The geomagnetic field was at quiet to major storm levels on December 10. Solar wind speed at SOHO ranged between 328 and 509 km/sec, averaging 383 km/sec (+31 km/sec compared to the previous day). What was likely the late arrival of the shock from the December 6 CME was observed arriving at ACE at 03:24 UT. The main CME body arrived just after 20h UT and caused major geomagnetic storming. The high latitude magnetometer at Andenes was at quiet to severe 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 168.5 - increasing 12.6 over the previous solar rotation.
The 365 day average solar flux at 1 AU was 157.71 (183 days ago). The 81 day average solar flux at 1 AU was 149.1 (41 days ago, this is 50.6% 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 22 (STAR Ap - based on the average of three hour interval ap indices: 22.0). Three hour interval K indices: 23422236 (planetary), 21332336 (Boulder), 33323357 (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 11 active regions using 2K resolution (SN: 250) and in 11 active regions using 1K resolution (SN: 179) SDO/HMI images.
AR 14294 [S16W67] decayed significantly losing spots
and area throughout the region as well as magnetic delta configurations. Flaring frequency decreased after 16h UT. The distance between the leader
spots of AR 14296 and the trailing spots of AR 14294 decreased further and
the two regions are close to merging. C1 flares: C1.8 @ 14:31, C1.9 @ 18:00,
C1.9 @ 22:49 UT
AR 14296 [S14W57] decayed slowly and was mostly quiet.
AR 14299 [N22W47] lost all negative polarity spots and could become
spotless before rotating out of view. C1 flares: C1.8 @ 17:11 UT
AR 14300 [N10W40] was quiet and stable.
AR 14303 [S26E10] decayed slowly and quietly.
AR 14304 [N26W37] developed early in the day. Slow decay was observed
after noon. C1 flares: C1.7 @ 06:53, C1.7 @ 09:43 UT
AR 14305 [S24E18] decayed slowly and was mostly quiet.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
AR S11673 [S10E18] developed slowly and
quietly.
AR S11674 [S15W14] developed slowly and quietly.
AR S11675 [S03E37] was quiet and stable.
New AR S11678 [S17W47] emerged close to the trailing spots of AR
14296 with tiny spots.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C3.5 | 00:14 | 14294 | GOES18 | ||
| C3.2 | 00:21 | 14294 | GOES18 | ||
| C3.5 | 00:37 | 14294 | GOES18 | ||
| C4.5 | 00:46 | 14294 | GOES18 | ||
| C4.2 | 00:58 | 14294 | GOES18 | ||
| C5.5 | 01:10 | 14294 | GOES18 | ||
| C7.8 | 01:25 | S15W58 | 14294 | GOES18 | |
| C4.3 | 01:47 | 14294 | GOES18 | ||
| C3.3 | 02:22 | 14305 | GOES18 | ||
| C3.9 | 02:37 | 14294 | GOES18 | ||
| C8.0 | 02:47 | S15W58 | 14294 | GOES18 | |
| C5.6 | 03:00 | 14304 | GOES18 | ||
| C6.4 | 03:13 | 14294 | GOES18 | ||
| C9.5 | 03:24 | 14296 | GOES18 | ||
| C4.7 | 04:00 | 14304 | GOES18 | ||
| M1.2 | 04:22 | S14W60 | 14294 | GOES18 | |
| C3.9 | 04:52 | 14305 | GOES18 | ||
| C4.1 | 05:03 | S16W47 | 14296 | GOES18 | |
| C3.1 | 05:38 | 14294 | GOES18 | ||
| C3.6 | 06:26 | 14294 | GOES18 | ||
| C2.0 | 07:04 | 14294 | GOES18 | ||
| C2.5 | 07:29 | N23W26 | 14304 | GOES18 | |
| M1.9/1N | 07:37 | S15W62 | 14294 | GOES18 | |
| C2.6 | 08:09 | 14304 | GOES18 | ||
| C2.6 | 08:19 | 14304 | GOES18 | ||
| C2.5 | 08:30 | 14305 | GOES18 | ||
| M1.0/1F | 09:55 | S21W59 | 14294 | GOES18 | |
| C4.1 | 10:33 | S17W68 | 14294 | GOES18 | |
| C2.7 | 10:46 | 14294 | GOES18 | ||
| C2.2 | 11:37 | 14296 | GOES18 | ||
| C2.4 | 12:22 | 14305 | GOES18 | ||
| C2.2 | 13:18 | 14299 | GOES18 | simultaneous flare in AR 14304 | |
| M1.6 | 13:43 | S22W62 | 14294 | GOES18 | moderate type II radio sweep |
| C3.7 | 14:00 | 14294 | GOES18 | ||
| C3.4 | 15:05 | 14294 | GOES18 | ||
| C2.3 | 15:25 | 14304 | GOES18 | ||
| C3.8 | 19:28 | S12W55 | 14296 | GOES18 | simultaneous flare in AR 14294 |
| C2.7 | 20:04 | 14294 | GOES18 | ||
| C2.7 | 20:24 | S10W73 | 14294 | GOES18 | |
| M4.4/2B | 22:08 | S20W66 | 14294 | GOES18 | strong type II radio sweep |
| C2.2 | 22:30 | 14294 | GOES18 | ||
| C4.8 | 23:05 | S09W74 | 14294 | GOES18 |
December 9-10: No obviously Earth directed CMEs were observed in
available coronagraph imagery.
December 8: A partial halo CME became visible in LASCO C2 imagery at
23:00 with most of the ejecta observed off the northwest limb. The most
likely source is the M1.2 flare in AR 14299 peaking at 22:28 UT. There is a
chance that CME components could reach Earth on December 11.
[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 (CH1334) will become Earth facing on December 10-15. A recurrent trans equatorial negative polarity coronal hole (CH1335) could rotate across the central meridian on December 15.
The geomagnetic field is expected to be at quiet to major storm levels on December 11 due to CME effects. Quiet levels are likely on December 12, however, there is a chance that a CME could reach Earth and cause unsettled to active conditions. Effects from CH1334 could cause quiet to minor storm levels on December 13-15.
| 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 | ||||||||||
| 14294 | 2025.11.28 2025.11.28 |
25 | 31 | 17 | S15W69 | 0800 | EKC | EKC |
 |
 |
beta-gamma was AR S11642 location: S16W67 area: 0650 |
| 14296 | 2025.11.29 2025.11.30 |
5 | 16 | 6 | S15W55 | 0420 | EHO | EKO |
 |
 |
was AR S11647 area: 0380 location: S14W57 |
| 14295 | 2025.11.29 2025.11.30 |
N06W70 |
 |
was AR S11648 location: N03W60 |
|||||||
| 14299 | 2025.11.30 2025.12.01 |
6 | 12 | 7 | N21W50 | 0020 | CRO | HRX |
 |
 |
was AR S11649 location: N22W47 |
| 14298 | 2025.12.01 | 2 | S16W89 | 0060 | CSO |
 |
rotated out of view |
||||
| 14300 | 2025.12.01 2025.12.02 |
3 | 1 | N08W45 | 0006 | AXX |
 |
 |
was AR S11654 location: N10W40 |
||
| S11661 | 2025.12.04 | N19W58 |
 |
||||||||
| S11662 | 2025.12.05 | N05W23 | |||||||||
| S11663 | 2025.12.05 | S18W34 | |||||||||
| 14304 | 2025.12.06 2025.12.08 |
15 | 28 | 11 | N26W36 | 0070 | CAI | DAI |
 |
 |
beta-gamma was AR S11664 area: 0230 location: N26W37 |
| 14303 | 2025.12.06 2025.12.07 |
1 | 4 | 3 | S27E10 | 0010 | AXX | HRX |
 |
 |
was AR S11665 area: 0015 location: S26E10 |
| S11668 | 2025.12.07 | S24W10 |
 |
||||||||
| S11669 | 2025.12.07 | S05W43 | |||||||||
| S11670 | 2025.12.07 | N01W13 | |||||||||
| 14305 | 2025.12.08 2025.12.09 |
10 | 25 | 11 | S25E20 | 0070 | DAI | DAO |
 |
 |
was AR S11671 area: 0180 location: S24E18 |
| S11672 | 2025.12.09 | S08W27 |
 |
||||||||
| S11673 | 2025.12.09 | 8 | 4 | S10E22 | 0030 | CRO |
 |
 |
|||
| S11674 | 2025.12.09 | 10 | 7 | S15W14 | 0050 | DRI |
 |
 |
|||
| S11675 | 2025.12.09 | 1 | 1 | S03E37 | 0005 | AXX |
 |
 |
|||
| S11676 | 2025.12.09 | S11E60 |
 |
||||||||
| S11678 | 2025.12.10 | 2 | 1 | S17W47 | 0006 | BXO |
 |
||||
| Total spot count: | 64 | 140 | 69 | ||||||||
| Sunspot number: | 134 | 250 | 179 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 102 | 182 | 111 | (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): | 147 | 138 | 143 | ||||||||
| 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 | 196.6 (1) | 50.1 (2A) / 155.3 (2B) / 135.7 (2C) | (106.3 projected, -1.6) | (14.3) | |
| 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.
