The geomagnetic field was quiet on April 13. Solar wind speed at SOHO ranged between 361 and 424 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 159.5 - increasing 25.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.33). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 22000212 (planetary), 22101421 (Boulder), 33000345 (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 19 active regions using 2K resolution (SN: 466) and in 14 active regions using 1K resolution (SN: 280) SDO/HMI images.
Region 13272 [S20W16] decayed slowly and has
only one spot with mature penumbra left. and was
much less active than during the previous days. The region still has many small
spots and weak polarity
intermixing. There's a small chance of a minor M class flare. C1 flares:
C1.4 @ 02:50 UT
Region 13273 [N09W29] decayed slowly and quietly.
Region 13274 [S07W43] decayed slowly and quietly.
Region 13275 [N19E22] was quiet and stable.
Region 13276 [S22E34] was quiet and stable.
Region 13277 [N10W05] decayed slowly and quietly.
Region 13278 [N12W48] decayed slowly and quietly.
Region 13279 [S20E50] has M class flare potential and produced
several C flares during the day. C1 flares: C1.9 @ 17:38 UT
New region 13280 [S08W28] emerged on April 11 and was numbered by
SWPC 2 days later. The region has lots of small spots, polarity intermixing,
and a weak magnetic delta in a southern penumbra. M class flaring is
possible. C1 flares: C1.9 @ 05:40, C1.8 @ 23:44 UT
New region 13281 [S24E68] rotated into view on April 12 and was
numbered by SWPC the next day. C1 flares: C1.5 @ 03:35, C1.9 @ 12:47, C1.5 @
14:37 UT
Spotted regions not observed (or interpreted
differently) by SWPC:
S8429 [S24W58] reemerged with tiny spots.
S8445 [N26W06] was quiet and stable.
S8455 [N25E12] reemerged with tiny spots.
S8459 [N09E06] decayed slowly and quietly.
New region S8462 [N11E58] emerged before noon and developed quickly
after noon. C and minor M class flaring is possible. SWPC has assigned 13282
to this region.
New region S8463 [N17E68] emerged with tiny spots.
New region S8464 [S14E39] emerged with tiny spots.
New region S8465 [S23E82] rotated into view with a tiny spot.
C1 flares: C1.9 @ 16:02 UT
New region S8466 [S19E84] rotated into view with a tiny spot.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C4.0 | 00:53 | 13272 | GOES16 | ||
| C3.3 | 01:06 | S19E62 | 13279 | GOES16 | |
| C3.7 | 01:23 | S19E62 | 13279 | GOES16 | |
| C2.5 | 02:24 | S19E62 | 13279 | GOES16 | |
| C2.2 | 04:07 | 13280 | GOES16 | simultaneous flare in AR 13279 | |
| C2.0 | 04:34 | 13272 | GOES16 | simultaneous flare in AR 13281 | |
| C2.3 | 04:58 | 13279 | GOES18 | ||
| C2.2 | 06:07 | 13279 | GOES16 | ||
| C2.0 | 06:17 | 13279 | GOES16 | ||
| C3.9 | 07:59 | S20E56 | 13279 | GOES16 | |
| C3.8 | 08:20 | S23E75 | 13281 | GOES16 | |
| C2.0 | 10:00 | 13279 | GOES16 | ||
| C8.4 | 10:43 | S19W08 | 13272 | GOES16 | |
| C6.7 | 10:56 | S20E54 | 13279 | GOES16 | |
| C4.3 | 11:56 | S20E53 | 13279 | GOES16 | |
| C2.2 | 18:57 | 13281 | GOES16 | ||
| C2.1 | 20:36 | N10E68 | S8463 | GOES16 |
April 11-13: 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 couple of positive polarity coronal holes have recently rotated across the central meridian, they are both likely to be too far north and south to cause a geomagnetic disturbance.
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 conditions are likely on April 14-16.
| 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 | ||||||||||
| S8429 | 2023.04.04 | 4 | S24W58 | 0004 | BXO |
 |
|||||
| 13272 | 2023.04.05 2023.04.06 |
22 | 74 | 40 | S22W14 | 0150 | FAI | FAI |
 |
 |
beta-gamma location: S20W16 |
| S8434 | 2023.04.05 | S07W35 | |||||||||
| S8439 | 2023.04.07 | S29W45 |
 |
||||||||
| 13274 | 2023.04.08 2023.04.10 |
1 | S07W47 | 0002 | AXX |
 |
 |
location: S07W43 | |||
| 13278 | 2023.04.08 2023.04.12 |
1 | 5 | 1 | N12W46 | 0010 | AXX | BXO |
 |
 |
area: 0007 |
| 13273 | 2023.04.09 2023.04.09 |
3 | 12 | 3 | N09W29 | 0070 | CSO | CAO |
 |
 |
|
| 13275 | 2023.04.09 2023.04.10 |
1 | 5 | 2 | N19E22 | 0020 | HSX | HSX |
 |
 |
area: 0050 |
| S8445 | 2023.04.09 | 6 | 2 | N26W06 | 0008 | BXO |
 |
 |
|||
| S8446 | 2023.04.09 | N27W28 | |||||||||
| S8447 | 2023.04.09 | S09W19 | |||||||||
| 13276 | 2023.04.10 2023.04.10 |
1 | 2 | 1 | S22E34 | 0020 | HSX | HRX |
 |
 |
|
| 13277 | 2023.04.10 2023.04.11 |
3 | 2 | N10W05 | 0006 | BXO |
 |
 |
|||
| S8451 | 2023.04.10 | N29W54 | |||||||||
| 13279 | 2023.04.10 2023.04.12 |
15 | 50 | 27 | S20E51 | 0230 | DAI | EAI |
 |
 |
beta-gamma location: S20E50 |
| S8454 | 2023.04.10 | S01W48 | |||||||||
| S8455 | 2023.04.10 | 3 | N25E12 | 0006 | BXO |
 |
|||||
| S8456 | 2023.04.10 | S09W02 | |||||||||
| S8457 | 2023.04.10 | S33W37 | |||||||||
| S8459 | 2023.04.11 | 1 | 1 | N09E06 | 0003 | AXX |
 |
 |
|||
| 13280 | 2023.04.11 2023.04.13 |
8 | 71 | 40 | S09W27 | 0060 | DAO | DRI |
 |
 |
beta-gamma-delta location: S08W28
area: 0200 |
| 13281 | 2023.04.12 2023.04.13 |
3 | 19 | 10 | S23E71 | 0220 | DAO | EKO |
 |
 |
location: S24E68 area: 0470 |
| 13282 S8462 |
2023.04.13 2023.04.13 |
11 | 7 | N11E68 | 0120 | DAO |
 |
||||
| S8463 | 2023.04.13 | 2 | 1 | N17E68 | 0004 | AXX |
 |
||||
| S8464 | 2023.04.13 | 5 | 3 | S14E39 | 0012 | BXO |
 |
||||
| S8465 | 2023.04.13 | 1 | S23E82 | 0003 | AXX |
 |
|||||
| S8466 | 2023.04.13 | 1 | S19E84 | 0003 | AXX |
 |
|||||
| Total spot count: | 54 | 276 | 140 | ||||||||
| Sunspot number: | 134 | 466 | 280 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 89 | 317 | 181 | (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): | 147 | 256 | 224 | ||||||||
| 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 | 138.8 (1) | 28.1 (2A) / 64.8 (2B) / 127.1 (2C) | (126.4 projected, +5.4) | (8.6) | |
| 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.
