The geomagnetic field was quiet to major storm on December 18, first under the influence of CME effects and after 18h under the influence of a high speed stream from CH1193. Solar wind speed at SOHO ranged between 490 and 669 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.
Solar flux density measured at 20h UT on 2.8 GHz was 161.4 - decreasing 10.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.89. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.42 on June 4, 2023). The Potsdam WDC planetary A index was 26 (STAR Ap - based on the mean of three hour interval ap indices: 26.3). Three hour interval K indices: 24643335 (planetary), 23554333 (Boulder), 32443355 (Andenes).
The background x-ray flux is at the class C1 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 349) and in 14 active regions using 1K resolution (SN: 227) SDO/HMI images.
Region 13516 [S17W52] decayed slowly and quietly.
Region 13518 [N14W04] was quiet and stable.
Region 13519 [S11W30] gained spots as new flux emerged to the north
of the main penumbrae, this caused weak polarity intermixing.
Region 13521 [N11E32] gained spots, lost area and was quiet
Region 13522 [S04W01] decayed slowly and quietly.
Region 13523 [N23E39] gained spots and was quiet.
Region 13524 [N27E38] gained trailing spots and was mostly quiet.
Region 13525 [S08E18] decayed slowly and quietly.
Region 13526 [N14E58] developed slowly and produced a few flares. C1
flares: C1.9 @ 02:00 UT
New region 13527 [S02W58] emerged on December 17 and was numbered by
SWPC the next day as the region matured.
New region 13528 [N08E14] emerged on December 16 with SWPC numbering
the region 2 days later. The region developed fairly quickly on December 18
and a minor M class flare is possible due to minor polarity intermixing.
New region 13529 [S19E51] rotated into view on December 16 and has
developed slowly since then. SWPC numbered the region on Dec.18.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9238 [N28W18] reemerged with a tiny spot.
S9247 [N14E41] was quiet and stable.
New region S9250 [N09E79] rotated into view with several spots.
New region S9251 [S18W04] was observed with a tiny spot in an old plage area.
AR 13514 behind the northwest limb produced a C1.7 flare at 03:24 UT
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.2 | 00:26 | 13519 | GOES16 | ||
| C2.1 | 01:28 | 13514 | GOES16 | ||
| C6.0 | 02:55 | N26E67 | 13524 | GOES16 | |
| C2.1 | 03:40 | 13519 | GOES16 | ||
| C4.2 | 04:08 | 13526 | GOES16 | ||
| C2.0 | 06:49 | 13526 | GOES16 | ||
| C2.4 | 07:05 | 13514 | GOES16 | ||
| C2.4 | 07:37 | 13514 | GOES16 | ||
| C2.0 | 09:34 | 13519 | GOES16 | simultaneous flare in AR 13514 | |
| C3.1 | 10:29 | 13514 | GOES16 | ||
| C3.6 | 10:39 | 13514 | GOES16 | ||
| C2.6 | 11:08 | 13514 | GOES16 | ||
| C2.3 | 12:09 | 13526 | GOES16 | ||
| C2.3 | 12:36 | 13514 | GOES16 | ||
| C2.5 | 13:08 | 13514 | GOES16 | ||
| C2.4 | 13:56 | 13526 | GOES16 | ||
| C6.5 | 14:22 | 13528 | GOES16 | ||
| C4.4 | 15:21 | 13514 | GOES16 | ||
| C2.7 | 16:54 | 13514 | GOES16 | ||
| C2.1 | 17:54 | 13528 | GOES16 | ||
| C2.3 | 18:04 | 13528 | GOES16 | ||
| C2.3 | 19:09 | 13514 | GOES16 | ||
| C4.5 | 19:25 | 13528 | GOES16 | ||
| C4.0 | 20:36 | 13526 | GOES16 | ||
| C2.9 | 21:03 | 13528 | GOES16 |
December 16-18: No obviously Earth directed CME observed.
[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 positive polarity northern hemisphere coronal hole (CH1193) was Earth facing on December 14-16.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to minor storm on December 19 due to effects from CH1193. Quiet to unsettled is likely on December 20 becoming quiet on December 21. There's a slight chance of unsettled intervals on December 21-22 due to possible effects from CH1193. CH1193 may be too far to the south to cause a disturbance.
| 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 |
Magnetic (SDO) |
SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 13516 | 2023.12.08 2023.12.08 |
5 | S18W54 | 0005 | BXO |
 |
 |
location: S17W52 |
|||
| 13515 | 2023.12.08 2023.12.08 |
S14W57 | |||||||||
| 13518 | 2023.12.12 2023.12.12 |
8 | 3 | N13W07 | 0015 | BXO |
 |
 |
location: N14W04 |
||
| 13519 | 2023.12.12 2023.12.13 |
11 | 37 | 16 | S11W28 | 0130 | DSI | DSI |
 |
 |
beta-gamma location: S11W30 |
| 13521 | 2023.12.14 2023.12.15 |
8 | 20 | 8 | N11E36 | 0050 | DAO | BXO |
 |
 |
area: 0040 location: N11E32 |
| S9238 | 2023.12.14 | 1 | N30W14 | 0001 | AXX |
 |
|||||
| 13523 | 2023.12.15 2023.12.16 |
2 | 8 | 4 | N22E38 | 0010 | BXO | BXO |
 |
 |
area: 0020 location: N23E39 |
| 13525 | 2023.12.15 2023.12.16 |
1 | 5 | 3 | S09E17 | 0010 | AXX | CRO |
 |
 |
|
| 13522 | 2023.12.15 2023.12.16 |
4 | 2 | S03W03 | 0008 | BXO |
 |
 |
location: S04W01 | ||
| 13524 | 2023.12.15 2023.12.16 |
1 | 6 | 3 | N27E36 | 0010 | AXX | CRO |
 |
 |
location: N27E38 area: 0020 |
| 13526 | 2023.12.16 2023.12.17 |
2 | 19 | 8 | N15E57 | 0030 | CAO | CAI |
 |
 |
area: 0110 location: N14E58 |
| 13528 | 2023.12.16 2023.12.18 |
9 | 31 | 16 | N09E12 | 0040 | DSI | DAI |
 |
 |
area: 0200 location: N08E14 |
| 13529 | 2023.12.16 2023.12.18 |
8 | 27 | 14 | S20E56 | 0060 | DSI | DAI |
 |
 |
area: 0180 location: S19E51 |
| 13527 | 2023.12.17 | 5 | 5 | 3 | S03W56 | 0040 | CAO | DSO |
 |
 |
area: 0120 |
| S9247 | 2023.12.17 | 4 | 3 | N14E41 | 0010 | AXX |
 |
 |
|||
| S9248 | 2023.12.17 | S21E32 |
 |
||||||||
| S9249 | 2023.12.17 | N21W32 |
 |
||||||||
| S9250 | 2023.12.18 | 8 | 3 | N09E79 | 0150 | DAO |
 |
||||
| S9251 | 2023.12.18 | 1 | 1 | S18W04 | 0003 | AXX |
 |
||||
| Total spot count: | 47 | 189 | 87 | ||||||||
| Sunspot number: | 137 | 349 | 227 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 77 | 225 | 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): | 151 | 192 | 182 | ||||||||
| 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 |
| 2022.04 | 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 | 101.2 (+2.3) | 9.33 |
| 2022.12 | 147.9 | 143.4 | 112.8 | 106.7 (+5.5) | 10.99 |
| 2023.01 | 182.4 | 176.6 | 144.4 | 113.3 (+6.6) | 8.73 |
| 2023.02 | 167.2 | 163.2 | 111.3 | 117.8 (+3.5) | 14.48 (current SC25 peak) |
| 2023.03 | 157.2 | 155.6 | 123.3 | 121.0 (+3.2) | 14.42 |
| 2023.04 | 145.4 | 146.4 | 97.6 | 122.7 (+1.7) | 13.40 |
| 2023.05 | 155.6 | 159.2 | 137.4 | 123.9 (+1.2) | 10.67 |
| 2023.06 | 161.7 | 166.8 | 160.5 | (126.3 projected, +2.4) | 8.95 |
| 2023.07 | 176.4 | 182.2 | 159.1 | (127.1 projected, +0.8) | 8.15 |
| 2023.08 | 153.7 | 157.6 | 114.8 | (128.2 projected, +1.1) | 7.19 |
| 2023.09 | 154.4 | 156.0 | 133.6 | (130.4 projected, +2.2) | 14.26 |
| 2023.10 | 142.8 | 141.9 | 99.4 | (132.2 projected, +1.8) | 8.16 |
| 2023.11 | 153.5 | 150.2 | 105.4 | (134.1 projected max SC25, +1.9) | 12.20 |
| 2023.12 | 140.3 (1) | 69.9 (2A) / 120.4 (2B) / 148.1 (2C) | (132.7 projected, -1.4) | (13.0) | |
| 2024.01 | (130.0 projected, -2.7) | ||||
| 2024.02 | (129.9 projected, -0.1) | ||||
| 2024.03 | (129.3 projected, -0.6) | ||||
| 2024.04 | (130.1 projected, +0.8) | ||||
| 2024.05 | (132.2 projected, +2.1) | ||||
| 2024.06 | (131.5 projected, -0.7) | ||||
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
Due to relatively low solar activity over the last couple of months, the possibility that solar cycle 25 has already peaked has increased significantly. Whether the first peak (and maybe solar max) will be in June or July depends on solar activity in December and early January 2024. If the average solar flux is less than 150 during this period, the first peak of solar cycle 25 using 365 day smoothing will likely be sometime between June 2 and July 9. Should the average solar flux instead become 140 then the peak date will be in early June (June 4 for solar flux, June 6 for STAR 2K SN, and June 7 for all the other sunspot numbers in the graph above). We won't know for a while yet when the final peak will be, however, it is interesting that the peak of SC25 could be as early as June 2023. The next update will likely be posted here in January 2024.
--------------------------------------------------------------------------------------
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.
