The geomagnetic field was quiet on April 13. 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.
Solar flux density measured at 20h UT on 2.8 GHz was 161.0 - increasing 9.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.80. 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 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 12101112 (planetary), 22113311 (Boulder), 22012103 (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 13 active regions using 2K resolution (SN: 243) and in 9 active regions using 1K resolution (SN: 146) SDO/HMI images.
Region 13628 [N07W63] was quiet and stable.
Region 13633 [S08W24] decayed slowly and quietly.
Region 13634 [N26W17] gained area and has become a compact spot
group. A minor M class flare is possible. C1 flares: C1.8 @ 08:31 UT
Region 13635 [N20E12] decayed slowly and quietly.
Region 13636 [S20E48] was mostly quiet and stable.
New region 13637 [S12E69] rotated partly into view on April 12 and
was numbered by SWPC the next day. Small trailing spots rotated into view on
April 13. The region has a magnetic delta structure in a small leading
penumbra, and this delta was the source of an impulsive M4.3 @ 02:33 UT on
April 14. C1 flares: C1.8 @ 18:42 UT
New region 13638 [S17E71] rotated into view on April 12 and was
number the following day by SWPC.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9570 [S15W52] was quiet and stable.
S9576 [N08W14] was quiet and stable.
S9577 [S18W19] was quiet and stable.
New region S9586 [N28E75] rotated into view with a few spots. C1
flares: C1.9 @ 00:55, C1.8 @ 11:55, C1.9 @ 13:36, C1.8 @ 17:21, C1.6 @ 19:47
UT
New region S9587 [N11E27] emerged with small and tiny spots.
New region S9588 [N14E38] was observed with tiny spots in an
old plage area.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| M2.4 | 05:02 | S12E80 (SDO/AIA) | 13637 | GOES16 | |
| C2.3 | 07:37 | N28E90 | S9586 | GOES16 | |
| C2.6 | 09:23 | S12E90 (SDO/AIA) | 13637 | GOES16 | |
| C2.7 | 09:36 | S13E75 (SDO/AIA) | 13637 | GOES16 | |
| C2.1 | 10:36 | S13E75 (SDO/AIA) | 13637 | GOES16 | |
| C2.1 | 12:21 | S13E74 (SDO/AIA) | 13637 | GOES16 | |
| C2.4 | 12:44 | N28E90 (SDO/AIA) | S9586 | GOES16 | |
| C2.0 | 13:22 | N28E90 (SDO/AIA) | S9586 | GOES16 | |
| C3.3 | 14:04 | S10E90 (SDO/AIA) | 13637 | GOES16 | |
| C5.5 | 15:00 | N28W09 (SDO/AIA) | 13634 | GOES16 | |
| C2.0 | 16:01 | 13635 | GOES16 | ||
| C2.1 | 21:09 | S18E76 (SDO/AIA) | 13638 | GOES16 |
April 11: A CME was observed after a filament eruption in the
northeast quadrant near the central meridian. The eruption began at 05:27 UT
in SDO/AIA imagery and peaked near 06h UT. The CME could reach Earth on
April 14.
April 12: A faint CME was observed after a filament eruption in the
southwest quadrant early in the day. The CME could reach Earth early on
April 15.
April 13: 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 southern hemisphere coronal hole (CH1213) rotated across the central meridian on April 9-10.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to active on April 14-15 due to weak CME effects from the CMEs observed on April 11 and 12. Quiet conditions are likely on April 16-17.
| 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 |
4 | 6 | 3 | N07W64 | 0180 | HAX | CKO |
 |
 |
area: 0370 location: N07W63 |
| 13632 | 2024.04.03 2024.04.05 |
N26W65 | location: N26W58 | ||||||||
| 13633 | 2024.04.05 2024.04.06 |
8 | 7 | 5 | S08W23 | 0110 | CSO | CSO |
 |
 |
location: S08W24 area: 0190 |
| S9570 | 2024.04.05 | 4 | S15W52 | 0005 | BXO |
 |
 |
||||
| 13634 | 2024.04.07 2024.04.08 |
17 | 35 | 21 | N27W17 | 0280 | DKI | DAC |
 |
 |
area: 0450 location: N26W17 |
| S9575 | 2024.04.07 | S03W48 | |||||||||
| S9576 | 2024.04.08 | 3 | N08W19 | 0006 | BXO |
 |
 |
||||
| S9577 | 2024.04.08 | 4 | S18W19 | 0008 | BXO |
 |
 |
||||
| 13635 | 2024.04.08 2024.04.10 |
7 | 22 | 10 | N23E13 | 0030 | CAO | CAO |
 |
 |
area: 0040 location: N20E12 |
| S9579 | 2024.04.09 | S15W14 | |||||||||
| S9580 | 2024.04.10 | N19W06 | |||||||||
| 13636 | 2024.04.10 2024.04.11 |
5 | 6 | 3 | S21E46 | 0100 | CSO | CSO |
 |
 |
location: S20E48 area: 0170 |
| 13637 | 2024.04.12 2024.04.13 |
3 | 8 | 6 | S11E66 | 0020 | CRO | FRO |
 |
beta-delta area: 0070 location: S12E69 |
|
| 13638 | 2024.04.12 2024.04.13 |
1 | 2 | 1 | S17E70 | 0030 | HSX | HSX |
 |
 |
area: 0080 location: S17E71 |
| S9585 | 2024.04.12 | S25W08 |
 |
||||||||
| S9586 | 2024.04.13 | 4 | 2 | N28E75 | 0080 | DAO |
 |
||||
| S9587 | 2024.04.13 | 8 | 5 | N11E27 | 0030 | DRI |
 |
||||
| S9588 | 2024.04.13 | 4 | N14E38 | 0004 | AXX |
 |
|||||
| Total spot count: | 45 | 113 | 56 | ||||||||
| Sunspot number: | 115 | 243 | 146 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 83 | 159 | 102 | (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): | 127 | 134 | 117 | ||||||||
| 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 | 128.0 (1) | 29.5 (2A) / 68.0 (2B) / 118.3 (2C) | (115.4 projected, -0.0) | (7.4) | |
| 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.
