The geomagnetic field was at quiet to unsettled levels on December 31. After 04h UT the phi angle was in a negative sector as weak effects associated with CH1337 became noticeable. Solar wind speed at SOHO ranged between 385 and 496 km/sec, averaging 437 km/sec (+42 km/sec compared to the previous day). The above 10 MeV proton flux was at background levels all day.
Solar flux density measured at 20h UT on 2.8 GHz was 170.5 - decreasing 49.4 over the previous solar rotation.
The 365 day average solar flux at 1 AU was 154.21 (183 days ago). The 81 day average solar flux at 1 AU was 144.1 (41 days ago, this is 47.5% 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: 7.0). Three hour interval K indices: 21223111 (planetary), 11333221 (Boulder), 41113123 (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 10 active regions using 2K resolution (SN: 260) and in 9 active regions using 1K resolution (SN: 162) SDO/HMI images.
AR 14317 [N11W77] gained a magnetic delta
configuration in the southern part of the largest penumbra before noon,
however, this disappeared by the end of the day. C1 flares: C1.4 @ 07:09,
C1.6 @ 09:33, C1.6 @ 21:15 UT
AR 14323 [S14E01] was mostly quiet and stable.C1 flares: C1.6 @ 23:14
UT
AR 14324 [N24E12] produced a major M7.1 flare at 13:51 UT and several
C flares. C1 flares: C1.5 @ 05:52, C1.7 @ 11:34, C1.9 @ 12:44 UT
AR 14325 [S08E05] lost the magnetic delta configuration in the main
penumbra while another delta formed nearby. C1 flares: C1.8 @ 00:27, C1.8 @
00:35, C1.5 @ 03:22, C1.7 @ 07:42, C1.9 @ 12:42, C1.8 @ 19:52 UT
AR 14329 [S11E29] was quiet and stable.
AR 14330 [S17E30] reemerged with tiny spots.
AR 14331 [S25E37] was quiet and stable.
New AR 14332 [N14E30] emerged with tiny spots on December 30 and was
numbered by SWPC the next day.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
New AR S11734 [N07E15] was observed with tiny
spots in an old plage area.
New AR S11735 [S21E46] was observed with a tiny spot in an old plage
area.
An active region behind the southwest limb produced C1 flares: C1.7 @ 03:50, C1.7 @ 04:08, C1.8 @ 04:51 UT.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C5.9 | 01:32 | 14325 | GOES18 | ||
| C2.3 | 05:14 | 14324 | GOES18 | ||
| C2.1 | 06:35 | 14324 | GOES18 | ||
| C3.6 | 09:52 | 14324 | GOES18 | ||
| C3.8 | 10:12 | 14324 | GOES18 | ||
| C2.1 | 11:00 | 14317 | GOES18 | ||
| M7.1 | 13:51 | 14324 | GOES18 | CME weak type II and moderaste type IV radio sweeps |
|
| C3.1 | 17:01 | 14325 | GOES18 | ||
| C2.9 | 17:20 | 14317 | GOES18 | ||
| C2.9 | 17:35 | 14324 | GOES18 | ||
| C2.3 | 17:49 | 14317 | GOES18 | ||
| C2.8 | 18:28 | 14317 | GOES18 | ||
| C2.2 | 22:14 | 14325 | GOES18 |
December 29: A filament eruption near AR 14324 between 18-20h UT was
associated with a partial halo CME.
December 30: No obviously Earth directed CMEs were observed in
available coronagraph imagery.
December 31: A halo CME was observed after the M7 flare in AR 14324.
The CME could reach Earth on January 2.
[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 northern hemisphere negative polarity coronal hole (CH1337) rotated across the central meridian on December 28-30.
The geomagnetic field is expected to be at quiet to minor storm levels on January 1-2 due to effects associated with CH1337, possibly with contributions from the December 29 CME on January 1. Unsettled to major storm levels are possible on January 2-3 due to effects from the DEcember 31 CME.
| 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 | ||||||||||
| 14317 | 2025.12.20 2025.12.20 |
5 | 5 | 4 | N11W76 | 0160 | CAO | HAX |
 |
 |
was AR S11705 area: 0250 location: N11W77 |
| 14318 | 2025.12.21 2025.12.22 |
N05W73 |
 |
was S11707 location: N07W63 |
|||||||
| 14319 | 2025.12.21 2025.12.22 |
S12W54 |
 |
was AR S11708 location: S08W47 |
|||||||
| 14320 | 2025.12.22 2025.12.23 |
N06W45 |
 |
was AR S11710 location: N04W42 |
|||||||
| S11712 | 2025.12.23 | S14W54 | |||||||||
| S11713 | 2025.12.23 | S20W38 | |||||||||
| 14323 | 2025.12.25 2025.12.26 |
8 | 58 | 19 | S17E14 | 0010 | AXX | FRI |
 |
 |
beta-gamma was AR S11719 area: 0110 location: S14E01 |
| 14325 | 2025.12.26 2025.12.27 |
15 | 35 | 22 | S08E04 | 0280 | EKI | EKC |
 |
 |
beta-gamma-delta was AR S11720 area: 0670 location: S08E06 |
| 14324 | 2025.12.26 2025.12.26 |
15 | 37 | 19 | N24E11 | 0200 | DAI | DSI |
 |
 |
beta-delta was AR S11721 area: 0280 location: N24E12 |
| S11722 | 2025.12.26 | N15W12 | |||||||||
| 14326 | 2025.12.27 2025.12.28 |
S03W77 |
was AR S11723 location: S03W72 |
||||||||
| 14330 | 2025.12.27 2025.12.29 |
5 | S16E28 | 0007 | BXO |
 |
was AR S11724 location: S17E30 |
||||
| S11725 | 2025.12.27 | N23W36 | |||||||||
| S11726 | 2025.12.27 | N19W58 | |||||||||
| 14327 | 2025.12.28 2025.12.28 |
S21W63 | was AR S11728 | ||||||||
| 14331 | 2025.12.28 2025.12.29 |
1 | 2 | 2 | S25E37 | 0020 | HRX | HRX |
 |
 |
was AR S11729 |
| 14328 | 2025.12.29 | 10 | S13W07 | 0020 | CRO | leader spots of AR 14323 | |||||
| 14329| | 2025.12.29 2025.12.29 |
4 | 1 | S12E22 | 0007 | BXO |
 |
 |
was AR S11731 location: S12E29 |
||
| 14332 | 2025.12.30 2025.12.31 |
3 | 6 | 2 | N14E31 | 0010 | BXO |
 |
 |
was AR S11732 area: 0015 location: N14E30 |
|
| S11733 | 2025.12.30 | N11W29 |
 |
||||||||
| S11734 | 2025.12.31 | 7 | 2 | N07E15 | 0015 | BXO |
 |
||||
| S11735 | 2025.12.31 | 1 | 1 | S21E46 | 0003 | AXX |
 |
||||
| Total spot count: | 57 | 160 | 72 | ||||||||
| Sunspot number: | 127 | 260 | 162 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 83 | 186 | 98 | (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): | 140 | 143 | 130 | ||||||||
| 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 |
| 2024.11 | 199.6 | 195.3 | 154.1 | 157.2 (-3.7) | 9.33 |
| 2024.12 | 197.3 | 191.2 | 154.6 | 151.2 (-6.0) | 8.42 |
| 2025.01 | 190.3 | 184.2 | 137.0 | 146.2 (-5.0) | 13.17 |
| 2025.02 | 184.2 | 179.7 | 155.7 | 139.8 (-6.4) | 14.42 |
| 2025.03 | 163.7 | 162.1 | 134.2 | 135.9 (-3.9) | 15.96 |
| 2025.04 | 162.5 | 163.6 | 141.4 | 133.3 (-2.6) | 17.62 |
| 2025.05 | 135.3 | 138.3 | 78.5 | 128.5 (-4.8) | 17.26 |
| 2025.06 | 131.3 | 135.4 | 114.6 | 124.7 (-3.8) | 21.43 |
| 2025.07 | 137.8 | 142.3 | 125.6 | (122.4 projected, -2.3) | 11.80 |
| 2025.08 | 154.9 | 158.7 | 133.5 | (119.3 projected, -3.1) | 9.97 |
| 2025.09 | 154.4 | 156.0 | 129.8 | (115.8 projected, -3.5) | 14.02 |
| 2025.10 | 139.5 | 138.6 | 114.6 | (111.8 projected, -4.0) | 15.64 |
| 2025.11 | 140.3 | 137.3 | 91.7 | (109.5 projected, -2.3) | 21.01 |
| 2025.12 | 160.8 | 155.8 | 124.0 | (108.0 projected, -1.5) | 13.8 |
| 2026.01 | (1) | (2A/2B) / 138.2 (2C) | (104.0 projected, -4.0) | () | |
| 2026.02 | (99.9 projected, -4.1) | ||||
| 2026.03 | (95.5 projected, -4.4) | ||||
| 2026.04 | (91.8 projected, -3.7) | ||||
| 2026.05 | (90.5 projected, -1.3) | ||||
| 2026.06 | (88.4 projected, -2.1) | ||||
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 was on a decreasing trend from September
2024 until mid August 2025 (using the average solar flux over 3 solar rotations as a proxy).
Then a strong surge in activity saw solar flux peak in late August 2025 just
below the largest peaks seen in 2024. A slow decrease in activity from the
August level has been observed in September and October 2025.
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.
--------------------------------------------------------------------------------------
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.
