Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 18, 2023 at 07:25 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 8, 2023)
Solar cycle Solar cycles 23-25 (October 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (October 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 (October 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (October 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 very quiet on October 17. Solar wind speed at SOHO ranged between 301 and 350 km/sec. The high latitude magnetometer at Andenes recorded quiet to unsettled levels. A weak disturbance associated with CH1079 began early on October 18.

Solar flux density measured at 20h UT on 2.8 GHz was 137.3 - decreasing 18.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 155.44. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.8). Three hour interval K indices: 20101000 (planetary), 20101100 (Boulder), 00000003 (Andenes).

The background x-ray flux is at the class B5 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 11 active regions using 2K resolution (SN: 181) and in 9 active regions using 1K resolution (SN: 120) SDO/HMI images.

Region 13464 [N04W33] was mostly quiet and stable.
Region 13465 [N11W10] decayed slowly and was mostly quiet. C1 flares: C1.6 @ 02:10, C1.8 @ 05:58 UT
Region 13467 [N13E27] was mostly quiet and stable.
Region 13468 [S10E57] was quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9053 [N21W35] was quiet and stable.
S9063 [N04E45] was quiet and stable.
S9064 [S11W04] was quiet and stable.
S9067 [N25E69] was quiet and stable
New region S9069 [S08W56] emerged with tiny spots before noon, them decayed slowly.
New region S9070 [N24W75] emerged with tiny spots.
New region S9071 [N02E06] emerged with tiny spots.

AR 13463 produced a C1.1 flare at 04:36 UT.
A C1.0 flare was recorded at 07:33 from a source behind the northwest limb. The same source produced another C1.0 flare at 14:02 UT
AR S9109 behind the southwest limb was the origin of a C1.0 flare at 21:14 UT

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.2 05:04   13463 GOES18 partial halo CME

Coronal mass ejections (CMEs)

October 15: No obviously Earth directed CMEs were observed.
October 16: A partial halo CME was observed after C flares in AR 13467 around 11 UT. This CME could reach Earth on October 19.
October 17: A partial halo CME was observed after a C flare in AR 13463 early in the day. This CME could reach Earth on October 20.

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 southern hemisphere negative polarity coronal hole (CH1180) was Earth facing on October 16.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is very good. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet with a chance of unsettled intervals on October 18-20 due to effects from CH1179 and CH1180. If the October 16 and 17 CMEs reach Earth, we could see unsettled to minor storm conditions on October 19-20.

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
13461 2023.10.05
2023.10.08
      N13W86           location: N11W71
13462 2023.10.06
2023.10.08
      N20W55           location: N19W52
13463 2023.10.08
2023.10.09
      S17W44         location: S18W44
13466 2023.10.08
2023.10.11
      N08W76        

location: N07W78

13464 2023.10.09
2023.10.10
7 14 8 N04W33 0090 CSO CSO

area: 0120

13465 2023.10.10
2023.10.11
19 19 12 N10W10 0220 CAO CAO location: N11W10
S9052 2023.10.12       S25W36            
S9053 2023.10.12   6   N21W35 0010   AXX  
S9054 2023.10.12       S00E03            
S9056 2023.10.12       N18W57            
13467 2023.10.13
2023.10.14
  9 2 N13E28 0020   BXO

location: N13E27

S9059 2023.10.14       S20W55            
13468 2023.10.15
2023.10.16
1 3 1 S11E56 0130 HAX CSO  
S9063 2023.10.15   2 1 N04E45 0004   BXO  
S9064 2023.10.15   7 2 S11W04 0015   BXO  
S9065 2023.10.15       N07E16            
S9066 2023.10.15       N20W08            
S9067 2023.10.16   4 2 N25E69 0015   ERO  
S9069 2023.10.17   3   S08W56 0005   BXO    
S9070 2023.10.17   2 1 N24W75 0004   AXX    
S9071 2023.10.17   2 1 N02E06 0005   BXO    
Total spot count: 27 71 30  
Sunspot number: 57 181 120  (total spot count + 10 * number of spotted regions)
Weighted SN: 42 89 48  (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): 63 100 96  

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
2022.03 117.0 115.8 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 92.6 (+5.9) 10.92
2022.09 135.1 136.5 96.0 96.5 (+3.9) 12.18
2022.10 133.5 132.7 95.5 98.9 (+2.4) 11.16
2022.11 123.4 120.7 80.5 101.1 (+2.2) 9.33
2022.12 147.9 143.4 112.8 106.7 (+5.6) 10.99
2023.01 182.4 176.6 144.4 113.4 (+6.7) 8.73
2023.02 167.2 163.2 111.3 117.9 (+3.5) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 123.3 121.2 (+3.3) 14.42
2023.04 145.4 146.4 97.6 (126.6 projected, +5.4) 13.40
2023.05 155.6 159.2 137.4 (132.2 projected, +5.6) 10.67
2023.06 161.7 166.8 160.5 (135.4 projected, +3.2) 8.95
2023.07  176.4 182.2 159.1 (135.8 projected, +0.4) 8.15
2023.08  153.7 157.6 114.9 (137.6 projected, +1.8) 7.19
2023.09  154.4 156.0 133.6 (141.0 projected, +3.4) 14.26
2023.10  154.2 (1)   69.8 (2A) / 127.3 (2B) / 149.1 (2C) (142.8 projected, +1.8) (6.1)
2023.11       (145.4 projected max SC25, +2.6)  
2023.12       (144.5 projected, -0.9)  
2024.01       (141.7 projected, -2.8)  
2024.02       (141.5 projected, -0.2)  
2024.03       (141.0 projected, -0.5)  
2024.04       (138.2 projected, -2.8)  

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 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 forecast 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, however, there is a small probability 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.