The geomagnetic field was quiet to unsettled on April 21, likely under the influence of effects from CH1141 after noon. Solar wind speed at SOHO ranged between 356 and 411 km/sec. The high latitude magnetometer at Andenes recorded quiet to major storm levels.
Solar flux density measured at 17h UT on 2.8 GHz was 140.7 - decreasing 19.6 over the previous solar rotation. The value recorded at 20h UT was enhanced due to the M1 flare and therefore discarded. (Centered 1 year average SF at 1 AU - 183 days ago: 139.81. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.9). Three hour interval K indices: 21122223 (planetary), 22223422 (Boulder), 11023366 (Andenes).
The background x-ray flux is at the class B9 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 13 active regions using 2K resolution (SN: 260) and in 10 active regions using 1K resolution (SN: 158) SDO/HMI images.
Region 13279 [S18W50] saw new flux emerged in
the northern part of the trailing polarity area. Many tiny spots developed.
Region 13281 [S22W36] decayed slowly and quietly.
Region 13282 [N11W46] developed a small magnetic delta to the
southeast of the main penumbra. An M class flare is
possible. C1 flares: C1.2 @ 00:22 UT
Region 13283 [S22W14] decayed slowly and the M flare in the afternoon
was somewhat surprising.
Region 13284 [S09E15] decayed slowly and quietly.
New region 13285 [S18E70] rotated partly into view on April 20 and
was numbered the next day by SWPC. C1 flares: C1.1 @ 02:14, C1.2 @ 23:41 UT
Spotted regions not observed (or interpreted
differently) by SWPC:
S8473 [S33E09] was quiet and stable.
S8474 [N17W09] reemerged with tiny spots.
S8475 [N23E18] was quiet and stable.
S8478 [N12W80]decayed slowly and quietly.
New region S8482 [S24E26] emerged with tiny
spots.
New region S8483 [S11E81] rotated into view with tiny spots.
New region S8484 [N00W59] emerged with a tiny spot.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| M1.7/2N | 18:12 | S22W11 | 13283 | GOES16 | strong type II and moderate type IV radio sweeps full halo CME |
| C4.4 | 19:36 | 13285 | GOES16 | ||
| C2.1 | 21:00 | 13282 | GOES16 | ||
| C4.0 | 22:23 | S18W49 | 13279 | GOES16 |
April 19-20: 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. Earth could receive an impact on
April 23 or 24, active to severe storm conditions are possible.
[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 trans equatorial coronal hole (CH1141) rotated across the central meridian on April 19 and closed. A large recurrent trans equatorial coronal hole (CH1142) will likely become Earth facing on April 23-25.
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.
Quiet to unsettled geomagnetic conditions are likely on April 22-23 due to effects from CH1141, isolated active intervals are possible. Active to severe storm conditions are likely when the April 21 CME impacts Earth on April 23-24 with disturbed conditions likely lasting until April 25-26.
| 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 | ||||||||||
| 13275 | 2023.04.09 2023.04.10 |
2 | N13W85 | 0010 | BXO |
location: N19W81 SWPC position is way off |
|||||
| 13276 | 2023.04.10 2023.04.10 |
S21W47 |
 |
real position: S22W70 SWPC inexplicably moved this region 43 degrees eastwards on April 19 to the position of the trailing spots of AR 13281. On April 20 the region was repositioned once again, now 33 degrees longitude westwards and close to AR 13279. It is unclear what the USAF observer was seeing and reporting. |
|||||||
| 13279 | 2023.04.10 2023.04.12 |
1 | 17 | 5 | S22W50 | 0010 | AXX | CRI |
 |
 |
location: S18W50 area: 0030 |
| 13281 | 2023.04.12 2023.04.13 |
7 | 14 | 7 | S21W35 | 0030 | CRO | CRO |
 |
 |
area: 0040 location: S22W36 |
| 13282 | 2023.04.13 2023.04.13 |
19 | 40 | 20 | N11W42 | 0410 | FKI | FKI |
 |
 |
beta-delta area: 0650 |
| S8463 | 2023.04.13 | N20W34 | |||||||||
| 13283 | 2023.04.13 2023.04.16 |
10 | 22 | 14 | S22W14 | 0020 | CRO | DRI |
 |
 |
area: 0040 location: S22W15 |
| S8466 | 2023.04.13 | S19W20 | |||||||||
| 13284 | 2023.04.17 2023.04.17 |
1 | 5 | 2 | S00E14 | 0010 | HRX | CRO |
 |
 |
location: S09E15 area: 0020 SWPC location is way off |
| S8473 | 2023.04.19 | 5 | 2 | S33E09 | 0012 | BXO |
 |
 |
|||
| S8474 | 2023.04.19 | 5 | 1 | N17W09 | 0010 | BXO |
 |
||||
| S8475 | 2023.04.19 | 9 | N23E18 | 0013 | BXO |
 |
 |
||||
| S8477 | 2023.04.19 | S22W36 | |||||||||
| S8478 | 2023.04.20 | 2 | N12W80 | 0004 | BXO |
 |
 |
||||
| S8479 | 2023.04.20 | N06E24 |
 |
||||||||
| 13285 | 2023.04.20 2023.04.21 |
4 | 6 | 4 | S17E69 | 0140 | DSO | EHO |
 |
 |
area: 0470 |
| S8481 | 2023.04.20 | S12W13 |
 |
||||||||
| S8482 | 2023.04.21 | 2 | 2 | S24E26 | 0005 | BXO |
 |
||||
| S8483 | 2023.04.21 | 2 | 1 | S11E81 | 0004 | AXX |
 |
||||
| S8484 | 2023.04.21 | 1 | N00W59 | 0001 | AXX |
 |
|||||
| Total spot count: | 44 | 130 | 58 | ||||||||
| Sunspot number: | 114 | 260 | 158 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 68 | 162 | 90 | (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): | 125 | 143 | 126 | ||||||||
| 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 | 146.8 (1) | 64.2 (2A) / 91.8 (2B) / 144.3 (2C) | (126.4 projected, +5.4) | (8.1) | |
| 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.
