The geomagnetic field was at quiet to unsettled levels on October 20, weakly under the influence of effects associated with CH1323. Solar wind speed at SOHO ranged between 498 and 636 km/sec, averaging 554 km/sec (+6 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to active 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
140.4 -
decreasing 30.9
over the previous solar rotation.
The 365 day average solar flux at 1 AU was 164.95 (183 days ago). The 81 day
average solar flux at 1 AU was 154.8 (41 days ago, this is 54.2% 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 7 (STAR Ap - based on the average of three hour interval ap indices: 7.4). Three hour interval K indices: 33212112 (planetary), 23312322 (Boulder), 33312124 (Andenes).
The background x-ray flux is at the class C1 level (GOES 19).
At the time of counting spots (see image time), spots were observed in 13 active regions using 2K resolution (SN: 230) and in 12 active regions using 1K resolution (SN: 165) SDO/HMI images.
AR 14252 [S13W40] was quiet and stable.
AR 14254 [N10W06] was quiet and stable.
AR 14256 [S16E13] decayed slowly and quietly.
AR 14257 [S09E35] was mostly quiet and stable.
AR 14258 [S15W72] decayed and was spotless at noon. Then new flux
emerged and a few spots formed. C1 flares: C1.8 @ 17:17 UT
AR 14259 [S19E33] was quiet and stable.
AR 14260 [S10E47] was quiet and stable.
New AR 14261 [S06E66] rotated into view on October 19 and was
numbered the next day by SWPC.
New AR 14262 [S13E36] rotated into view on October 17 and received
its NOAA number 3 days later as SWPC finally decided to make a split from AR
14257.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S11533 [N05E00] reemerged with several spots.
S11538 [N14E28] reemerged with tiny spots.
S11544 [N08E67] was quiet and stable.
New AR S11546 [N11E33] emerged with tiny spots.
AR 14250 produced C1 flares while at the northwest limb: C1.6 @ 11:02, C1.3 @ 14:03, C1.3 @ 14:20, C1.9 @ 00:01 (flare started at 23:57) UT
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C5.9 | 02:34 | behind northwest limb | 14246 | GOES18 | |
| C6.4 | 04:11 | northwest limb | 14250 | GOES18 | |
| M1.0 | 05:27 | northwest limb | 14250 | GOES18 | |
| C3.5 | 07:48 | northwest limb | 14250 | GOES18 | |
| C2.6 | 09:55 | northwest limb | 14250 | GOES18 | |
| C3.0 | 15:45 | 14262 | GOES18 | LDE | |
| C2.2 | 23:24 | northwest limb | 14250 | GOES18 |
October 18-20: No obviously Earth directed CMEs observed in available coronagraph imagery.
[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 negative polarity northern hemisphere coronal hole (CH1323) was Earth facing on October 15-18.
The geomagnetic field is expected to be at quiet to unsettled levels on October 21 due to effects associated with CH1323. Quiet levels are likely on October 22-23.
| 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.
(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 | ||||||||||
| 14248 | 2025.10.09 2025.10.10 |
5 | N06W95 | 0380 | DKO |
spotless location: N05W80 SWPC swapped
location for ARs |
|||||
| 14250 | 2025.10.09 2025.10.10 |
N06W94 |
 |
was AR S11511 SWPC deleted AR 14250 from |
|||||||
| 14251 | 2025.10.10 2025.10.12 |
N19W71 |
was AR S11514 location: N19W76 |
||||||||
| 14252 | 2025.10.11 2025.10.12 |
1 | 11 | 5 | S12W42 | 0090 | HSX | DSO |
 |
 |
was AR S11517 area: 0190 location: S13W40 |
| S11520 | 2025.10.12 | N10W51 | |||||||||
| 14254 | 2025.10.13 2025.10.14 |
1 | 8 | 3 | N10W08 | 0080 | HSX | CSO |
 |
 |
was AR S11523 area: 0110 location: N10W06 |
| S11524 | 2025.10.13 | S04W34 |
 |
||||||||
| S11525 | 2025.10.13 | S23W51 | |||||||||
| 14255 | 2025.10.14 2025.10.16 |
S08W16 |
was AR S11526 location: S08W12 |
||||||||
| 14256 | 2025.10.15 2025.10.16 |
4 | 22 | 9 | S15E12 | 0030 | HRX | DRI |
 |
 |
was AR S11529 location: S16E13 |
| S11530 | 2025.10.16 | N22W03 | |||||||||
| S11531 | 2025.10.16 | N15W24 | |||||||||
| 14258 | 2025.10.16 2025.10.18 |
5 | 3 | S14W69 | 0015 | BXO |
 |
 |
was AR S11532 location: S15W72 |
||
| S11533 | 2025.10.17 | 12 | 8 | N05E00 | 0050 | DRI |
 |
||||
| 14257 | 2025.10.17 | 3 | 1 | 1 | S09E35 | 0110 | DSO | HSX |
 |
 |
was AR S11534 area: 0180 |
| S11535 | 2025.10.17 | S20W38 | |||||||||
| 14262 | 2025.10.17 2025.10.20 |
1 | 9 | 5 | S12E35 | 0150 | HSX | CAO |
 |
 |
was AR S11536 area: 0230 location: S13E36 |
| S11537 | 2025.10.17 | N06W10 | |||||||||
| S11538 | 2025.10.17 | 5 | 2 | N14E28 | 0010 | BXO |
 |
||||
| 14259 | 2025.10.18 2025.10.19 |
1 | 14 | 5 | S20E35 | 0010 | BXO | BXO |
 |
 |
was AR S11539 area: 0030 location: S19E33 |
| 14260 | 2025.10.18 2025.10.19 |
1 | 3 | 1 | S09E47 | 0010 | AXX | CRO |
 |
 |
was AR S11540 location: S10E47 |
| S11541 | 2025.10.18 | N48W15 | |||||||||
| 14261 | 2025.10.19 2025.10.20 |
2 | 5 | 2 | S05E67 | 0040 | DAO | CSO |
 |
 |
was AR S11543 area: 0100 location: S06E66 |
| S11544 | 2025.10.19 | 2 | 1 | N08E67 | 0020 | HRX |
 |
 |
|||
| S11545 | 2025.10.19 | S22W17 |
 |
||||||||
| S11546 | 2025.10.20 | 3 | N11E33 | 0006 | BXO |
 |
|||||
| Total spot count: | 19 | 100 | 45 | ||||||||
| Sunspot number: | 109 | 230 | 165 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 57 | 138 | 83 | (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): | 120 | 127 | 132 | ||||||||
| Month | Average solar flux | International sunspot number (WDC-SILSO) |
Smoothed sunspot number (4) | Average
ap (3) |
|
|---|---|---|---|---|---|
| Measured | 1 AU | ||||
| 2024.04 | 161.3 | 162.6 | 137.0 | 144.5 (+3.1) | 9.69 |
| 2024.05 | 187.7 | 191.9 | 172.1 | 149.1 (+4.6) | 23.56 (SC25 peak) |
| 2024.06 | 184.3 | 190.2 | 164.1 | 152.8 (+3.7) | 10.24 |
| 2024.07 | 196.6 | 203.0 | 196.8 | 155.0 (+2.3) | 7.13 |
| 2024.08 | 246.1 (cycle peak) |
252.2 | 216.0 (SC25 peak) | 156.8 (+1.8) | 15.96 |
| 2024.09 | 195.7 | 197.8 | 141.1 | 159.4 (+1.6) | 15.36 |
| 2024.10 | 221.0 | 219.6 | 165.8 | 160.9 (+1.5) (SC25 solar max) | 18.99 |
| 2024.11 | 199.6 | 195.3 | 154.1 | 157.1 (-3.8) | 9.33 |
| 2024.12 | 197.3 | 191.2 | 154.6 | 151.3 (-5.8) | 8.42 |
| 2025.01 | 190.3 | 184.2 | 137.0 | 146.3 (-5.0) | 13.17 |
| 2025.02 | 184.2 | 179.7 | 155.7 | 139.9 (-6.4) | 14.42 |
| 2025.03 | 163.7 | 162.1 | 134.2 | 136.0 (-3.9) | 15.96 |
| 2025.04 | 162.5 | 163.6 | 140.6 | (133.7 projected, -2.3) | 17.62 |
| 2025.05 | 135.3 | 138.3 | 79.2 | (130.1 projected, -3.6) | 17.26 |
| 2025.06 | 131.3 | 135.4 | 116.3 | (126.3 projected, -3.8) | 21.43 |
| 2025.07 | 137.8 | 142.3 | 125.6 | (123.0 projected, -3.3) | 11.80 |
| 2025.08 | 154.9 | 158.7 | 133.6 | (119.4 projected, -3.6) | 9.97 |
| 2025.09 | 154.4 | 156.0 | 129.6 | (115.5 projected, -3.9) | 14.1 |
| 2025.10 | 147.3 (1) | 75.9 (2A) / 117.7 (2B) / 162.2 (2C) ISN month to dato average: 125 At this level the April 2025 SSN would become 133.9 |
(111.5 projected, -4.0) | (18.0) | |
| 2025.11 | (109.3 projected, -2.2) | ||||
| 2025.12 | (107.6 projected, -1.7) | ||||
| 2026.01 | (103.5 projected, -4.1) | ||||
| 2026.02 | (99.4 projected, -4.1) | ||||
| 2026.03 | (95.0 projected, -4.4) | ||||
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 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
Sunspot activity has been on a decreasing trend since September
2024 (using the average solar flux over 3 solar rotations as a proxy).
Compared to the peak of SC25 solar flux has been at a low level in both May
and June 2025. Taking a closer look at the 81 day (3 solar rotations)
average solar flux proxy, its peak was in early September 2024 and had on
May 12 decreased to less than half of the solar cycle flux range.
Subtracting the 81 day average of approximately 69 at solar cycle minimum
from all measurements, the SC25 range is 0 - 158.3.
All 365 day smoothed sunspot numbers peaked on October 11-12, 2024,
very likely making this the peak of SC25 (365 day smoothed peaks: STAR 1K: 236.1, STAR 2K: 364.3, NOAA SN: 156.0, ISN: 163.9). The 365d
smoothed solar flux peaked on October 13, 2024, just 1.7% below the SC23
peak, and 62.6% above the SC24 peak.
--------------------------------------------------------------------------------------
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.
