The geomagnetic field was quiet on September 11. Solar wind speed at SOHO ranged between 336 and 442 km/sec, probably under the influence of a low speed stream from CH1170. The high latitude magnetometer at Andenes recorded quiet to unsettled levels.
Solar flux density measured at 20h UT on 2.8 GHz was 176.4 - increasing 18.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 154.05. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.1). Three hour interval K indices: 12111112 (planetary), 22113222 (Boulder), 21022123 (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: 319) and in 13 active regions using 1K resolution (SN: 215) SDO/HMI images.
Region 13423 [N15W28] decayed in the leading
spot section and was otherwise mostly unchanged. M class flaring is
possible. C1 flares: C1.9 @ 13:17 UT
Region 13425 [N23E02] developed in the trailing spot section and
gained a magnetic delta structure. M class flaring is possible. C1 flares:
C1.7 @ 13:57 UT
Region 13427 [S28E02] decayed slowly and quietly.
Region 13428 [N14W63] decayed slowly and quietly.
Region 13429 [N11E46] gained spots, however none of the spots have
mature penumbra. The region has polarity intermixing and produced the
largest flare of the day.
Region 13430 [S17W03] developed slowly and quietly.
Region 13431 [S07E47] decayed after producing many flares, including
2 M flares. The magnetic delta disappeared.
New region 13432 [S22W73] emerged on September 8 and was numbered by
SWPC 3 days later as the region approached the southwest limb.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S8935 [N30W18] reemerged with tiny spots.
S8940 [S22E41] was quiet and stable.
S8942 [N07E53] was quiet and stable.
S8949 [N09E32] decayed slowly and quietly.
S8950 [N28E77] rotated fully into view with a
mature spot.
New region S8952 [S16W24] emerged before noon, then decayed slowly.
New region S8954 [N17E57] emerged with tiny spots.
New region S8955 [N31E28] was observed with tiny spots in an
old plage area.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C3.6 | 00:40 | 13421 | GOES16 | ||
| M1.3/1F | 01:28 | N08E62 | 13429 | GOES16 | CME, moderate type II radio sweep |
| C2.1 | 03:42 | 13431 | GOES16 | simultaneous flare in AR 13425 | |
| M1.1 | 04:07 | S09E59 | 13431 | GOES16 | |
| C2.6 | 04:36 | 13431 | GOES18 | ||
| C7.2 | 05:42 | 13431 | GOES18 | ||
| C4.5 | 05:48 | 13421 | GOES16 | ||
| C9.3/1N | 06:01 | S04E55 | 13431 | GOES16 | |
| C6.8 | 06:17 | 13431 | GOES16 | ||
| C3.5 | 06:56 | 13431 | GOES16 | ||
| C2.1 | 07:30 | 13431 | GOES16 | ||
| C2.7 | 10:12 | 13423 | GOES16 | ||
| C7.4 | 10:37 | 13431 | GOES16 | ||
| C4.0 | 11:03 | 13423 | GOES16 | ||
| C3.7/1F | 11:27 | S04E53 | 13431 | GOES16 | |
| C2.3 | 12:17 | 13425 | GOES16 | simultaneous flares in AR 13429 and 13431 | |
| M1.1 | 14:49 | S04E50 | 13431 | GOES16 | |
| C2.4 | 17:07 | 13423 | GOES16 | ||
| C5.5 | 17:35 | N21E09 | 13425 | GOES16 | simultaneous flare in AR 13431 |
| C2.5 | 18:25 | 13425 | GOES16 | ||
| C2.9 | 18:35 | 13423 | GOES16 | ||
| C3.3 | 18:49 | 13425 | GOES16 | simultaneous flare in AR 13421 | |
| C3.4 | 19:50 | 13421 | GOES16 | simultaneous flare in AR 13425 | |
| C8.2 | 21:14 | 13425 | GOES16 | ||
| C2.3 | 23:23 | 13431 | GOES16 |
September 9-11: No obviously Earth directed CMEs were 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]
Northern hemisphere positive polarity coronal holes (CH1169 and CH1170) rotated across the central meridian on September 8-10. A negative polarity coronal hole (CH1171) in the southern hemisphere was Earth facing on September 9-10. A trans equatorial negative polarity coronal hole (CH1172) will be Earth facing on September 11-13.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is fair to good. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to active on September 12-15 due to effects from CH1169, CH1171 and CH1172.
| 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 | ||||||||||
| 13418 | 2023.08.29 2023.08.30 |
1 | N20W93 | 0020 | HRX |
 |
rotated out of view | ||||
| 13421 | 2023.09.02 2023.09.03 |
4 | N15W91 | 0010 | BXO |
 |
rotated out of view |
||||
| 13422 | 2023.09.03 2023.09.04 |
N14W75 |
location: N11W71 |
||||||||
| 13423 | 2023.09.03 2023.09.04 |
21 | 39 | 19 | N16W30 | 0420 | EKC | EKI |
 |
 |
area: 0610 location: N15W28 |
| S8921 | 2023.09.03 | S14W35 | |||||||||
| 13424 | 2023.09.05 2023.09.05 |
N17W06 |
 |
location: N18W00 |
|||||||
| S8926 | 2023.09.05 | N23W54 | |||||||||
| 13425 | 2023.09.05 2023.09.06 |
24 | 43 | 21 | N23E02 | 0100 | EAI | DAI |
 |
 |
beta-gamma-delta area: 0230 location: N23E15 |
| S8928 | 2023.09.05 | S22W33 | |||||||||
| S8931 | 2023.09.06 | N09W51 | |||||||||
| S8933 | 2023.09.06 | S18W57 | |||||||||
| S8934 | 2023.09.06 | S22E17 | |||||||||
| 13426 | 2023.09.07 2023.09.07 |
S14W42 |
 |
location: S17W37 | |||||||
| S8935 | 2023.09.07 | 2 | 1 | N30W18 | 0004 | AXX |
 |
||||
| 13427 | 2023.09.07 2023.09.09 |
3 | 8 | 3 | S27E02 | 0010 | BXO | CRO |
 |
 |
location: S28E02 area: 0020 |
| S8937 | 2023.09.07 | N11W16 | |||||||||
| 13432 | 2023.09.08 2023.09.11 |
3 | 6 | 3 | S24W74 | 0010 | BXO | CRO |
 |
 |
location: S22W73 area: 0020 |
| S8940 | 2023.09.08 | 2 | S22E41 | 0003 | BXO |
 |
 |
||||
| 13429 | 2023.09.09 2023.09.10 |
4 | 13 | 10 | N10E46 | 0030 | DRO | DRI |
 |
 |
beta-gamma area: 0060 location: N11E46 |
| S8942 | 2023.09.09 | 1 | 1 | N07E53 | 0050 | HSX |
 |
 |
|||
| 13428 | 2023.09.09 2023.09.10 |
1 | 3 | 2 | N14W62 | 0005 | AXX | AXX |
 |
 |
|
| 13431 | 2023.09.09 2023.09.10 |
5 | 12 | 8 | S07E47 | 0050 | DAO | DAI |
 |
 |
beta-gamma area: 0130 |
| S8945 | 2023.09.09 | N27E26 | |||||||||
| 13430 | 2023.09.10 2023.09.10 |
7 | 22 | 14 | S16W05 | 0030 | CRO | DRI |
 |
 |
area: 0120 location: S17W03 |
| S8948 | 2023.09.10 | N08E24 |
 |
||||||||
| S8949 | 2023.09.10 | 2 | N09E32 | 0004 | AXX |
 |
 |
||||
| S8950 | 2023.09.10 | 1 | 1 | N28E77 | 0170 | HSX |
 |
 |
|||
| S8952 | 2023.09.11 | 1 | 1 | S16W24 | 0002 | AXX |
 |
||||
| S8954 | 2023.09.11 | 2 | 1 | N17E57 | 0005 | BXO |
 |
||||
| S8955 | 2023.09.11 | 2 | N31E28 | 0004 | AXX |
 |
|||||
| Total spot count: | 73 | 159 | 85 | ||||||||
| Sunspot number: | 173 | 319 | 215 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 102 | 201 | 127 | (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): | 190 | 175 | 172 | ||||||||
| 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 | 149.7 (1) | 43.6 (2A) / 118.9 (2B) / 120.7 (2C) | (140.7 projected, +3.4) | (11.0) | |
| 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.
