The geomagnetic field was quiet to unsettled on December 13. Solar wind speed at SOHO ranged between 333 and 399 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. Another disturbance was observed arriving at SOHO at 21:57 UT and has since caused unsettled to minor storm conditions.
Solar flux density measured at 20h UT on 2.8 GHz was 134.8 - increasing 16.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.01. 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 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.1). Three hour interval K indices: 12111323 (planetary), 12222322 (Boulder), 22111345 (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 8 active regions using 2K resolution (SN: 192) and in 8 active regions using 1K resolution (SN: 148) SDO/HMI images.
Region 13513 [N18W42] decayed further and was
mostly quiet. C1 flares: C1.8 @ 18:15 UT
Region 13514 [N06W41] developed further gaining spots and area. The
region is compact and has magnetic delta structures. A major flare is
possible. C1 flares: C1.2 @ 06:53, C1.0 @ 07:56, C1.1 @ 08:36, C1.2 @ 11:31,
C1.8 @ 13:50 , C1.3 @ 17:38, C1.5 @ 20:07, C1.7 @ 20:21, C1.3 @ 21:21, C1.5
@ 23:21 UT
Region 13516 [S15E11] was merged with AR 13515 as both the leading
and trailing polarity fields have merged.
Region 13517 [N16W27] decayed slowly and quietly.
Region 13518 [N12E60] was quiet and stable.
New region 13519 [S10E37] emerged on December 12 and was numbered the
next day as slow development continued. C1 flares: C1.1 @ 10:45 UT
New region 13520 [N10W32] emerged with several spots between ARs
13517 and 13514. C flares are possible. C1 flares: C1.2 @ 04:28 UT
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9222 [N13W19] was quiet and stable.
New region S9232 [S19E12] emerged early in the day, then
decayed slowly after noon.
New region S9233 [S11E51] emerged after noon
with several tiny spots.
New region S9234 [S18E04] emerged with a tiny spot.
AR 13511 behind the southwest limb was the likely source of a C1.4 flare at 03:00 UT
Minor update added at 18:40 UT: AR 13514 produced a major X2.8 flare at 17:02 UT. It is not yet known if there was a CME associated with this event.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.1 | 14:37 | 13514 | GOES18 | ||
| C9.5 | 15:21 | southwest limb | 13511 | GOES18 |
December 11-12: No obviously Earth directed CMEs were observed.
December 13: A faint partial halo CME was observed early in the day,
likely associated with a C2.8 flare in AR 13514 at 22:55 UT on December 12.
The CME could reach Earth on December 15.
[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 trans equatorial positive polarity coronal hole (CH1192) rotated across the central meridian on December 11-13. Significant decay was observed on December 12-13 due to the development of ARs 13514 and 13517. A positive polarity northern hemisphere coronal hole (CH1193) will be Earth facing on December 15-16.
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 14-15 due to effects from CH1192. Quiet to active is possible on December 16 due to effects from the December 12/13 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 |
Magnetic (SDO) |
SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 13512 | 2023.12.03 2023.12.04 |
S09W66 |
location: S08W60 |
||||||||
| 13513 | 2023.12.04 2023.12.05 |
5 | 7 | 4 | N18W41 | 0180 | CAO | CAO |
 |
 |
location: N18W42 |
| 13514 | 2023.12.05 2023.12.06 |
5 | 46 | 28 | N07W36 | 0050 | DAI | DKC |
 |
 |
beta-gamma-delta location: N06W41 area: 0520 |
| 13516 | 2023.12.08 2023.12.08 |
3 | 11 | 4 | S18E11 | 0010 | AXX | CRO |
 |
 |
location: S15E11 merged with AR 13515 area: 0030 |
| 13515 | 2023.12.08 2023.12.08 |
2 | S14E08 | 0030 | HRX |
 |
|||||
| 13517 | 2023.12.08 2023.12.11 |
3 | 5 | 3 | N15W28 | 0010 | CRO | CRO |
 |
 |
location: N16W27 area: 0020 |
| S9222 | 2023.12.08 | 1 | 1 | N13W19 | 0005 | AXX |
 |
 |
|||
| S9224 | 2023.12.08 | S00W38 | |||||||||
| S9225 | 2023.12.09 | N05W37 | |||||||||
| 13518 | 2023.12.12 2023.12.12 |
1 | 3 | 2 | N12E61 | 0040 | HSX | HAX |
 |
 |
area: 0070 location: N12E60 |
| S9232 | 2023.12.12 | S19W01 |
 |
||||||||
| 13519 | 2023.12.12 2023.12.13 |
4 | 25 | 17 | S11E38 | 0020 | DAO | DAI |
 |
 |
location: S10E37 area: 0220 |
| S9234 | 2023.12.12 | S18W09 |
 |
||||||||
| 13520 | 2023.12.13 2023.12.13 |
11 | 14 | 9 | N10W34 | 0210 | CAO | DAO |
 |
was AR S9236 | |
| Total spot count: | 34 | 112 | 68 | ||||||||
| Sunspot number: | 114 | 192 | 148 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 65 | 148 | 104 | (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): | 125 | 106 | 118 | ||||||||
| 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 | 135.9 (1) | 47.8 (2A) / 114.1 (2B) / 132.8 (2C) | (132.7 projected, -1.4) | (10.3) | |
| 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.
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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.
