The geomagnetic field was quiet to very severe storm on April 23. Solar wind speed at SOHO ranged between 356 and 754 km/sec. The high latitude magnetometer at Andenes recorded quiet to severe storm levels. A strong solar wind shock was observed at SOHO at 17:03 UT with an abrupt increase in solar wind speed from 389 to 539 km/sec. The Bz component of the interplanetary magnetic field was strongly southwards for the first 3 hours after the impact, then mostly northwards until 00:45 UT on April 24. The main body of the disturbance arrived at DSCOVR near 01:10 UT with Bz peaking at -33 nT.
Solar flux density measured at 20h UT on 2.8 GHz was 135.2 - decreasing 23.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.69. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 64 (STAR Ap - based on the mean of three hour interval ap indices: 64.4). Three hour interval K indices: 22235687 (planetary), 22244455 (Boulder), 54145675 (Andenes).
The background x-ray flux is at the class B5 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 238) and in 12 active regions using 1K resolution (SN: 153) SDO/HMI images.
Region 13279 [S18W78] decayed slowly and was
mostly quiet. C1 flares: C1.1 @ 02:47 UT
Region 13281 [S24W57] decayed slowly and quietly.
Region 13282 [N12W74] was mostly quiet and
stable. C1 flares: C1.1 @ 17:11, C1.0 @ 20:38 UT
Region 13283 [S21W43] decayed slowly and quietly.
Region 13284 [S08W12] was quiet and stable.
Region 13285 [S17E43] was quiet and stable.
Spotted regions not observed (or interpreted
differently) by SWPC:
S8473 [S33W21] was quiet and stable.
S8475 [N27W18] was quiet and stable.
S8482 [S23W01] decayed slowly and quietly.
S8483 [S10E54] decayed slowly and quietly.
S8485 [N16E15] was quiet and stable.
S8486 [N27E15] was quiet and stable.
S8487 [S24E74] rotated into view with a small spot.
New region S8488 [S26E43] emerged with a tiny spot.
New region S8489 [N17E37] emerged with tiny
spots.
New region S8490 [N36W43] emerged with a tiny spot at a high
latitude.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.2 | 06:40 | 13279 | GOES16 |
April 22-23: No obviously Earth directed CMEs were
observed.
April 21: AR 13283 produced a long duration M1.6 flare peaking at
18:12 UT. The flare involved filaments to the east and west of the region
across the central meridian. An EIT wave was observed over large parts of
both the southern and northern hemisphere. A full halo CME was observed
beginning at 18:12 UT in LASCO C2 imagery. The CME reached Earth on April
23.
[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 trans equatorial coronal hole (CH1142) will be Earth facing on April 23-26.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is very poor. Propagation on long distance northeast-southwest paths is poor.
Active to very severe storm conditions are likely on April 24 becoming quiet to minor storm on April 25. Quiet to minor storm conditions are expected for April 26-28 due to effects from CH1142.
| Coronal holes (1) | Coronal mass ejection (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 | ||||||||||
| 13279 | 2023.04.10 2023.04.12 |
3 | 3 | 2 | S19W78 | 0020 | CRO | CRO |
 |
 |
location: S18W78 area: 0010 |
| 13281 | 2023.04.12 2023.04.13 |
2 | 2 | S24W58 | 0010 | AXX | AXX |
 |
 |
area: 0002 location: S24W57 |
|
| 13282 | 2023.04.13 2023.04.13 |
8 | 13 | 8 | N12W70 | 0300 | FKI | FKO |
 |
 |
area: 0510 location: N12W74 |
| 13283 | 2023.04.13 2023.04.16 |
4 | 9 | 2 | S22W41 | 0010 | BXO | CRO |
 |
 |
area: 0014 location: S21W43 |
| S8466 | 2023.04.13 | S19W46 | |||||||||
| 13284 | 2023.04.17 2023.04.17 |
2 | 7 | 4 | S08W13 | 0010 | AXX | CRO |
 |
 |
location: S08W12 area: 0015 |
| S8473 | 2023.04.19 | 4 | 1 | S33W21 | 0007 | BXO |
 |
 |
|||
| S8474 | 2023.04.19 | N20W34 |
 |
||||||||
| S8475 | 2023.04.19 | 6 | 1 | N27W18 | 0010 | BXO |
 |
 |
|||
| S8479 | 2023.04.20 | N06W02 | |||||||||
| 13285 | 2023.04.20 2023.04.21 |
7 | 19 | 10 | S17E44 | 0190 | DAO | EKO |
 |
 |
area: 0430 |
| S8481 | 2023.04.20 | S12W39 | |||||||||
| S8482 | 2023.04.21 | 1 | S23W01 | 0001 | AXX |
 |
 |
||||
| S8483 | 2023.04.21 | 2 | 1 | S10E54 | 0008 | AXX |
 |
 |
|||
| S8485 | 2023.04.22 | 3 | N16E15 | 0004 | BXO |
 |
 |
||||
| S8486 | 2023.04.22 | 3 | 1 | N27E15 | 0005 | AXX |
 |
 |
|||
| S8487 | 2023.04.23 | 2 | 1 | S24E74 | 0010 | HRX |
 |
||||
| S8488 | 2023.04.23 | 1 | S26E43 | 0002 | AXX |
 |
|||||
| S8489 | 2023.04.23 | 2 | 1 | N17E37 | 0005 | AXX |
 |
||||
| S8490 | 2023.04.23 | 1 | 1 | N36W43 | 0003 | AXX |
 |
||||
| Total spot count: | 26 | 78 | 33 | ||||||||
| Sunspot number: | 86 | 238 | 153 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 42 | 110 | 65 | (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): | 95 | 131 | 122 | ||||||||
| 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 |
| 2021.09 | 87.0 | 88.2 | 51.3 | 40.2 (+4.8) | 6.33 |
| 2021.10 | 88.9 | 88.3 | 37.4 | 45.2 (+5.0) | 7.38 |
| 2021.11 | 86.2 | 84.4 | 34.8 | 50.8 (+5.6) | 9.83 |
| 2021.12 | 103.0 | 99.8 | 67.5 | 55.9 (+5.1) | 6.40 |
| 2022.01 | 103.8 | 100.5 | 55.3 | 60.1 (+4.2) | 8.92 |
| 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 | 92.5 (+5.8) | 10.92 |
| 2022.09 | 135.1 | 136.5 | 96.0 | 96.4 (+3.9) | 12.18 |
| 2022.10 | 133.5 | 132.7 | 95.5 | (99.0 projected, +2.6) | 11.16 |
| 2022.11 | 123.4 | 120.7 | 80.5 | (102.0 projected, +3.0) | 9.33 |
| 2022.12 | 147.9 | 143.4 | 112.8 | (106.8 projected, +4.8) | 10.99 |
| 2023.01 | 182.4 | 176.6 | 143.6 | (112.9 projected, +6.1) | 8.73 |
| 2023.02 | 167.2 | 163.2 | 110.9 | (117.9 projected, +5.0) | 14.48 (current SC25 peak) |
| 2023.03 | 157.2 | 155.6 | 122.6 | (121.0 projected, +3.1) | 14.42 |
| 2023.04 | 146.1 (1) | 70.0 (2A) / 91.3 (2B) / 140.6 (2C) | (126.4 projected, +5.4) | (10.4) | |
| 2023.05 | (132.1 projected, +5.7) | ||||
| 2023.06 | (135.2 projected, +3.1) | ||||
| 2023.07 | (134.7 projected, -0.5) | ||||
| 2023.08 | (135.7 projected, +1.0) | ||||
| 2023.09 | (139.2 projected, +3.5) | ||||
| 2023.11 | (142.5 projected max SC25) | ||||
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: SIDC-SILSO.
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.
