The geomagnetic field was quiet to unsettled on September 17 under the influence of weak CME effects. Solar wind speed at SOHO ranged between 389 and 507 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 144.6 - decreasing 4.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 154.08. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 15 (STAR Ap - based on the mean of three hour interval ap indices: 14.6). Three hour interval K indices: 33333233 (planetary), 33333333 (Boulder), 45213355 (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 12 active regions using 2K resolution (SN: 208) and in 11 active regions using 1K resolution (SN: 159) SDO/HMI images.
Region 13425 [N24W73] decayed further and had
only 2 tiny spots left by the end of the day.
Region 13429 [N11W38] decayed further and was mostly quiet.
Region 13433 [N28W00] was quiet and stable.
Region 13434 [N08W27] was quiet and stable.
Region 13435 [N09E68] has a small magnetic delta structure in the
southern part of the largest penumbra. M class flaring is possible. C1
flares: C1.3 @ 06:55, C1.3 @ 10:37, C1.2 @ 23:56 UT
New region 13436 [N19W21] emerged with many small and tiny spots. C
flares are possible.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S8961 [S13W36] was quiet and stable.
S8964 [N23W67] developed quickly after noon and could produce C
flares.
S8968 [N20W00] was quiet and stable.
New region S8971 [S24E72] rotated into view with small spots.
New region S8972 [S18W01] emerged with tiny spots.
New region S8973 [N18E86] rotated partly into view with a mature
spot.
AR 13423 behind the northwest limb was the likely source of a C1.2 flare at 12:58 UT
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C3.5 | 16:04 | 13435 | GOES16 | weak type II radio sweep |
September 15, 17: No obviously Earth directed CMEs were observed.
September 16: A CME was observed just after 09h UT due
to an extensive filament eruption across the central meridian. The full halo
CME will probably reach Earth on September 19.
[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]
Several coronal holes formed after the extensive filament eruption on September 16. CH1173 is a positive polarity trans equatorial coronal hole and was Earth facing on September 16. Positive polarity coronal hole CH1174 formed in the northern hemisphere on September 16 and rotated across the central meridian on September 16-17. A negative polarity trans equatorial coronal hole (CH1174) will likely become Earth facing on September 19.
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 to fair.
The geomagnetic field is expected to be quiet to minor storm on September 18 due to the September 14 CME. Quiet to major storm conditions are possible on September 19-20 when the September 16 CME reaches Earth. Effects from CH1173 and CH1174 are possible on September 20 and could extend into September 21. On September 22 a high speed stream from CH1175 will likely arrive and cause quiet to active conditions.
| 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 | ||||||||||
| 13425 | 2023.09.05 2023.09.06 |
6 | 2 | 1 | N23W75 | 0020 | CAO | AXX |
 |
 |
location: N24W73 area: 0003 |
| 13427 | 2023.09.07 2023.09.09 |
S27W82 | location: S29W76 | ||||||||
| S8940 | 2023.09.08 | S22W37 | |||||||||
| 13429 | 2023.09.09 2023.09.10 |
13 | 22 | 13 | N11W36 | 0060 | CAO | DAI |
 |
 |
area: 0100 |
| 13434 | 2023.09.09 2023.09.15 |
3 | 2 | N08W28 | 0006 | BXO |
 |
 |
|||
| 13431 | 2023.09.09 2023.09.10 |
1 | S14W38 | 0000 | AXX |
the previous SWPC location was S08W23 location: S10W30 |
|||||
| S8945 | 2023.09.09 | N27W52 | |||||||||
| 13430 | 2023.09.10 2023.09.10 |
S17W88 |
 |
|
|||||||
| S8948 | 2023.09.10 | N12W58 | |||||||||
| 13433 | 2023.09.10 2023.09.12 |
3 | 9 | 5 | N28W04 | 0090 | CAO | CSO |
 |
 |
area: 0120 location: N28W00 |
| S8954 | 2023.09.11 | N15W11 | |||||||||
| S8955 | 2023.09.11 | N23W54 | |||||||||
| S8958 | 2023.09.12 | S24W56 | |||||||||
| S8960 | 2023.09.13 | S13W40 |
 |
||||||||
| S8961 | 2023.09.13 | 1 | S13W36 | 0001 | AXX |
 |
 |
||||
| S8963 | 2023.09.13 | N18W41 | |||||||||
| S8964 | 2023.09.14 | 10 | 4 | N23W67 | 0190 | CAO |
 |
 |
|||
| S8965 | 2023.09.15 | S19W48 |
 |
||||||||
| S8966 | 2023.09.15 | S07E51 |
 |
||||||||
| 13435 | 2023.09.16 2023.09.16 |
3 | 7 | 4 | N10E60 | 0110 | DAO | DKO |
 |
 |
beta-delta area: 0480 location: N09E68 |
| S8968 | 2023.09.16 | 7 | 2 | N20W00 | 0015 | AXX |
 |
 |
|||
| 13436 | 2023.09.17 2023.09.17 |
8 | 17 | 11 | N19W22 | 0080 | CAO | DRI |
 |
was AR S8970 area: 0120 |
|
| S8971 | 2023.09.17 | 4 | 2 | S24E72 | 0050 | DAO |
 |
||||
| S8972 | 2023.09.17 | 5 | 4 | S18W01 | 0015 | CRO |
 |
||||
| S8973 | 2023.09.17 | 1 | 1 | N18E86 | 0110 | HSX |
 |
||||
| Total spot count: | 34 | 88 | 49 | ||||||||
| Sunspot number: | 94 | 208 | 149 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 59 | 129 | 90 | (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): | 103 | 114 | 119 | ||||||||
| 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 |
| 2022.02 | 109.1 | 106.5 | 60.9 | 64.7 (+4.6) | 10.46 |
| 2022.03 | 117.0 | 115.8 | 78.6 | 68.7 (+4.0) | 10.20 |
| 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 | 101.1 (+2.2) | 9.33 |
| 2022.12 | 147.9 | 143.4 | 112.8 | 106.7 (+5.6) | 10.99 |
| 2023.01 | 182.4 | 176.6 | 144.4 | 113.4 (+6.7) | 8.73 |
| 2023.02 | 167.2 | 163.2 | 111.3 | 117.9 (+3.5) | 14.48 (current SC25 peak) |
| 2023.03 | 157.2 | 155.6 | 123.3 | (121.0 projected, +3.1) | 14.42 |
| 2023.04 | 145.4 | 146.4 | 96.4 | (126.3 projected, +5.3) | 13.40 |
| 2023.05 | 155.6 | 159.2 | 137.9 | (131.9 projected, +5.6) | 10.67 |
| 2023.06 | 161.7 | 166.8 | 163.4 | (135.1 projected, +3.2) | 8.95 |
| 2023.07 | 176.4 | 182.2 | 159.1 | (135.5 projected, +0.4) | 8.15 |
| 2023.08 | 153.7 | 157.6 | 114.9 | (137.3 projected, +1.8) | 7.19 |
| 2023.09 | 147.8 (1) | 64.9 (2A) / 114.5 (2B) / 115.2 (2C) | (140.7 projected, +3.4) | (12.1) | |
| 2023.10 | (142.5 projected, +1.8) | ||||
| 2023.11 | (145.1 projected max SC25, +2.6) | ||||
| 2023.12 | (144.2 projected, -0.9) | ||||
| 2024.01 | (141.4 projected, -2.8) | ||||
| 2024.02 | (141.2 projected, -0.2) | ||||
| 2024.03 | (140.8 projected, -0.4) | ||||
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
Looking back 6 months, the 365d smoothed values for solar flux and all sunspot numbers with the exception of NOAA's, are all above their solar cycle 24 peak. The first peak of solar cycle 25 is forecast to be between July 7 and 10, 2023 (solar flux on July 7, ISN and STAR 1K and 2K all have that peak on July 9, while NOAA peaks on July 10). This is unlikely to be the final peak of SC25, however, there is a small probability that it is the actual sunspot and solar flux maximum.
--------------------------------------------------------------------------------------
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.
