Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 3, 2024 at 03:10 UT. Minor update added at 14:10 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 (October 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (October 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 (October 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (October 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 levels on October 2. Solar wind speed at SOHO ranged between 345 and 417 km/sec. The high latitude magnetometer at Andenes recorded quiet to unsettled 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 274.4 - increasing 33.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 177.06. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 177.06 on April 3, 2024). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 22222111 (planetary), 22122321 (Boulder), 33122022 (Andenes).

The background x-ray flux is at the class C4 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 15 active regions using 2K resolution (SN: 441) and in 13 active regions using 1K resolution (SN: 277) SDO/HMI images.

AR 13836 [S11W47] decayed further and was quiet.
AR 13839 [S14W07] was mostly quiet and stable.
AR 13841 [N13W07] developed further before noon. Later on slow decay set in with some loss of area. The region is still complex with a significant magnetic delta configuration and could produce further M flares.
AR 13842 [S15E06] gained area and lost some small spots. There is still a magnetic delta in a trailing penumbra, however, the delta area is smaller and there is more separation between opposite polarity umbrae. A major flare is possible.
AR 13843 [S09W29] was mostly quiet and has M class flare potential.
AR 13844 [S16W16] lost the magnetic delta, however, an M flare is still possible.
AR 13845 [N17W57] decayed significantly and could soon become spotless.
AR 13846 [S09W79] decayed in the trailing spot section and was quiet.
AR 13847 [S28E47] was quiet and stable.
New AR 13848 [N13E68] rotated into view with a huge penumbra. A major flare is possible. The spot group has a magnetic delta configuration in the southern part of the huge penumbra, however, opposite polarity umbrae are at such a distance from each other that this barely classifies as a magnetic delta.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10169 [S19W28] was quiet and stable.
S10171 [S05W01] was quiet and stable.
S10186 [N16E26] was quiet and stable.
New region S10189 [N10E04] emerged with tiny spots.
New region S10190 [S20E28] was observed with tiny spots in an old plage area.

Minor update added at 14:10 UT: AR 13842 unleashed the largest flare of solar cycle 25 peaking at 12:18 UT at a magnitude of X9.05. A fast full halo CME was observed soon afterwards. The CME could reach Earth sometime between late on October 4 and noon on October 5. Expected active to very severe geomagnetic disturbance levels after the impact.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C9.2 00:23   13843 GOES16  
C8.5 01:01   13844 GOES16 simultaneous flare in AR 13841
C7.5 01:12   13842 GOES16  
C7.0 01:20   13844 GOES16  
C7.0 01:26   13841 GOES16  
C7.5 01:33   13841 GOES16  
C8.2 01:40   13843 GOES16  
M1.1 01:52   13842 GOES16  
M1.2 02:39 N12E08 13841 GOES16 simultaneous flare in AR 13842
C6.0 03:26   13842 GOES16  
C6.7 03:56 N12E08 13841 GOES16  
M1.0 05:16   13843 GOES18  
C6.9 05:21   13848 GOES18  
M3.6 05:38   13842 GOES16 small CME, moderate type II radio sweep
M1.1 06:24 N11E78 13848 GOES16 simultaneous flare in AR 13842
C6.2 06:33   13843 GOES16 simultaneous flare in AR 13842
C5.7 06:59   13835 GOES16 simultaneous flare in AR 13842
C6.0 07:05   13848 GOES16 simultaneous flare in AR 13841
C4.0 07:32   13843 GOES16 simultaneous flare in AR 13841
C4.6 08:06   13844 GOES16  
C5.1 08:12   13841 GOES16  
C5.7 09:22 S22W59 13835 GOES16  
C4.6 09:36   13842 GOES16  
C4.7 09:40   13835 GOES16  
C4.3 09:49   13841 GOES16  
C3.5 10:01   13841 GOES16  
C7.4 10:14   13844 GOES16 initially attributed to AR 13842 by SWPC
C4.1 11:18   13848 GOES16  
C4.0 12:09   13842 GOES16  
C4.5 12:23   13842 GOES16  
C4.5 13:01   13841 GOES16  
C7.4 13:11 S15W11 13844 GOES16  
M3.2/1N 13:38 S19E07 13842 GOES16  
M1.0 14:56   13841 GOES16  
C5.8 15:39   13841 GOES16  
C5.7 16:35   13842 GOES16  
C7.6 17:02   13841 GOES16  
C5.0 17:30   13843 GOES16  
C7.6 17:41 N20W56 13845 GOES16  
C5.7 17:59   13841 GOES16  
C7.1 18:30   13841 GOES16 initially attributed to AR 13843 by SWPC
C6.8 18:38   13842 GOES16  
C9.2 18:42   13842 GOES16  
C7.9 19:00   13841 GOES16  
C9.2 19:08   13843 GOES16  
C4.9 19:48   13841 GOES16  
M1.4 20:15   13842 GOES16  
M3.3 20:51   13842 GOES16  
C8.0 21:44   13835 GOES16  
C6.1 22:14   13848 GOES16  
C6.9 22:41   13841 GOES16  
C6.0 23:16   13841 GOES16  

Coronal mass ejections (CMEs)

September 30 + October 2: No obviously Earth directed CMEs observed.
October 1: A faint, full halo CME was observed after the X7.1 flare in AR 13842. The CME is likely to arrive sometime between late on October 3 and noon on October 4 and cause unsettled to severe geogmagnetic storm levels.

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 small positive polarity trans equatorial coronal hole (CH1245) will likely rotate into an Earth facing position on October 4-5.

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

The geomagnetic field is expected to be at quiet levels most of October 3. Late in the day or during the first half of October 4 the October 1 CME is likely to arrive and cause unsettled to severe storm levels.

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
13835 2024.09.22
2024.09.22
      S22W70         location: S22W67
13836 2024.09.22
2024.09.23
3 15 6 S12W48 0030 HAX CRO

location: S11W47

13845 2024.09.23
2024.10.01
6 2 1 N19W60 0010 BXO HRX location: N17W57
13838 2024.09.24
2024.09.26
      N15W40           location: N16W38
S10160 2024.09.25       S03W52          
13840 2024.09.25
2024.09.27
      N14W56           location: N12W54
13841 2024.09.25
2024.09.28
17 54 31 N13W08 0220 DAI DAC beta-gamma-delta

location: N13W07

area: 0420

13839 2024.09.26
2024.09.26
2 13 6 S15W08 0060 CSO CSO

area: 0120

location: S14W07

S10165 2024.09.26       S38W50            
13842 2024.09.27
2024.09.28
27 69 32 S15E06 0380 EKC EKC beta-gamma-delta

area: 1010

S10169 2024.09.27   10 2 S19W28 0020   AXX  
S10170 2024.09.27       N25W30            
S10171 2024.09.27   6 1 S05W01 0012   BXO  
S10172 2024.09.27       S03W31            
13843 2024.09.28
2024.09.29
17 38 22 S09W25 0180 DAI DAI

location: S09W29

area: 0410

S10176 2024.09.28       N17E27            
S10177 2024.09.28       N16W23          
S10178 2024.09.28       S14E09            
13844 2024.09.29
2024.09.30
11 51 27 S15W16 0160 DAI DAC

location: S16W16

area: 0330

S10180 2024.09.29       N01E06            
13846 2024.09.30
2024.10.01
5 4 3 S09W65 0020 CRO CAO location: S09W79

area: 0060

SWPC location is way off

S10182 2024.09.30       S07E28          
13847 2024.09.30
2024.10.01
1 2 2 S28E45 0020 HRX HAX area: 0040

location: S28E47

S10184 2024.09.30       N28W08            
13848 2024.10.01
2024.10.02
5 18 13 N14E70 0280 DHC DKC beta-delta

location: N13E68

area: 1200

S10186 2024.10.01   1   N16E26 0003   AXX  
S10187 2024.10.01       N34W17          
S10188 2024.10.01       S34E05          
S10189 2024.10.02   2 1 N10E04 0005   BXO    
S10190 2024.10.02   6   S20E28 0010   BXO    
Total spot count: 94 291 147  
Sunspot number: 194 441 277  (total spot count + 10 * number of spotted regions)
Weighted SN: 145 347 203  (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): 213 243 222  

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
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
2024.03 154.4 152.9 103.7 141.3 (+4.5) 11.03
2024.04 161.3 162.6 136.5 (145.3 projected, +4.0) 9.69
2024.05 187.7 191.9 171.7 (151.6 projected, +6.3) 23.56
(SC25 peak)
2024.06 184.3 190.2 164.2 (155.5 projected, +3.9) 10.24
2024.07 196.6
 
203.0 196.5  (158.4 projected, +2.9) 7.13
2024.08  246.1
(cycle peak)
252.2 215.5  (SC25 peak) (160.4 projected, +2.0) 15.96
2024.09 195.7 197.8 141.4 (163.1 projected, +2.7) 15.3
2024.10 259.5 (1)   12.6 (2A) / 195 (2B) / 194.4 (2C) (165.4 projected, +2.3) (5.5)
2024.11       (163.7 projected, -1.7)  
2024.12       (160.7 projected, -3.0)  
2025.01       (156.3 projected, -4.4)  
2025.02       (149.6 projected, -6.7)  
2025.03       (144.8 projected, -4.8)  
2025.04       (141.6 projected, -3.2)  

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.