The geomagnetic field was quiet to unsettled on April 15. A disturbance was observed reaching DSCOVR at 17:28 UT, likely the arrival of the April 12 CME. There was a minor sudden increase in solar wind speed and density as well as the total field of the IMF. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at background levels at the end of the day.
Solar flux density measured at 20h UT on 2.8 GHz was 191.9 - increasing 23.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.84. 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 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.8). Three hour interval K indices: 21110123 (planetary), 12012423 (Boulder), 31112455 (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 15 active regions using 2K resolution (SN: 307) and in 11 active regions using 1K resolution (SN: 190) SDO/HMI images.
Region 13633 [S08W51] was quiet and stable.
Region 13634 [N27W42] decayed in the trailing spot section and lost
the magnetic delta structure.
Region 13635 [N20W15] decayed slowly and quietly.
Region 13636 [S21E22] was mostly quiet and stable.
Region 13637 [S13E55] developed in the trailing spot section (SWPC
split the new spots off into AR 13643). A
magnetic delta structure is still present in a leading spot section penumbra. The spot group
extends more than 30 degrees longitudinally. Further M class flaring is possible.
Region 13638 [S17E45] was mostly quiet and stable.
Region 13639 [N29E50] developed a magnetic delta structure in a
trailing penumbra. The region produced many C and M class flares.
Region 13641 [N11W00] was mostly quiet and stable.
New region 13642 [N17W10] emerged on April 14 and was numbered the
next day by SWPC.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9576 [N10W51] reemerged with a tiny spot.
S9588 [N18E14] was quiet and stable.
S9590 [S08W17] was quiet and stable.
New region S9594 [S23W63] emerged with tiny spots before noon,
then decayed slowly.
New region S9595 [S21W28] was observed with tiny spots in an old
plage area.
New region S9596 [S15E54] emerged with tiny spots.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C4.7 | 00:09 | 13639 | GOES16 | ||
| M1.7 | 01:18 | N28E63 (SDO/AIA) | 13639 | GOES16 | |
| C3.5 | 01:55 | 13639 | GOES16 | ||
| C2.9 | 02:18 | 13634 | GOES16 | ||
| C3.1 | 02:29 | 13639 | GOES16 | ||
| C4.5 | 03:09 | 13637 | GOES16 | ||
| C4.2 | 03:15 | 13639 | GOES16 | ||
| C6.3 | 03:33 | 13639 | GOES16 | simultaneous flare in AR 13634 | |
| C5.3 | 04:17 | 13639 | GOES16 | ||
| C5.5 | 04:46 | N28W30 | 13634 | GOES16 | |
| C4.1 | 05:01 | 13637 | GOES16 | simultaneous flare in AR 13639 | |
| C7.9 | 05:37 | N29W28 | 13634 | GOES16 | |
| C5.6 | 05:59 | 13637 | GOES16 | ||
| C3.8 | 06:22 | 13639 | GOES16 | ||
| C7.9 | 07:11 | 13639 | GOES16 | ||
| M1.0/1F | 07:32 | N30E57 | 13639 | GOES16 | |
| C5.1 | 08:25 | 13639 | GOES16 | ||
| M2.3/1B | 08:42 | N27W29 | 13634 | GOES16 | |
| C4.6 | 08:58 | 13639 | GOES16 | ||
| M1.2 | 09:32 | 13639 | GOES16 | ||
| C6.2 | 09:46 | 13639 | GOES16 | ||
| C2.2 | 10:34 | 13639 | GOES16 | ||
| C3.5 | 11:42 | 13639 | GOES16 | ||
| C2.0 | 13:22 | 13637 | GOES16 | ||
| M1.1/1F | 13:58 | N28E56 | 13639 | GOES16 | simultaneous flare in AR 13638 |
| M1.4 | 14:04 | N26W33 | 13634 | GOES16 | |
| M2.2 | 14:16 | 13639 | GOES16 | ||
| C2.5 | 16:42 | 13639 | GOES16 | ||
| C5.0 | 17:05 | 13639 | GOES16 | ||
| C2.5 | 17:54 | 13639 | GOES16 | ||
| C2.6 | 18:38 | 13639 | GOES16 | ||
| C4.2/1N | 19:12 | 13634 | GOES16 | ||
| M4.0/1N | 19:32 | 13639 | GOES16 | ||
| C2.9 | 20:08 | 13634 | GOES16 | ||
| C2.5 | 20:16 | 13642 | GOES16 | ||
| C2.1 | 20:31 | 13638 | GOES16 | ||
| C4.4 | 20:57 | N26E55 (SDO/AIA) | 13639 | GOES16 | |
| C5.2 | 21:43 | 13638 | GOES16 | ||
| C2.8 | 22:22 | 13634 | GOES16 | ||
| C3.9 | 23:55 | 13638 | GOES16 |
April 14: A faint CME was observed before noon, mainly off the
northeast limb. There's a chance this CME could have an Earth directed
component which could reach Earth on April 17.
April 13, 15: 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 recurrent negative polarity southern hemisphere coronal hole (CH1214) will likely rotate across the central meridian on April 17.
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 16 due to weak CME effects. Weak effects from another faint CME could reachg Earth on April 17 and cause some unsettled intervals that day and on April 18. Quiet conditions are likely on April 19. Quiet to active conditions will be possible on April 20-21 due to effects from CH1214.
| 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 | ||||||||||
| 13628 | 2024.04.02 2024.04.03 |
1 | N05W91 | 0060 | HSX |
 |
area: 0300 rotated out of view |
||||
| 13633 | 2024.04.05 2024.04.06 |
1 | 4 | 2 | S10W51 | 0080 | HSX | CSO |
 |
 |
area: 0160 location: S08W51 |
| 13634 | 2024.04.07 2024.04.08 |
23 | 18 | 9 | N25W42 | 0300 | EHI | DKO |
 |
 |
area: 0400 location: N27W42 |
| S9576 | 2024.04.08 | 1 | N10W51 | 0001 | AXX |
 |
|||||
| S9577 | 2024.04.08 | S18W45 | |||||||||
| 13635 | 2024.04.08 2024.04.10 |
3 | 13 | 5 | N22W14 | 0010 | BXO | CRO |
 |
 |
area: 0020 location: N20W15 |
| S9579 | 2024.04.09 | S15W40 | |||||||||
| S9580 | 2024.04.10 | N19W32 | |||||||||
| 13636 | 2024.04.10 2024.04.11 |
3 | 13 | 6 | S18E20 | 0090 | CSO | DAO |
 |
 |
location: S21E22 area: 0220 |
| 13637 | 2024.04.12 2024.04.13 |
2 | 34 | 16 | S12E39 | 0010 | BXO | FAI |
 |
 |
beta-gamma-delta location: S13E55 SWPC has split off the easternmost spot section into AR 13643 |
| 13638 | 2024.04.12 2024.04.13 |
4 | 13 | 9 | S17E44 | 0080 | CAO | DAO |
 |
 |
area: 0100 location: S17E45 |
| S9585 | 2024.04.12 | S25W34 | |||||||||
| 13639 | 2024.04.13 2024.04.14 |
14 | 26 | 16 | N30E48 | 0240 | EAI | DAI |
 |
 |
beta-delta location: N29E50 area: 0320 |
| 13641 | 2024.04.13 2024.04.14 |
19 | 11 | 7 | N11W01 | 0090 | DAO | DAO |
 |
 |
location: N11W00 area: 0210 |
| S9588 | 2024.04.13 | 8 | 2 | N18E14 | 0013 | BXO |
 |
 |
|||
| 13640 | 2024.04.14 | N21E44 | |||||||||
| S9590 | 2024.04.14 | 1 | 1 | S08W17 | 0005 | AXX |
 |
 |
|||
| 13642 | 2024.04.14 2024.04.15 |
5 | 10 | 7 | N18W11 | 0010 | BXO | CRO |
 |
 |
area: 0025 location: N17W10 |
| S9592 | 2024.04.14 | S04W14 |
 |
||||||||
| S9593 | 2024.04.14 | S20E11 |
 |
||||||||
| 13643 | 2024.04.15 | 8 | S10E63 | 0100 | DAI | currently part of AR 13637 | |||||
| S9594 | 2024.04.15 | 1 | S23W63 | 0001 | AXX |
 |
|||||
| S9595 | 2024.04.15 | 2 | S21W28 | 0003 | AXX |
 |
|||||
| S9596 | 2024.04.15 | 2 | S15W54 | 0003 | BXO |
 |
|||||
| Total spot count: | 83 | 157 | 80 | ||||||||
| Sunspot number: | 193 | 307 | 190 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 128 | 203 | 126 | (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): | 212 | 169 | 152 | ||||||||
| 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 | 135.6 (1) | 41.0 (2A) / 81.9 (2B) / 121.5 (2C) | (115.4 projected, -0.0) | (7.1) | |
| 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.
