable.
New region S10150 [S11E09] emerged with several spots.
New region S10151 [S21E52] emerged with a few spots.
New region S10152 [N22E67] emerged with tiny spots.
New region S10153 [N03W09] was observed with spots in an old plage area.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.3 03:46   13836 GOES16  
C2.5 04:11   S10148 GOES16  
C2.3 05:50   13828 GOES16  
C4.5 10:06   13825 GOES16  
C2.3 13:59   13836 GOES16  
M1.3 14:55   13836 GOES16  
M1.2 15:07   13833 GOES16  
C3.4 17:16 S10W15 13828 GOES16  
C3.2 17:30   13828 GOES16  

Coronal mass ejections (CMEs)

September 21, 23: No obviously Earth directed CMEs observed.
September 22: A CME was observed after the M flare in AR 13835. While the main ejecta will not reach Earth, a solar wind shock is possible on September 26.

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 positive polarity trans equatorial coronal hole (CH1243) was in an Earth facing position on September 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. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be at quiet to unsettled levels on September 24-25 due to effects from CH1243. The September 22 CME could reach Earth on September 25 or 26 and cause unsettled to minor storm conditions.

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
13825 2024.09.12
2024.09.13
1     S17W75 0080 HSX    

area: 0008

location: S15W76

there are no spots near the location reported by SWPC. They are probably including AR S10135, however that spot is at S18W66

S10123 2024.09.15       S09W47          
13832 2024.09.15
2024.09.20
      N13W87        

location: N13W85

13827 2024.09.15
2024.09.16
3 6 2 S26W35 0120 CAO CAO location: S26W31

area: 0130

S10127 2024.09.15       N08W42            
13828 2024.09.16
2024.09.16
20 28 11 S12W23 0180 DKO CKO

area: 0350

location: S11W20

SWPC classification and area are incompatible

S10135 2024.09.18   1 1 S18W66 0050   HSX  
13833 2024.09.18
2024.09.20
10 17 9 N22W44 0060 DAO DRI beta-delta

location: N21W39

SWPC location is way off

13831 2024.09.19
2024.09.19
3 9 5 N14W51 0080 CAO DAO

location: N13W49

area: 0120

S10139 2024.09.19       S29W54            
13834 2024.09.19
2024.09.20
4 13 7 S16E23 0040 CAO CAO area: 0180

location: S14E27

S10142 2024.09.19       S10W28            
S10144 2024.09.20   9 3 N12E03 0020   BXO  
S10145 2024.09.21       N22W36         merged with AR 13833 on 2024.09.23
S10146 2024.09.21       N31W16            
S10147 2024.09.21       N10W21          
S10148 2024.09.21   2 2 S21E42 0004   BXO  
13835 2024.09.22
2024.09.22
3 9 5 S25E49 0050 DSO DAO location: S23E49

area: 0080

13836 2024.09.22
2024.09.23
10 20 11 S12E72 0080 DSI DAC beta-gamma

area: 0300

location: S10E72

SWPC reports this with 100 spots, however, that is a typo

S10150 2024.09.23   5 3 S11E09 0025   CRO    
S10151 2024.09.23   5 3 S21E52 0070   DAO   beta-delta
S10152 2024.09.23   2 1 N22E67 0004   AXX    
S10153 2024.09.23   10 3 N03W09 0015   AXX    
Total spot count: 54 136 66  
Sunspot number: 134 276 206  (total spot count + 10 * number of spotted regions)
Weighted SN: 99 187 117  (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): 147 152 165  

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
2022.12 147.9 143.4 112.8 106.7 (+5.5) 10.99
2023.01 182.4 176.6 144.4 113.3 (+6.6) 8.73
2023.02 167.2 163.2 111.3 117.8 (+3.5) 14.48
2023.03 157.2 155.6 123.3 121.1 (+3.3) 14.42
2023.04 145.4 146.4 97.6 122.9 (+1.8) 13.40
2023.05 155.6 159.2 137.4 124.2 (+1.3) 10.67
2023.06 161.7 166.8 160.5 125.3 (+1.1) 8.95
2023.07  176.4 182.2 160.0 124.6 (-0.7) 8.15
2023.08  153.7 157.6 114.8 124.3 (-0.3) 7.19
2023.09  154.4 156.0 134.2 124.0 (-0.3) 14.26
2023.10  142.8 141.9 99.4 124.8 (+0.8) 8.16
2023.11 153.5 150.2 105.4 127.8 (+3.0) 12.20
2023.12 151.1 146.4 114.2 129.4 (+1.6) 9.60
2024.01 164.6 159.3 126.0 131.1 (+1.7) 5.46
2024.02 172.5 168.3 123.0 136.8 (+5.7) 5.31
2024.03 154.4 152.9 103.7 (143.3 projected, +6.5) 11.03
2024.04 161.3 162.6 136.5 (147.8 projected, +4.5) 9.69
2024.05 187.7 191.9 171.7 (152.6 projected, +4.8) 23.56
(SC25 peak)
2024.06 184.3 190.2 164.2 (156.5 projected, +4.0) 10.24
2024.07 196.6
 
203.0 196.5  (158.3 projected, +1.8) 7.13
2024.08  246.1
(cycle peak)
252.2 215.5  (SC25 peak) (158.7 projected, +0.4) 15.96
2024.09 197.8 (1)   110.0 (2A) / 143.5 (2B) / 183.8 (2C)
[ISN average: 148]
(160.8 projected, +2.1) (16.2)
2024.10       (162.7 projected, +1.9)  
2024.11       (160.7 projected, -2.0)  
2024.12       (156.4 projected, -4.3)  
2025.01       (150.3 projected, -6.1)  
2025.02       (143.0 projected, -7.3)  
2025.03       (136.2 projected, -6.8)  

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 September 7, 2024

Sunspot counts in August 2024 were much higher than during any previous solar cycle 25 month. In comparison only 3 months during solar cycle 23 had higher SSN. Sunspot counts in early September are still high, although lower than in the beginning of August. With at least 5 consecutive months of high sunspot counts the projected peak for the smoothed ISN (365 days smoothing) has increased significantly to above 160 and could easily surpass 170 if the current activity lasts through October. The month of the peak is likely to occur sometime between July and November 2024.

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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.