The geomagnetic field was at quiet to active levels on April 18 due to effects from CH1285. The phi angle was in a negative sector nearly all day, consistent with what would be expected from this coronal hole. Solar wind speed at SOHO ranged between 401 and 537 km/sec, averaging 448 km/sec (-25 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at background levels.
Solar flux density measured at 20h UT on 2.8 GHz was 155.7 - decreasing 22.2 over the previous solar rotation. (Centered 365d average SF at 1 AU - 183 days ago: 195.16. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. SC25 smoothed 365d solar flux max: 195.86 on October 13, 2024 (subtracting a baseline solar flux level of 65, this is +62.6% compared to the SC24 peak and -1.7% compared to the SC23 peak). The Potsdam WDC planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 12.6). Three hour interval K indices: 34222233 (planetary), 34213312 (Boulder), 55323454 (Andenes).
The background x-ray flux is at the class C1 level (GOES 18).
At the time of counting spots (see image time), spots were observed in 13 active regions using 2K resolution (SN: 280) and in 9 active regions using 1K resolution (SN: 157) SDO/HMI images.
AR 14056 [S07W85] rotated mostly out of view.
AR 14060 [N08W40] decayed further and was
mostly quiet. C1 flares: C1.2 @ 14:16 UT
AR 14062 [S02E25] decayed slowly and was mostly quiet. C1 flares:
C1.8 @ 06:01 UT
AR 14063 [N07W17] decayed slowly and quietly.
AR 14064 [N11E48] gained a magnetic delta
configuration in a southern penumbra. A major flare is possible. C1 flares:
C1.3 @ 03:38, C1.2 @ 05:48, C1.6 @ 12:11, C1.4 @ 21:17 UT
AR 14065 [S30E50] gained a few spots and was quiet.
New AR 14067 [S02E58] emerged on April 17, developed slowly the next
day and was numbered by SWPC.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S10982 [S19W21] decayed slowly and quietly.
S10991 [N29W12] was quiet and stable.
S10992 [N15E07] was quiet and stable.
S10995 [N05E34] was quiet and stable.
New region S10996 [N32E04] emerged with tiny spots.
New region S10997 [S12W09] emerged with tiny spots.
AR 14061 produced a C1.5 flare at 07:16 UT while close to the northwest limb. An active region behind the southeast limb was the source of a C1.4 flare peaking at 17:59 UT.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.4 | 03:52 | 14062 | GOES19 | ||
| C2.2 | 04:22 | 14060 | GOES19 | ||
| C2.6 | 21:52 | 14064 | GOES19 | ||
| C2.3 | 23:21 | S27E90 (SDO/AIA) | GOES19 | ||
| M4.4 | 23:50 | S27E90 (SDO/AIA) | GOES19 | weak type II radio sweep |
April 16-18: No obviously Earth directed CMEs.
[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 negative polarity trans equatorial coronal hole (CH1285) was Earth facing on April 14. A positive polarity southern hemisphere coronal hole (CH1286) will rotate across the central meridian on April 18-21.
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 to fair.
The geomagnetic field is expected to be at quiet to unsettled levels on April 19 due to effects from CH1285. Effects associated with CH1286 could cause unsettled to minor storm levels on April 20-23.
| Coronal holes (1) | Coronal mass ejections (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 |
STAR | SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 14056 | 2025.04.05 2025.04.06 |
1 | 1 | S07W87 | 0030 | HRX | HRX |
 |
 |
was AR S10966 | |
| 14061 | 2025.04.06 2025.04.11 |
N18W87 |
 |
was AR S10969 location: N15W82 |
|||||||
| 14059 | 2025.04.09 2025.04.09 |
N13W71 |
was AR S10976 location: N14W64 |
||||||||
| 14060 | 2025.04.09 2025.04.10 |
5 | 18 | 9 | N08W42 | 0080 | CAO | CAO |
 |
 |
beta-gamma was AR S10977 area: 0100 location: N08W40 |
| S10980 | 2025.04.11 | S12W58 | |||||||||
| S10982 | 2025.04.13 | 8 | 1 | S19W21 | 0010 | BXO |
 |
 |
|||
| S10983 | 2025.04.14 | N22W57 | |||||||||
| 14062 | 2025.04.14 2025.04.15 |
13 | 50 | 28 | S03E24 | 0300 | DKI | FKO |
 |
 |
beta-gamma was AR S10984 area: 0760 location: S02E25 |
| S10985 | 2025.04.14 | N05E21 | |||||||||
| 14063 | 2025.04.15 2025.04.16 |
2 | N06W19 | 0003 | AXX |
 |
 |
was AR S10987 location: N07W17 |
|||
| 14064 | 2025.04.15 2025.04.16 |
9 | 28 | 13 | N11E45 | 0360 | DKI | EKC |
 |
 |
beta-delta was AR S10989 SWPC initially set the location of AR 14064 to S08E74, and then changed to the proper location the next day location: N11E48 area: 0780 |
| 14065 | 2025.04.16 2025.04.17 |
1 | 6 | 3 | S30E47 | 0030 | HSX | CAO |
 |
 |
was AR S10990 area: 0100 location: S30E50 |
| S10991 | 2025.04.16 | 2 | N29W12 | 0003 | BXO |
 |
 |
||||
| S10992 | 2025.04.16 | 9 | N15E07 | 0013 | BXO |
 |
 |
||||
| S10993 | 2025.04.16 | N21W41 | |||||||||
| 14066 | 2025.04.17 | 7 | S04E33 | 0030 | CAO | these are the trailing spots of AR 14062. There's no obvious reason for SWPC's split, which would make this an interpretational mistake | |||||
| 14067 | 2025.04.17 2025.04.18 |
7 | 15 | 8 | S02E55 | 0050 | CSO | DAO |
 |
 |
was AR S10994 location: S02E58 area: 0070 |
| S10995 | 2025.04.17 | 5 | 1 | N04E28 | 0010 | BXO |
 |
 |
|||
| S10996 | 2025.04.18 | 3 | 2 | N32E04 | 0010 | BXO |
 |
||||
| S10997 | 2025.04.18 | 3 | 2 | S12W09 | 0010 | BXO |
 |
||||
| Total spot count: | 43 | 150 | 67 | ||||||||
| Sunspot number: | 113 | 280 | 157 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 86 | 188 | 105 | (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): | 124 | 154 | 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 |
| 2023.10 | 142.8 | 141.9 | 99.9 | 124.8 (+0.8) | 8.16 |
| 2023.11 | 153.5 | 150.2 | 107.1 | 127.9 (+3.1) | 12.20 |
| 2023.12 | 151.1 | 146.4 | 113.5 | 129.5 (+1.6) | 9.60 |
| 2024.01 | 164.6 | 159.3 | 126.0 | 131.2 (+1.7) | 5.46 |
| 2024.02 | 172.5 | 168.3 | 123.0 | 136.9 (+5.7) | 5.31 |
| 2024.03 | 154.4 | 152.9 | 103.7 | 141.4 (+4.5) | 11.03 |
| 2024.04 | 161.3 | 162.6 | 137.0 | 144.5 (+3.1) | 9.69 |
| 2024.05 | 187.7 | 191.9 | 172.1 | 149.1 (+4.6) | 23.56 (SC25 peak) |
| 2024.06 | 184.3 | 190.2 | 164.1 | 152.7 (+3.6) | 10.24 |
| 2024.07 | 196.6 | 203.0 | 196.8 | 154.9 (+2.3) | 7.13 |
| 2024.08 | 246.1 (cycle peak) |
252.2 | 216.0 (SC25 peak) | 156.7 (+1.8) | 15.96 |
| 2024.09 | 195.7 | 197.8 | 141.1 | 159.3 (+1.6) | 15.36 |
| 2024.10 | 221.0 | 219.6 | 166.4 | (160.2 projected, +0.9) | 18.99 |
| 2024.11 | 199.6 | 195.3 | 152.5 | (157.6 projected, -2.6) | 9.33 |
| 2024.12 | 197.3 | 191.2 | 154.5 | (153.8 projected, -3.8) | 8.42 |
| 2025.01 | 190.3 | 184.2 | 137.0 | (148.3 projected, -5.5) | 13.17 |
| 2025.02 | 184.2 | 179.7 | 154.7 | (139.8 projected, -8.5) | 14.42 |
| 2025.03 | 163.7 | 162.1 | 134.2 | (133.4 projected, -6.4) | 15.96 |
| 2025.04 | 165.1 (1) | 72.0 (2A) / 120.0 (2B) / 136.5 (2C) | (128.8 projected, -4.6) | (22.3) | |
| 2025.05 | (123.5 projected, -5.3) | ||||
| 2025.06 | (118.6 projected, -4.9) | ||||
| 2025.07 | (114.5 projected, -4.1) | ||||
| 2025.08 | (109.8 projected, -4.7) | ||||
| 2025.09 | (105.5 projected, -4.3) | ||||
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 27 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: WDC-SILSO, Royal Observatory
Of Belgium, Brussels
Sunspot activity has been on a slowly decreasing trend since September 2024 (using the average solar flux over 3 solar rotations as a proxy). All 365 days smoothed sunspot numbers peaked on October 11-12, 2024, very likely making this the solar max. SDO1K 365d peak: 236.0, SDO2K 365d peak: 364.3, NOAA SN 365d peak: 156.0, ISN 365d peak: 163.5. The 365d smoothed solar flux peaked on October 13, 2024, only 1.7% below the SC23 peak, and 62.6% above the SC24 peak.
--------------------------------------------------------------------------------------
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.
