The geomagnetic field was at quiet to unsettled levels on April 27, weakly under the influence of a high speed stream from CH1286/CH1288. Solar wind speed at SOHO ranged between 356 and 470 km/sec, averaging 420 km/sec (-39 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to active 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 16.2 over the previous solar rotation. The 365 days average solar flux at 1 AU was 194.32 (183 days ago). SC25 peak: 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 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.1). Three hour interval K indices: 12111322 (planetary), 23122421 (Boulder), 32212344 (Andenes).
The background x-ray flux is at the class C1 level (GOES 19).
At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 279) and in 12 active regions using 1K resolution (SN: 161) SDO/HMI images.
AR 14064 [N10W73] decayed slowly and produced a
few low level C flares.
AR 14065 [S31W64] was quiet and stable.
AR 14068 [S25W14] was quiet and stable.
AR 14069 [S08W62] was quiet and stable.
AR 14070 [S12W29] gained spots after noon and has minor polarity
intermixing. C1 flares: C1.1 @ 00:53, C1.4 @ 17:24 UT
AR 14072 [S18E09] was mostly quiet and stable.
AR 14073 [N12W02] decayed slowly and quietly.
AR 14075 [S09E18] decayed slowly and quietly.
AR 14076 [N06E31] was quiet and stable.
AR 14077 [S16E33] decayed slowly and quietly.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S10999 [N16W28] was mostly quiet and stable. C1 flares: C1.2 @ 13:45
UT
S11009 [S08W11] reemerged with a tiny spot.
S11010 [N24W51] was quiet and stable.
S11021 [N18E40] reemerged with tiny spots.
S11022 [N20W01] was quiet and stable.
S11027 [S14E49] was quiet and stable.
A C1.3 flare at 08:28 UT appears to have its origin behind the NE limb, the same applies to a C1.4 flare at 18:24 and a C1.5 flare at 20:42 UT.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.1 | 18:48 | N08W72 | 14064 | GOES19 | |
| C2.1 | 22:44 | 14064 | GOES19 |
April 25-27: 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 very large positive polarity southern hemisphere coronal hole (CH1286) rotated across the central meridian on April 17-25. A northern hemisphere positive polarity coronal hole (CH1288) was Earth facing on April 24. A northern hemisphere negative polarity coronal hole (CH1289) will likely rotate across the central meridian on April 28-29.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be at quiet to unsettled levels on April 28-29 due to effects from CH1286/CH1288. Quiet levels are likely on April 30 and May 1.
| 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 | ||||||||||
| 14064 | 2025.04.15 2025.04.16 |
4 | 7 | 4 | N12W72 | 0100 | DSO | DAO |
 |
 |
was AR S10989 location: N10W73 area: 0220 |
| 14065 | 2025.04.16 2025.04.17 |
1 | 3 | 1 | S31W65 | 0030 | HSX | HSX |
 |
 |
was AR S10990 location: S31W64 area: 0060 |
| 14067 | 2025.04.17 2025.04.18 |
S04W68 |
was AR S10994 location: S03W65 |
||||||||
| S10999 | 2025.04.19 | 20 | 2 | N16W28 | 0030 | BXO |
 |
 |
|||
| 14074 | 2025.04.19 2025.04.25 |
S20W87 |
 |
was AR S11000 location: S19W85 |
|||||||
| 14068 | 2025.04.20 2025.04.21 |
1 | 10 | 4 | S25W17 | 0010 | HRX | CRO |
 |
 |
was AR S11002 location: S24W14 area: 0020 |
| 14070 | 2025.04.20 2025.04.22 |
11 | 29 | 13 | S12W28 | 0110 | DSO | EAI |
 |
 |
beta-gamma was AR S11004 area: 0220 location: S12W29 |
| 14069 | 2025.04.20 2025.04.22 |
1 | 3 | 1 | S09W59 | 0010 | AXX | CRO |
 |
 |
was AR S11006 location: S08W62 |
| S11007 | 2025.04.21 | N10W52 | |||||||||
| S11009 | 2025.04.21 | 1 | S08W11 | 0002 | AXX |
 |
|||||
| S11010 | 2025.04.22 | 1 | N24W51 | 0001 | AXX |
 |
 |
||||
| 14072 | 2025.04.22 2025.04.23 |
4 | 11 | 6 | S19E11 | 0050 | HSX | CAO |
 |
 |
was AR S11011 area: 0130 location: S18E09 |
| S11012 | 2025.04.22 | S14W41 | |||||||||
| 14073 | 2025.04.23 2025.04.24 |
2 | 6 | 3 | N11W00 | 0010 | BXO | BXO |
 |
 |
was AR S11015 location: N12E12 area: 0015 |
| 14076 | 2025.04.23 2025.04.25 |
1 | 4 | 1 | N05E30 | 0080 | HSX | HSX |
 |
 |
was AR S11017 area: 0180 location: N06E31 |
| 14075 | 2025.04.23 2025.04.25 |
3 | S11E20 | 0005 | BXO |
 |
 |
was AR S11018 location: S09E18 |
|||
| 14077 | 2025.04.24 2025.04.25 |
4 | 10 | 3 | S16E32 | 0020 | HRX | CRO |
 |
 |
was AR S11020 area: 0030 location: S16E33 |
| S11021 | 2025.04.24 | 2 | 1 | N18E40 | 0005 | BXO |
 |
||||
| S11022 | 2025.04.24 | 6 | 2 | N20W01 | 0010 | BXO |
 |
 |
|||
| S11025 | 2025.04.25 | S10E09 |
 |
||||||||
| S11026 | 2025.04.26 | S23W02 |
 |
||||||||
| S11027 | 2025.04.26 | 3 | S14E47 | 0005 | AXX |
 |
 |
||||
| Total spot count: | 29 | 119 | 41 | ||||||||
| Sunspot number: | 119 | 279 | 161 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 60 | 143 | 75 | (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): | 131 | 153 | 129 | ||||||||
| 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 | 152.8 (+3.7) | 10.24 |
| 2024.07 | 196.6 | 203.0 | 196.8 | 155.0 (+2.3) | 7.13 |
| 2024.08 | 246.1 (cycle peak) |
252.2 | 216.0 (SC25 peak) | 156.8 (+1.8) | 15.96 |
| 2024.09 | 195.7 | 197.8 | 141.1 | 159.4 (+1.6) | 15.36 |
| 2024.10 | 221.0 | 219.6 | 165.8 | (160.3 projected, +0.9) | 18.99 |
| 2024.11 | 199.6 | 195.3 | 154.1 | (157.7 projected, -2.6) | 9.33 |
| 2024.12 | 197.3 | 191.2 | 154.6 | (153.9 projected, -3.8) | 8.42 |
| 2025.01 | 190.3 | 184.2 | 137.0 | (148.4 projected, -5.5) | 13.17 |
| 2025.02 | 184.2 | 179.7 | 154.7 | (139.9 projected, -8.5) | 14.42 |
| 2025.03 | 163.7 | 162.1 | 134.2 | (133.5 projected, -6.4) | 15.96 |
| 2025.04 | 163.9 (1) | 113.5 (2A) / 126.1 (2B) / 148.8 (2C) ISN average: 140 |
(128.9 projected, -4.6) | (19.2) | |
| 2025.05 | (123.6 projected, -5.3) | ||||
| 2025.06 | (118.6 projected, -5.0) | ||||
| 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: 236.1, SDO2K 365d peak: 364.4, NOAA SN 365d peak: 156.0, ISN 365d peak: 163.6. 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 whichever 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.
