The geomagnetic field was quiet to unsettled on September 4. Solar wind speed at SOHO ranged between 349 and 485 km/sec. The high latitude magnetometer at Andenes recorded unsettled to major storm levels.
Solar flux density measured at 20h UT on 2.8 GHz was 136.0 - decreasing 22.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 153.52. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.5). Three hour interval K indices: 32111221 (planetary), 33113311 (Boulder), 43112320 (Andenes).
The background x-ray flux is at the class B8 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 230) and in 10 active regions using 1K resolution (SN: 149) SDO/HMI images.
Region 13416 [S18W52] regained the leader spot
and was quiet.
Region 13417 [S09W15] decayed slowly and was
mostly quiet. C1 flares: C1.2 @ 02:34, C1.0 @ 20:34 UT
Region 13418 [N21W02] decayed slowly and quietly.
Region 13419 [N24W63] decayed slowly and was mostly quiet. C1 flares:
C1.4 @ 15:05, C1.8 @ 22:41 UT
Region 13420 [S20E03] decayed slowly and quietly.
Region 13421 [N14E01] developed further with 2 magnetic delta
structures forming. An M class flare is possible. C1 flares: C1.3 @ 04:43,
C1.5 @ 08:54, C1.6 @ 09:44, C1.9 @ 12:54, C1.4 @ 17:18, C1.2 @ 21:29, C1.1 @
21:44 UT
New region 13422 [N15E23] emerged on September 3 and developed
further the next day as it was numbered by SWPC. C1 flares: C1.3 @ 10:20,
C1.7 @ 14:33, C1.2 @ 15:34 UT
New region 13423 [N16E63] emerged on September 3 at the northeast
limb and developed on September 4. C1 flares: C1.3 @ 19:20 UT
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S8909 [N18W18] was quiet and stable.
S8914 [S07W26] decayed slowly and quietly.
New region S8922 [N21W58] emerged with tiny spots.
New region S8923 [S12E25] emerged with a tiny spot.
AR 13413 behind the northwest limb was the likely
source of a C1.3 @ 16:00 and a C1.5 flare at 17:37 UT.
An active region behind the northeast limb was the source of a C1.0 glare at
20:04 UT
Minor update added at 15:45 UT: A weak solar wind shock was observed at DSCOVR at 14:40 UT, likely the late arrival of the September 1 CME. Unsettled to minor storm intervals are possible for the remainder of today. AR 13421 produced an M2.0 flare at 08:12 UT.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.0 | 04:43 | N14E14 | 13421 | GOES18 | |
| C2.2 | 06:19 | 13417 | GOES16 | ||
| C2.2 | 06:50 | 13421 | GOES16 | ||
| C2.1 | 07:11 | 13421 | GOES16 | ||
| C2.2 | 07:24 | 13419 | GOES16 | ||
| C6.6 | 11:06 | behind northwest limb | 13413 | GOES16 | LDE |
| C2.4 | 13:49 | spotless plage AR near southeast limb | GOES16 | ||
| C2.1 | 14:08 | 13422 | GOES16 |
September 2-4: 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]
A negative polarity northern hemisphere coronal hole (CH1168) was Earth facing on September 3. CH1168 may be too far to the north to cause geomagnetic effects.
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 mostly quiet on September 5-7. Effects from CH1168 could cause unsettled intervals on September 6.
| 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 | ||||||||||
| 13416 | 2023.08.24 2023.08.25 |
4 | 1 | S19W66 | 0007 | BXO |
 |
 |
location: S18W52 |
||
| S8900 | 2023.08.27 | N10W51 | |||||||||
| 13417 | 2023.08.28 2023.08.28 |
4 | 9 | 4 | S08W22 | 0040 | CAO | CRO |
 |
 |
location: S09W15 area: 0020 |
| 13418 | 2023.08.29 2023.08.30 |
1 | 7 | 3 | N21W04 | 0010 | HRX | CRO |
 |
 |
area: 0020 |
| S8905 | 2023.08.29 | N23W48 | |||||||||
| S8909 | 2023.08.30 | 4 | N18W18 | 0005 | BXO |
 |
 |
||||
| 13420 | 2023.08.30 2023.09.03 |
1 | 13 | 7 | S20E03 | 0020 | CRO | DRO |
 |
 |
area: 0030 SWPC classification is invalid with 1 spot |
| S8912 | 2023.08.31 | N22W37 |
 |
||||||||
| 13419 | 2023.09.01 2023.09.02 |
3 | 5 | 3 | N24W63 | 0010 | BXO | BXO |
 |
 |
area: 0015 |
| S8914 | 2023.09.01 | 3 | 1 | S07W26 | 0070 | HRX |
 |
 |
split off from AR 13417 | ||
| S8915 | 2023.09.01 | S20E23 | |||||||||
| 13421 | 2023.09.02 2023.09.03 |
9 | 32 | 14 | N15W00 | 0020 | DAI | DAC |
 |
 |
beta-delta area: 0290 location: N14E01 |
| 13422 | 2023.09.03 2023.09.04 |
6 | 16 | 8 | N13E22 | 0030 | CRO | DRI |
 |
 |
beta-gamma location: N15E23 area: 0100 |
| S8918 | 2023.09.03 | N09W48 |
 |
||||||||
| 13423 | 2023.09.03 2023.09.04 |
6 | 14 | 7 | N16E61 | 0010 | BXO | DRI |
 |
 |
beta-gamma area: 0070 location: N16E63 |
| S8921 | 2023.09.03 | S14E56 |
 |
||||||||
| S8922 | 2023.09.04 | 2 | 1 | N21W58 | 0005 | BXO |
 |
||||
| S8923 | 2023.09.04 | 1 | S12E25 | 0001 | AXX |
 |
|||||
| Total spot count: | 30 | 110 | 49 | ||||||||
| Sunspot number: | 100 | 230 | 149 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 49 | 133 | 72 | (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): | 110 | 127 | 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) | 7.3 |
| 2023.09 | 133.4 (1) | 11.3 (2A) / 84.8 (2B) / 113.9 (2C) | (140.7 projected, +3.4) | (24.4) | |
| 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.
