Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 17, 2026 at 08:45 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 (October 11, 2026)
Solar cycle Solar cycles 23-25 (October 1, 2026) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (October 1, 2026) 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, 2026) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (October 1, 2026) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (December 21, 2025) Cycle 25 initial spots (final update December 25, 2019)
  Solar cycles 24-25 transition using 365d smoothing  

Recent activity

The geomagnetic field was at quiet to active levels under the influence of effects associated with CH1404. Solar wind speed at SOHO ranged between 470 and 516 km/sec, averaging 495 km/sec (-17 km/sec compared to the previous day). The high latitude magnetometer at Andenes was at quiet to major storm levels. The above 10 MeV proton flux was at background levels all day.

Solar flux density measured at 20h UT on 2.8 GHz was 131.2 - increasing 34.1 over the previous solar rotation.

The 365 day average solar flux at 1 AU was 131.46 (183 days ago). The 81 day average solar flux at 1 AU was 114.6 (41 days ago, this is 28.8% of the total SC25 solar flux range from the max 81 day average peak on September 4, 2024 at 227.3 and an average 81 day flux of 69 at solar minimum). SC25 365d peak: 195.9 on October 13, 2024.

The Potsdam WDC planetary A index was 11 (STAR Ap - based on the average of three hour interval ap indices: 11.4). Three hour interval K indices: 31122342 (planetary), 32223332 (Boulder), 32122465 (Andenes).

The background x-ray flux is at the class B6 level (GOES 19).

At the time of counting spots (see image time), spots were observed in 7 active regions using 2K resolution (SN: 187) and in 6 active regions using 1K resolution (SN: 125) SDO/HMI images.

AR 14551 [S13W20] lost the magnetic delta and still has significant polarity intermixing. Further M flares are possible. C1 flares: C1.8 @ 01:41, C1.6 @ 03:34, C1.7 @ 04:30, C1.8 @ 04:37, C1.7 @ 04:42, C1.1 @ 05:05, C1.3 @ 06:22, C1.0 @ 06:38, C1.5 @ 10:54, C1.1 @ 15:26, C1.0 @ 17:51, C1.3 @ 18:06, C1.6 @ 18:14, C1.5 @ 18:38, C1.3 @ 18:58, C1.5 @ 19:41, C1.0 @ 19:55, C1.5 @ 21:10, C1.2 @ 22:32 UT
AR 14553 [N08W06] was mostly quiet and stable. C1 flares: C1.4 @ 11:08 UT
AR 14555 [S07W68] decayed slowly and quietly.
AR 14556 [N03E18] was quiet and stable.
AR 14557 [N07E14] gained spots and area and has minor polarity intermixing. An M flare is possible. C1 flares: C1.1 @ 02:54, C1.0 @ 03:03, C1.9 @ 12:54, C1.1 @ 15:16, C1.0 @ 23:06 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
New AR S12420 [S19W11] emerged with tiny spots to the southeast of AR 14551. C1 flares: C1.5 @ 18:44 UT
New AR S12421 [N19E05] emerged with a tiny spot.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C3.1 00:19 S10W09 14551 GOES18  
C3.0 01:17   14551 GOES18 simultaneous flare in AR 14557
C2.0 11:55   14553 GOES18  
C2.0 12:33   14551 GOES18  
C2.0 12:41   S12420 GOES18  
M1.3/1N 15:42   14551 GOES18  
C2.1 19:06 S14W15 14551 GOES18  
C6.0 19:14   14551 GOES18  

Coronal mass ejections (CMEs)

October 15-16: No obviously Earth directed CMEs were observed.
October 14: An extensive filament eruption, mainly in the northeast quadrant, was observed before noon. The associated CME could have Earth directed components.

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 southern hemisphere coronal hole (CH1405) will rotate across the central meridian on October 16-17. A recurrent negative polarity northern hemisphere coronal hole (CH1406) will likely become Earth facing on October 19-20.

Forecast

The geomagnetic field is expected to be at quiet levels on October 17-18, however, components of the October 14 CME could reach Earth and cause unsettled to minor storm levels. Quiet to minor storm levels are possible on October 19-20 due to effects associated with CH1405.

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
STAR SWPC STAR Current Previous
2K 1K
14551 2026.10.08
2026.10.09
34 53 33 S14W19 0600 EKI EKI beta-gamma

was AR S12407

area: 0870

location: S13W20

S12410 2026.10.09       S08W43            
S12412 2026.10.10       N19W58            
14553 2026.10.10
2026.10.11
  8 2 N06W09 0015   BXO was AR S12413

location: N08W06

14555 2026.10.11 2 1 1 S08W70 0020 CRO AXX was AR S12414

area: 0010

location: S07W68

14554 2026.10.11
2026.10.12
      N07E05           was AR S12415

location: N08E06

14556 2026.10.12
2026.10.13
  3   N03E17 0005   AXX was AR S12416

location: N03E18

S12417 2026.10.12       S23W48            
14557 2026.10.13 15 42 21 N07E16 0080 DSI DAI beta-gamma

split off from AR S12416

area: 0220

14558 2026.10.13
2026.10.14
      S08W62           was AR S12418
S12419 2026.10.15       S07E11          
S12420 2026.10.16   9 7 S19W11 0020   BXO    
S12421 2026.10.16   1 1 N19E05 0008   AXX    
Total spot count: 51 117 65  
Sunspot number: 81 187 125  (total spot count + 10 * number of spotted regions)
Weighted SN: 69 132 80  (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): 81 94 94 (Effective 2026.09.19: SWPC adjustment changed from 1.1 to 1.0, STAR 2K adjustment changed from 0.55 to 0.5, STAR 1K adjustment changed from 0.8 to 0.75)

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO)
Smoothed sunspot number (4) Average ap
(3)
Measured 1 AU
2024.05 187.7 191.9 172.1 149.1 (+4.6) 23.56
(SC25 peak)
2024.08  246.1
(SC25 peak)
252.2 216.0  (SC25 peak) 156.8 (+1.8) 15.96
2024.10 221.0 219.6 165.8 160.9 (+1.5) (SC25 solar max) 18.99
2025.07 137.8 142.3 125.9 122.5 (-2.2) 11.80
2025.08 154.9 158.7 133.7 118.4 (-4.1) 9.97
2025.09 154.4 156.0 129.7 113.1 (-5.3) 14.02
2025.10 139.5 138.6 114.6 108.5 (-4.6) 15.64
2025.11 140.3 137.3 91.7 106.9 (-1.6) 21.01
2025.12 160.8 155.8 124.0 107.0 (-0.1) 13.35
2026.01 148.7 144.0 115.0 104.2 (-2.8) 22.47
2026.02 136.4 133.1 77.4 99.8 (-4.4) 12.88
2026.03 131.0 129.7 86.6 94.5 (-5.3) 15.44
2026.04  120.0 120.9 79.3 (89.6 projected, -4.9) 12.10
2026.05 125.4 128.2 101.4 (87.2 projected, -2.4) 9.80
2026.06 137.9 142.2 94.3 (84.1 projected, -3.1) 9.57
2026.07 134.7 139.0 78.1 (79.2 projected, -4.9) 10.16
2026.08 116.1 119.0 76.0 (77.0 projected, -2.2) 8.67
2026.09 105.0 106.1 60.3 (76.1 projected, -0.9) 7.54
2026.10 113.2 (1)   40.5 (2A) / 78.4 (2B) / 71.5 (2C) (74.0 projected, -2.1) (13.4)
2026.11       (71.2 projected, -2.8)  
2026.12       (68.0 projected, -3.2)  
2027.01       (65.6 projected, -2.4)  
2027.02       (63.8 projected, -1.8)  
2027.03       (62.5 projected, -1.3)  

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 27 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 March 2026

Solar activity appears to have exited the solar max phase as of February 2026 with a strong decrease in the number of sunspots observed. The northern polar field has weakened considerably over the last months, and although there is a chance the the field could recover over the next 1-2 years, there is an increasing chance that solar cycle 26 will be very weak. The southern polar field is not impressive either, however, a southern polar coronal hole has formed early in 2026 and appears to be growing.

All 365 day smoothed sunspot numbers reached a maximum on October 11-12, 2024
. This became the peak of SC25 (365 day smoothed peaks: STAR 1K: 236.1, STAR 2K: 364.3, NOAA SN: 156.0, ISN: 163.9), while the 365d smoothed solar flux peaked on October 13, 2024, just 1.7% below the SC23 peak, and 62.6% above the SC24 peak.

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This report has been prepared by Jan Alvestad. It is based on the analysis of data from whichever 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.