The geomagnetic field was quiet to unsettled on April 26 under the influence of effects from CH1142. Solar wind speed at SOHO ranged between 503 and 690 km/sec. The high latitude magnetometer at Andenes recorded unsettled to minor storm levels. What was likely the arrival of the April 24 CME was recorded at SOHO at 17:39 UT with a sudden increase in solar wind speed from 547 to 598 km/sec. Solar wind speed increased further to almost 700 km/sec later in the day.
Solar flux density measured at 20h UT on 2.8 GHz was 136.5 - decreasing 3.8 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.52. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 15 (STAR Ap - based on the mean of three hour interval ap indices: 14.8). Three hour interval K indices: 33233333 (planetary), 33223732 (Boulder), 45334355 (Andenes).
The background x-ray flux is at the class B7 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 15 active regions using 2K resolution (SN: 292) and in 11 active regions using 1K resolution (SN: 186) SDO/HMI images.
Region 13284 [S09W48] decayed slowly and quietly.
Region 13285 [S17E02] gained a number of small
spots and was quiet.
Region 13286 [S11E12] developed as new flux emerged in the trailing
spot section.
Region 13287 [S26E38] decayed slowly and quietly.
Region 13288 [S22E08] developed further and has
a small magnetic delta in the central spot section. M class flaring is
possible. C1 flares: C1.1 @ 03:55, C1.2 @ 08:13 UT
Region 13289 [N19E65] was mostly quiet and stable.
New region 13290 [N25W44] emerged on April 25 and was numbered by
SWPC the next day.
New region 13291 [N09E13] emerged on April 25 and received its NOAA
number the following day as more small spots formed.
Spotted regions not observed (or interpreted
differently) by SWPC:
S8486 [N27W16] was quiet and stable.
S8489 [N17W01] decayed slowly and quietly.
S8492 [N17W12] decayed slowly and quietly.
S8493 [S21W15] was quiet and stable.
S8497 [S17E32] decayed slowly and quietly.
S8498 [N15E70] was quiet and stable.
New region S8500 [N12E20] was observed with tiny spots in an old
plage area.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.5 | 14:23 | N22E68 | 13289 | GOES16 |
April 25-26: No obviously Earth directed CMEs were
observed.
April 24: A partial halo CME was observed after a filament eruption
in the southwest quadrant that began at 12:37 UT in SDO/AIA imagery. The CME
was likely the source of solar wind changes observed at SOHO at 17:39 UT on
April 26.
[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) was Earth facing on April 23-26. A northern hemisphere coronal hole (CH1143) will 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.
Quiet to active conditions are likely on April 27-29 due to combined effects from CH1142 and CME effects. On April 30-May 1 quiet to unsettled conditions are likely due to effects from CH1143.
| 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 | ||||||||||
| 13283 | 2023.04.13 2023.04.16 |
S23W84 |
location: S21W79 |
||||||||
| 13284 | 2023.04.17 2023.04.17 |
3 | S08W53 | 0003 | BXO |
 |
 |
location: S08W51 |
|||
| S8473 | 2023.04.19 | S33W51 |
 |
||||||||
| S8475 | 2023.04.19 | N26W46 | |||||||||
| S8479 | 2023.04.20 | N06W41 | |||||||||
| 13285 | 2023.04.20 2023.04.21 |
4 | 27 | 17 | S17E05 | 0120 | CSO | CAO |
 |
 |
location: S17E02 area: 0220 |
| S8482 | 2023.04.21 | S23W40 | |||||||||
| 13286 | 2023.04.21 2023.04.24 |
2 | 12 | 7 | S11E12 | 0010 | AXX | CRO |
 |
 |
area: 0030 |
| S8485 | 2023.04.22 | N16W24 | |||||||||
| S8486 | 2023.04.22 | 7 | 1 | N27W16 | 0012 | BXO |
 |
 |
|||
| 13287 | 2023.04.23 2023.04.24 |
2 | S25E35 | 0002 | BXO |
 |
 |
location: S26E38 | |||
| S8488 | 2023.04.23 | S26E04 | |||||||||
| S8489 | 2023.04.23 | 7 | 4 | N17W01 | 0013 | BXO |
 |
 |
|||
| 13288 | 2023.04.24 2023.04.25 |
5 | 39 | 23 | S22E10 | 0150 | DSO | EKI |
 |
 |
beta-delta area: 0340 location: S22E08 |
| S8492 | 2023.04.24 | 1 | 1 | N17W12 | 0002 | AXX |
 |
 |
|||
| S8493 | 2023.04.24 | 2 | S21W15 | 0004 | BXO |
 |
|||||
| 13289 | 2023.04.25 2023.04.25 |
3 | 5 | 3 | N20E58 | 0150 | DSO | DAC |
 |
 |
location: N19E65 area: 0250 SWPC location is way off |
| 13290 | 2023.04.25 2023.04.26 |
3 | 7 | 4 | N24W45 | 0040 | DRO | DRO |
 |
 |
|
| 13291 | 2023.04.25 2023.04.26 |
4 | 25 | 13 | N09E12 | 0020 | BXO | DRI |
 |
 |
area : 0080 |
| S8497 | 2023.04.25 | 2 | S17E32 | 0003 | BXO |
 |
 |
||||
| S8498 | 2023.04.25 | 1 | 1 | N15E70 | 0030 | HAX |
 |
 |
|||
| S8499 | 2023.04.25 | S27W11 |
 |
||||||||
| S8500 | 2023.04.26 | 2 | 2 | N12E20 | 0006 | AXX |
 |
||||
| Total spot count: | 21 | 142 | 76 | ||||||||
| Sunspot number: | 81 | 292 | 186 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 39 | 176 | 110 | (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): | 89 | 161 | 149 | ||||||||
| 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 | 144.7 (1) | 77.7 (2A) / 89.7 (2B) / 137.8 (2C) | (126.4 projected, +5.4) | (12.6) | |
| 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.
