The geomagnetic field was at quiet to unsettled levels on December 30. Solar wind speed at SOHO ranged between 367 and 457 km/sec, averaging 395 km/sec (-14 km/sec compared to the previous day). The high latitude magnetometer at Andenes was at 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 182.1 - decreasing 27.4 over the previous solar rotation.
The 365 day average solar flux at 1 AU was 154.33 (183 days ago). The 81 day average solar flux at 1 AU was 143.7 (41 days ago, this is 47.2% 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: 6.9). Three hour interval K indices: 11213321 (planetary), 12213322 (Boulder), 11203433 (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 12 active regions using 2K resolution (SN: 299) and in 10 active regions using 1K resolution (SN: 187) SDO/HMI images.
AR 14317 [N11W63] was mostly quiet and stable.
AR 14318 [N07W50] decayed slowly and quietly.
AR 14319 [S08W34] was quiet and stable.
AR 14320 [N04W29] was quiet and stable.
AR 14321 [S11W87] rotated partly out of view
and produced several low level C flares as the region decayed further. C1
flares: C1.9 @ 01:32, C1.9 @ 01:58, C1.9 @ 12:32, C1.9 @ 20:55, C1.9 @ 22:09
UT
AR 14323 [S14E12] gained spots in the leading polarity section. C1
flares: C1.8 @ 23:06 UT
AR 14324 [N24E25] gained tiny spots, however, some area was lost and
the magnetic delta configuration disappeared. The region displayed much less
flare activity than during previous days.
AR 14325 [S08E18] matured and still has a magnetic delta
configuration in the leading part of the trailing spot section. C1 flares:
C1.8 @ 05:09, C1.8 @ 12:29, C1.8 @ 22:38 UT
AR 14329 [S12E36] decayed slowly and quietly.
AR 14331 [S25E50] decayed slowly and quietly.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
New AR S11732 [N14E44] emerged with tiny spots.
New AR S11733 [N11W16] emerged with a tiny spot.
Minor update posted at 17:35 UT: AR 14324 was the origin of an M7.1 flare at 13:51 UT. Moderate type IV and a weak type II radio sweep were recorded, and a halo CME was associated with the flare. The CME could reach Earth on January 2.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C4.9 | 00:27 | S09E38 | 14325 | GOES18 | |
| C2.3 | 00:53 | 14317 | GOES18 | ||
| C3.0 | 01:03 | S09E39 | 14325 | GOES18 | |
| C2.5 | 01:14 | 14325 | GOES18 | ||
| C2.3 | 02:26 | 14325 | GOES18 | ||
| C2.0 | 02:46 | 14324 | GOES18 | ||
| C2.0 | 03:24 | 14325 | GOES18 | ||
| C2.2 | 03:58 | 14325 | GOES18 | ||
| C2.3 | 04:05 | 14323 | GOES18 | ||
| C2.0 | 04:25 | 14321 | GOES18 | ||
| C2.2 | 05:53 | 14325 | GOES18 | ||
| C3.5 | 06:31 | 14324 | GOES18 | ||
| C5.0 | 06:45 | 14325 | GOES18 | simultaneous flare in AR 14323 | |
| C3.8 | 06:49 | 14324 | GOES18 | ||
| C3.4 | 07:31 | 14321 | GOES18 | ||
| C3.4 | 07:47 | 14324 | GOES18 | ||
| C3.5 | 08:24 | 14325 | GOES18 | ||
| C4.6 | 08:43 | 14325 | GOES18 | simultaneous flare in AR 14321 | |
| C4.0 | 08:57 | 14321 | GOES18 | ||
| C2.7 | 09:49 | 14325 | GOES18 | ||
| C2.5 | 10:21 | 14321 | GOES18 | ||
| C2.1 | 10:53 | 14325 | GOES18 | ||
| C2.3 | 11:16 | 14325 | GOES18 | ||
| C2.5 | 11:37 | 14325 | GOES18 | ||
| C2.2 | 12:57 | 14325 | GOES18 | ||
| C2.2 | 14:22 | 14325 | GOES18 | ||
| C2.5 | 15:47 | 14325 | GOES18 | ||
| C4.9 | 15:55 | 14325 | GOES18 | simultaneous flare in AR 14321 | |
| C3.2 | 16:16 | 14325 | GOES18 | ||
| C4.1 | 18:03 | S17E43 (SDO/AIA) | 14330 | GOES18 | |
| C2.2 | 22:48 | 14325 | GOES18 | ||
| C2.8 | 23:40 | 14325 | GOES18 |
December 28: A partial halo CME was observed after the M4 event in AR
14318. Components of the CME could reach Earth on December 31.
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.
[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 December 31-January 2 due to effects associated with CH1337, possibly with contributions from the December 28 CME on December 31 and January 1 and the December 29 CME on January 1.
| 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 |
7 | 14 | 7 | N11W62 | 0200 | DSO | CSO |
 |
 |
was AR S11705 area: 0250 location: N11W63 |
| 14318 | 2025.12.21 2025.12.22 |
3 | N05W59 | 0006 | AXX |
 |
 |
was S11707 location: N07W50 |
|||
| 14319 | 2025.12.21 2025.12.22 |
8 | 2 | S12W40 | 0013 | BXO |
 |
 |
was AR S11708 location: S08W34 |
||
| 14321 | 2025.12.22 2025.12.24 |
8 | 1 | 1 | S10W90 | 0320 | DKC | HAX |
 |
 |
was AR S11709 area: 0050 location: S11W87 |
| 14320 | 2025.12.22 2025.12.23 |
2 | N06W30 | 0003 | BXO |
 |
 |
was AR S11710 location: N04W29 |
|||
| S11712 | 2025.12.23 | S14W41 |
 |
||||||||
| S11713 | 2025.12.23 | S20W25 | |||||||||
| 14323 | 2025.12.25 2025.12.26 |
5 | 65 | 22 | S16E26 | 0010 | BXI | FRI |
 |
 |
beta-gamma was AR S11719 area: 0110 location: S14E12 |
| 14325 | 2025.12.26 2025.12.27 |
11 | 38 | 27 | S08E17 | 0220 | EKI | EKC |
 |
 |
beta-gamma-delta was AR S11720 area: 0680 location: S08E18 |
| 14324 | 2025.12.26 2025.12.26 |
10 | 37 | 22 | N24E22 | 0200 | DAO | DAI |
 |
 |
was AR S11721 area: 0300 location: N24E25 |
| S11722 | 2025.12.26 | N15E01 | |||||||||
| 14326 | 2025.12.27 2025.12.28 |
S03W63 |
was AR S11723 location: S03W59 |
||||||||
| 14330 | 2025.12.27 2025.12.29 |
3 | S16E41 | 0010 | BXO |
 |
was AR S11724 location: S16E42 spotless |
||||
| S11725 | 2025.12.27 | N23W23 | |||||||||
| S11726 | 2025.12.27 | N19W45 | |||||||||
| S11727 | 2025.12.28 | N17W57 | |||||||||
| 14327 | 2025.12.28 2025.12.28 |
S21W49 | was AR S11728 | ||||||||
| 14331 | 2025.12.28 2025.12.29 |
1 | 2 | 2 | S25E50 | 0020 | HRX | CAO |
 |
 |
was AR S11729 area: 0030 |
| S11730 | 2025.12.28 | S24W50 |
 |
||||||||
| 14328 | 2025.12.29 | 4 | S14E08 | 0030 | CRO | leader spots of AR 14323 | |||||
| 14329| | 2025.12.29 2025.12.29 |
2 | 3 | 1 | S12E35 | 0010 | BXO | CRO |
 |
 |
was AR S11731 area: 0020 location: S12E48 |
| S11732 | 2025.12.30 | 5 | 2 | N14E44 | 0010 | BXO |
 |
||||
| S11733 | 2025.12.30 | 1 | 1 | N11W16 | 0002 | AXX |
 |
||||
| Total spot count: | 51 | 179 | 87 | ||||||||
| Sunspot number: | 141 | 299 | 187 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 87 | 215 | 123 | (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): | 155 | 164 | 150 | ||||||||
| 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 |
| 2024.09 | 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 | 157.2 (-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 | (124.4 projected, -4.1) | 21.43 |
| 2025.07 | 137.8 | 142.3 | 125.6 | (121.7 projected, -2.7) | 11.80 |
| 2025.08 | 154.9 | 158.7 | 133.5 | (118.0 projected, -3.7) | 9.97 |
| 2025.09 | 154.4 | 156.0 | 129.8 | (114.1 projected, -3.9) | 14.02 |
| 2025.10 | 139.5 | 138.6 | 114.6 | (110.1 projected, -4.0) | 15.64 |
| 2025.11 | 140.3 | 137.3 | 91.7 | (107.9 projected, -2.2) | 21.01 |
| 2025.12 | 160.5 (1) | 114.2 (2A) / 118.0 (2B) / 139.4 (2C) ISN average to date: 118. At this level the SSN for June 2025 will become 124.4 |
(106.3 projected, -1.6) | (14.1) | |
| 2026.01 | (102.3 projected, -4.0) | ||||
| 2026.02 | (98.2 projected, -4.1) | ||||
| 2026.03 | (93.8 projected, -4.4) | ||||
| 2026.04 | (90.1 projected, -3.7) | ||||
| 2026.05 | (88.9 projected, -1.2) | ||||
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 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.
