The geomagnetic field was quiet to active on December 16 under the influence of CME effects. Solar wind speed at SOHO ranged between 409 and 520 km/sec. The high latitude magnetometer at Andenes recorded quiet to major storm levels. A distubance related to the December 14 was in progress at DSCOVR at 07:33 UT (the exact start time is not yet clear due to a data gap after 05:56 UT) on December 17.
Solar flux density measured at 20h UT on 2.8 GHz was 149.0 - increasing 8.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.87. 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 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.0). Three hour interval K indices: 44323133 (planetary), 34222222 (Boulder), 55411054 (Andenes).
The background x-ray flux is at the class C2 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 272) and in 11 active regions using 1K resolution (SN: 168) SDO/HMI images.
Region 13513 [N18W82] was mostly quiet and
stable.
Region 13514 [N04W81] decayed further and produced many C flares. An
M class flare is possible while the region is rotating over the northwest
limb. C1 flares: C1.9 @ 07:33, C1.5 @ 12:10, C1.9 @ 12:32, C1.6 @ 18:30,
C1.6 @ 21:03 UT
Region 13516 [S18W26] decayed slowly and quietly.
Region 13517 [N14W67] reemerged with a tiny spot.
Region 13518 [N14E22] decayed slowly and
quietly.
Region 13519 [S09W02] was mostly quiet and stable. Slight decay was
observed in the leading penumbra.
Region 13520 [N08W75] was mostly quiet and stable.
Region 13521 [N11E59] was quiet and stable.
New region 13522 [S03E27] emerged on December 15 and was numbered the
next day by SWPC as the region began to decay.
New region 13523 [N21E64] rotated into view on December 15 with SWPC
numbering the region the following day.
New region 13524 [N26E65] rotated into view on December 15 and
received its NOAA number the next day.
New region 13525 [S08E36] emerged on December 15 and was numbered by
SWPC the next day.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9238 [N30E12] reemerged with tiny spots.
New region S9243 [N16E83] rotated into view with tiny spots.
New region S9244 [N09E42] was observed with tiny spots in an old
plage area. C1 flare: C1.5 @ 21:22 UT
New region S9245 [S19E79] rotated into view with a tiny spot.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C4.6 | 00:13 | 13514 | GOES16 | ||
| C2.1 | 02:12 | 13514 | GOES16 | ||
| C2.1 | 02:40 | 13514 | GOES16 | ||
| C4.0 | 03:09 | 13514 | GOES16 | ||
| C2.3 | 03:34 | 13514 | GOES16 | ||
| C3.6 | 05:46 | 13514 | GOES16 | ||
| C2.2 | 06:51 | 13514 | GOES16 | ||
| C2.3 | 07:53 | 13514 | GOES16 | ||
| C2.1 | 09:09 | 13514 | GOES16 | ||
| C2.6 | 11:07 | 13514 | GOES16 | ||
| C2.5 | 11:15 | 13514 | GOES16 | ||
| C2.6 | 11:33 | 13513 | GOES16 | ||
| C2.1 | 13:10 | 13514 | GOES16 | ||
| C8.3 | 13:54 | 13514 | GOES16 | LDE | |
| C7.7 | 14:36 | 13514 | GOES16 | ||
| C5.2 | 15:20 | 13514 | GOES16 | ||
| C3.0 | 15:54 | 13514 | GOES16 | ||
| C2.3 | 16:43 | 13514 | GOES16 | ||
| C2.1 | 17:35 | 13514 | GOES16 | ||
| C2.7 | 17:44 | 13514 | GOES16 | ||
| C2.0 | 19:22 | 13514 | GOES16 | ||
| C3.2 | 19:55 | 13514 | GOES16 | ||
| C2.1 | 22:21 | 13514 | GOES16 |
December 14: An asymmetric full halo CME was observed after the X2.8
flare in AR 13514. The CME reached Earth on December 17.
December 15: A partial halo CME was observed after the M6 flares AR 13514. The CME could reach Earth on December 18 and
unsettled and active intervals.
December 16: 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 to very poor. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to major storm on December 17 due to effects from the December 14 CME. Effects from CH1193 could reach Earth late on December 17 and cause quiet to minor storm conditions until December 19. The December 15 CME could reach Earth on December 18 and contribute to the ongoing 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 | ||||||||||
| 13513 | 2023.12.04 2023.12.05 |
1 | 1 | 1 | N18W82 | 0079 | HSX | HSX |
 |
 |
|
| 13514 | 2023.12.05 2023.12.06 |
12 | 11 | 6 | N05W82 | 0300 | EKC | EAC |
 |
 |
beta-gamma location: N04W81 |
| 13516 | 2023.12.08 2023.12.08 |
1 | 12 | 4 | S18W29 | 0010 | AXX | BXO |
 |
 |
location: S18W26 area: 0020 |
| 13515 | 2023.12.08 2023.12.08 |
S14W31 | |||||||||
| 13517 | 2023.12.08 2023.12.11 |
1 | N11W69 | 0002 | AXX |
 |
location: N14W67 | ||||
| S9222 | 2023.12.08 | N13W58 | |||||||||
| 13518 | 2023.12.12 2023.12.12 |
3 | 7 | 2 | N13E21 | 0010 | AXX | BXO |
 |
 |
location: N14E22 |
| S9232 | 2023.12.12 | S19W40 | |||||||||
| 13519 | 2023.12.12 2023.12.13 |
18 | 38 | 26 | S12W02 | 0130 | DAI | DSI |
 |
 |
location: S09W02 area: 0200 |
| S9234 | 2023.12.12 | S18W48 | |||||||||
| 13520 | 2023.12.13 2023.12.13 |
5 | 6 | 4 | N08W75 | 0080 | CSO | DSO |
 |
 |
area: 0110 |
| 13521 | 2023.12.14 2023.12.15 |
1 | 4 | 2 | N12E57 | 0020 | HSX | HSX |
 |
 |
area: 0060 location: N11E59 |
| S9238 | 2023.12.14 | 3 | N30E12 | 0006 | AXX |
 |
|||||
| 13523 | 2023.12.15 2023.12.16 |
2 | 2 | 1 | N21E62 | 0020 | HRX | HRX |
 |
 |
|
| 13525 | 2023.12.15 2023.12.16 |
4 | 10 | 6 | S09E45 | 0020 | BXO | DRO |
 |
 |
location: S09E46 area: 0045 |
| 13522 | 2023.12.15 2023.12.16 |
4 | 5 | 3 | S04E25 | 0010 | BXO | BXO |
 |
 |
location: S03E27 |
| 13524 | 2023.12.15 2023.12.16 |
2 | 4 | 3 | N26E63 | 0020 | HRX | HRX |
 |
 |
location: N26E65 area: 0030 |
| S9243 | 2023.12.16 | 2 | N16E83 | 0010 | AXX |
 |
|||||
| S9244 | 2023.12.16 | 5 | N09E42 | 0007 | BXO |
 |
|||||
| S9245 | 2023.12.16 | 1 | S19E79 | 0002 | AXX |
 |
|||||
| Total spot count: | 53 | 112 | 58 | ||||||||
| Sunspot number: | 163 | 272 | 168 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 89 | 146 | 92 | (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): | 179 | 150 | 134 | ||||||||
| 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 | 138.0 (1) | 61.4 (2A) / 118.9 (2B) / 139.5 (2C) | (132.7 projected, -1.4) | (10.9) | |
| 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.
