The geomagnetic field was very quiet on April 25. The high latitude magnetometer at Andenes recorded quiet to unsettled levels. The above 10 MeV proton flux was at background levels at the end of the day. A high speed stream associated with CH1215 reached DSCOVR early on April 26.
Solar flux density measured at 20h UT on 2.8 GHz was 166.7 - decreasing 0.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.67. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.71 on June 27, 2023). The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.6). Three hour interval K indices: 00010001 (planetary), 01012311 (Boulder), 00011013 (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 24 active regions using 2K resolution (SN: 431) and in 19 active regions using 1K resolution (SN: 271) SDO/HMI images.
Region 13639 [N29W76] decayed slowly and
quietly retaining only a single small spot at the end of the day.
Region 13643 [S11W79] decayed slowly as the spot group rotated to the
southwest limb.
Region 13644 [N12W46] decayed slowly and quietly.
Region 13646 [N22W34] decayed slowly and was mostly quiet.
Region 13647 [S14W85] decayed slowly and rotated to the southwest
limb.
Region 13648 [N18W59] decayed and lost the magnetic delta.
Region 13652 [N13W28] was quiet and stable.
Region 13653 [N03E02] was quiet and stable.
Region 13654 [S07E02] gained spots and was mostly quiet. The region
has polarity intermixing and an M class flare is possible.
Region 13655 [S27E07] decayed slowly and quietly.
Region 13656 [S12E20] decayed slowly and quietly.
Region 13657 [S13W10] decayed slowly and quietly.
Region 13658 [S21W49] decayed slowly and
quietly.
New region 13659 [S13E35] emerged on April 24 and was numbered the
next day by SWPC.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9600 [N14W40] decayed slowly and quietly.
S9622 [S16W26] reemerged with tiny spots.
S9627 [S15W04] was mostly quiet and stable.
S9630 [S11E09] was mostly quiet and stable.
New region S9635 [S23W42] emerged to the southeast of AR 13658 with
several spots.
New region S9636 [S06W34] emerged with a tiny spot.
S9637 [S10E64] was observed with tiny spots in an old
plage area.
New region S9638 [N04E43] emerged with a tiny spot.
New region S9639 [N05E62] emerged with a tiny
spot.
New region S9640 [N09W09] emerged with a tiny spot.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C4.7 | 00:17 | 13645 | GOES16 | simultaneous flare in AR 13639 | |
| C4.3 | 00:31 | 13643 | GOES16 | ||
| C3.6 | 00:43 | 13643 | GOES16 | ||
| C4.7 | 01:22 | 13648 | GOES16 | ||
| C8.7 | 01:35 | S10W73 (SDO/AIA) | 13643 | GOES16 | |
| M1.0 | 01:49 | 13643 | GOES16 | flare in AR 13645 made a contribution after 02:05 | |
| M1.0 | 02:43 | 13643 | GOES16 | ||
| M1.0 | 03:14 | 13643 | GOES16 | simultaneous flare in AR 13648 | |
| C7.1 | 04:38 | 13648 | GOES16 | ||
| C2.4 | 06:46 | S14E07 (SDO/AIA) | S9627 | GOES16 | |
| C2.3 | 07:09 | 13643 | GOES16 | ||
| C2.1 | 07:55 | 13643 | GOES16 | ||
| C2.8 | 08:14 | 13638 | GOES16 | ||
| C2.1 | 09:34 | 13643 | GOES16 | ||
| C2.6 | 12:02 | 13647 | GOES16 | ||
| C4.3 | 12:35 | 13645 | GOES16 | ||
| C4.4 | 13:07 | 13638 | GOES16 | ||
| M1.0 | 13:21 | 13638 | GOES16 | ||
| C3.7 | 14:31 | 13654 | GOES16 | ||
| C2.4 | 16:04 | 13643 | GOES16 | ||
| C3.2 | 16:32 | 13645 | GOES16 | simultaneous flare in AR 13648 | |
| M1.3 | 17:12 | 13638 | GOES16 | ||
| C9.4 | 18:07 | 13638 | GOES16 | ||
| C3.4 | 19:12 | 13638 | GOES16 | ||
| C2.5 | 20:27 | 13643 | GOES16 | ||
| C3.2 | 22:29 | 13638 | GOES16 | ||
| C3.2 | 23:10 | 13654 | GOES16 |
April 23-25: 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 positive polarity recurrent trans equatorial coronal hole (CH1215) was Earth facing on April 22-23. A positive polarity southern hemisphere coronal hole (CH1216) was Earth facing on April 23-24. A recurrent negative polarity trans equatorial coronal hole (CH1217) will likely rotate across the central meridian on April 27-28.
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 active on April 26-27 due to effects from CH1215 and CH 1216. Quiet to unsettled is likely on April 28.
| 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 | ||||||||||
| 13639 | 2024.04.13 2024.04.14 |
2 | 1 | 1 | S30W78 | 0020 | CAO | AXX |
 |
 |
location: N29W76 area: 0008 |
| 13643 | 2024.04.15 | 5 | 21 | 8 | S12W72 | 0020 | CAO | DAI |
 |
 |
location: S11W79 area: 0160 |
| 13644 | 2024.04.16 2024.04.16 |
2 | 4 | 2 | N13W42 | 0040 | HSX | HRX |
 |
 |
location: N12W46 area: 0025 |
| 13646 | 2024.04.16 2024.04.17 |
9 | 19 | 10 | N21W40 | 0130 | DAO | EAO |
 |
 |
locaton: N22W34 |
| S9600 | 2024.04.16 | 2 | 1 | N14W40 | 0025 | HAX |
 |
 |
|||
| 13650 | 2024.04.16 2024.04.19 |
S11W59 | location: S11W60 | ||||||||
| 13648 | 2024.04.17 2024.04.18 |
8 | 19 | 9 | N18W60 | 0080 | DAI | EAI |
 |
 |
beta-gamma location: N18W59 |
| 13645 | 2024.04.17 2024.04.17 |
12 | S08W84 | 0130 | DAI |
 |
location: S08W92 rotated out of view |
||||
| 13647 | 2024.04.17 2024.04.18 |
8 | 2 | 1 | S13W82 | 0120 | DAC | HAX |
 |
 |
area: 0090 location: S14W85 |
| 13651 | 2024.04.18 2024.04.19 |
N09W49 | location: N12W52 | ||||||||
| S9612 | 2024.04.19 2024.04.21 |
S20W08 | |||||||||
| 13657 | 2024.04.19 | 3 | 5 | S13W05 | 0030 | BXO | BXO |
 |
 |
location: S13W10 area: 0008 |
|
| 13652 | 2024.04.19 2024.04.20 |
1 | 10 | 2 | N14W26 | 0080 | HSX | CSO |
 |
 |
area: 0120 locaton: N13W28 |
| 13654 | 2024.04.20 2024.04.21 |
12 | 28 | 13 | S08E06 | 0210 | EAI | EHI |
 |
 |
location: S07E02 area: 0320 |
| 13653 | 2024.04.20 2024.04.21 |
3 | 1 | N03W00 | 0006 | BXO |
 |
 |
location: N03E02 | ||
| 13655 | 2024.04.21 | 4 | 12 | 5 | S27E11 | 0120 | DSO | EAO |
 |
 |
location: S27E07 |
| 13656 | 2024.04.21 2024.04.21 |
1 | 5 | 1 | S12E20 | 0010 | AXX | CRO |
 |
 |
|
| 13658 | 2024.04.22 2024.04.24 |
3 | 5 | 2 | S21W47 | 0020 | CRO | CRO |
 |
 |
location: S23W42 |
| S9622 | 2024.04.22 | 3 | 2 | S16W26 | 0007 | AXX |
 |
||||
| S9623 | 2024.04.22 | S44W54 |
reversed polarities |
||||||||
| S9625 | 2024.04.23 | S43W09 | reversed polarities | ||||||||
| S9626 | 2024.04.23 | S00E17 | |||||||||
| S9627 | 2024.04.23 | 7 | 3 | S15W04 | 0015 | DRO |
 |
 |
|||
| S9628 | 2024.04.23 | N19W08 | |||||||||
| S9629 | 2024.04.23 | S04W21 | |||||||||
| S9630 | 2024.04.24 | 20 | 10 | S11E09 | 0060 | DRO |
 |
 |
|||
| 13659 | 2024.04.24 2024.04.25 |
1 | 7 | 2 | S13E35 | 0010 | AXX | CRO |
 |
 |
|
| S9634 | 2024.04.24 | N33W21 |
 |
||||||||
| S9635 | 2024.04.25 | 10 | 7 | S23W42 | 0070 | DRO |
 |
||||
| S9636 | 2024.04.25 | 1 | S06W34 | 0002 | AXX |
 |
|||||
| S9637 | 2024.04.25 | 4 | S10E54 | 0005 | BXO |
 |
 |
||||
| S9638 | 2024.04.25 | 1 | N04E43 | 0001 | AXX |
 |
|||||
| S9639 | 2024.04.25 | 1 | 1 | N05E62 | 0002 | AXX |
 |
||||
| S9640 | 2024.04.25 | 1 | N09W09 | 0002 | AXX |
 |
|||||
| Total spot count: | 71 | 191 | 81 | ||||||||
| Sunspot number: | 211 | 431 | 271 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 134 | 257 | 147 | (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): | 232 | 237 | 217 | ||||||||
| 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 |
| 2022.09 | 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 | 121.1 (+3.3) | 14.42 |
| 2023.04 | 145.4 | 146.4 | 97.6 | 122.9 (+1.8) | 13.40 |
| 2023.05 | 155.6 | 159.2 | 137.4 | 124.1 (+1.2) | 10.67 |
| 2023.06 | 161.7 | 166.8 | 160.5 | 125.2 (+1.1) (SC25 solar max candidate) |
8.95 |
| 2023.07 | 176.4 | 182.2 | 160.0 | 124.3 (-0.9) | 8.15 |
| 2023.08 | 153.7 | 157.6 | 114.8 | 124.0 (-0.3) | 7.19 |
| 2023.09 | 154.4 | 156.0 | 134.2 | 123.8 (-0.2) | 14.26 |
| 2023.10 | 142.8 | 141.9 | 99.4 | (123.8 projected, 0.0) | 8.16 |
| 2023.11 | 153.5 | 150.2 | 105.4 | (123.5 projected, -0.3) | 12.20 |
| 2023.12 | 151.1 | 146.4 | 114.2 | (120.1 projected, -3.4) | 9.60 |
| 2024.01 | 164.6 | 159.3 | 123.0 | (116.8 projected, -3.3) | 5.46 |
| 2024.02 | 172.5 | 168.3 | 124.6 | (116.0 projected, -0.8) | 5.31 |
| 2024.03 | 154.4 | 152.9 | 104.9 | (115.4 projected, -0.6) | 11.03 |
| 2024.04 | 165.1 (1) | 122.5 (2A) / 147.0 (2B) / 154.0 (2C) | (115.4 projected, -0.0) | (9.3) | |
| 2024.05 | (116.6 projected, +1.2) | ||||
| 2024.06 | (115.8 projected, -0.8) | ||||
| 2024.07 | (114.1 projected, -1.7) | ||||
| 2024.08 | (112.1 projected, -2.0) | ||||
| 2024.09 | (110.9 projected, -1.2) | ||||
| 2024.10 | (110.3 projected, -0.6) | ||||
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
Solar activity saw a significant decrease during the latter half of February and the first part of March. While there is still a chance that there could be another and higher peak in October or November 2023, chances that June 2023 was solar max has increased. After November 2023 there is currently no other obvious candidate solar max month. Taking into account the state of the solar polar fields another major peak during SC25 is becoming less likely.
--------------------------------------------------------------------------------------
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.
