The geomagnetic field was quiet on April 20. Solar wind speed at SOHO ranged between 385 and 476 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.
Solar flux density measured at 20h UT on 2.8 GHz was 147.0 - decreasing 4.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.94. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.5). Three hour interval K indices: 21134211 (planetary), 31244322 (Boulder), 00011211 (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 12 active regions using 2K resolution (SN: 281) and in 11 active regions using 1K resolution (SN: 191) SDO/HMI images.
Region 13276 [S22W57] decayed slowly and quietly.
Region 13279 [S21W37] decayed slowly and
quietly.
Region 13281 [S22W22] decayed slowly and produced several C flares.
C1 flares: C1.8 @ 07:25 UT
Region 13282 [N11W31] gained spots in the leading and intermediate
spot sections. The region has polarity intermixing and an M class flare is
possible. C1 flares: C1.5 @ 06:41, C1.3 @ 11:47, C1.4 @ 13:12 UT
Region 13283 [S22W03] developed as new flux emerged gaining spots and
area. C1 flares: C1.8 @ 03:12, C1.4 @ 14:26, C1.4 @ 19:44, C1.2 @ 21:01 UT
Region 13284 [S09E28] decayed slowly and quietly.
Spotted regions not observed (or interpreted
differently) by SWPC:
S8473 [S31E18] was quiet and stable.
S8475 [N22E24] was quiet and stable.
New region S8478 [N12W66] emerged with a few spots.
New region S8479 [N06E37] emerged with tiny spots.
New region S8480 [S18E80] rotated into view and could produce C and M
class flares. C1 flares: C1.1 @ 02:18, C1.3 @ 04:47, C1.6 @ 15:21, C1.7 @
15:50, C1.3 @ 17:59, C1.2 @ 23:27 UT
New region S8481 [S12W00] was observed with tiny spots in an old
plage area.
AR 13272 behind the southwest limb produced a C1.6 flare at 08:53 UT
Minor update added at 20:55 UT on April 21: AR 13283 produced a long duration M1.6 flare peaking at 18:11 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 relatively fast asymmetrical full halo CME was observed beginning at 18:12 UT in LASCO C2 imagery. Earth could receive an impact on April 23, active to severe storm conditions are possible.
C2+ flares:
Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
C2.2 | 01:19 | behind NW limb | GOES16 | ||
C2.2 | 03:23 | 13281 | GOES16 | incorrectly attributed to AR 13284 by SWPC | |
C2.0 | 05:15 | behind SW limb | 13272 | GOES16 | |
C2.6 | 07:43 | 13281 | GOES16 | ||
C2.0 | 09:07 | 13281 | GOES16 | ||
C2.3 | 09:12 | 13281 | GOES16 | ||
C3.6 | 09:22 | 13281 | GOES16 | ||
C2.4 | 10:55 | 13281 | GOES16 | ||
C2.3 | 12:24 | S21E02 | 13283 | GOES16 | |
C3.3 | 16:23 | 13282 | GOES16 | simultaneous flare in AR S8480 | |
C2.3 | 22:30 | S24W19 | 13281 | GOES16 |
April 18-20: 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 trans equatorial coronal hole (CH1141) rotated across the central meridian on April 19 and closed. A large recurrent trans equatorial coronal hole 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 geomagnetic conditions are likely on April 21. Expect quiet to unsettled conditions on April 22-23 due to effects from CH1141, isolated active intervals are possible.
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 |
N18W72 |
location: N19W68 |
||||||||
13276 | 2023.04.10 2023.04.10 |
1 | 1 | S21W33 | 0010 | AXX | AXX |
real position: S22W57 area: 0001 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. It is unclear what the USAF observer is seeing and reporting. |
|||
13279 | 2023.04.10 2023.04.12 |
1 | 19 | 6 | S19W39 | 0010 | HAX | CRO |
location: S21W37 |
||
13281 | 2023.04.12 2023.04.13 |
6 | 29 | 15 | S22W22 | 0060 | BXO | CAI | |||
13282 | 2023.04.13 2023.04.13 |
23 | 55 | 30 | N12W28 | 0380 | FHI | FKI |
area: 0710 |
||
S8463 | 2023.04.13 | N20W21 | |||||||||
S8464 | 2023.04.13 | S13W54 | |||||||||
13283 | 2023.04.13 2023.04.16 |
4 | 32 | 19 | S20W01 | 0050 | BXO | DRI |
area: 0080 location: S22W03 |
||
S8466 | 2023.04.13 | S19W07 | |||||||||
S8467 | 2023.04.14 | N08W52 | |||||||||
S8468 | 2023.04.14 | N39W50 | |||||||||
13284 | 2023.04.17 2023.04.17 |
2 | 5 | 2 | S08E30 | 0010 | AXX | CRO |
location: S09E28 area: 0020 |
||
S8472 | 2023.04.17 | N20W49 | |||||||||
S8473 | 2023.04.19 | 5 | 2 | S31E18 | 0010 | BXO | |||||
S8474 | 2023.04.19 | N19E05 | |||||||||
S8475 | 2023.04.19 | 4 | 1 | N22E24 | 0008 | BXO | |||||
S8476 | 2023.04.19 | N16W53 | |||||||||
S8477 | 2023.04.19 | S22W23 | |||||||||
S8478 | 2023.04.20 | 4 | 2 | N12W66 | 0016 | DRO | |||||
S8479 | 2023.04.20 | 2 | 1 | N06E37 | 0004 | BXO | |||||
S8480 | 2023.04.20 | 2 | 2 | S18E80 | 0280 | HKX | |||||
S8481 | 2023.04.20 | 3 | 1 | S12W00 | 0007 | AXX | |||||
Total spot count: | 37 | 161 | 81 | ||||||||
Sunspot number: | 97 | 281 | 191 | (total spot count + 10 * number of spotted regions) | |||||||
Weighted SN: | 52 | 198 | 118 | (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): | 107 | 155 | 153 |
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 | 147.2 (1) | 60.4 (2A) / 90.7 (2B) / 144.1 (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.