The geomagnetic field was at unsettled to minor storm levels on April 6 due to effects associated with CH1281. Solar wind speed at SOHO ranged between 544 and 741 km/sec, averaging 654 km/sec (-37 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded unsettled to major storm levels. The above 10 MeV proton flux was at background levels most of the day, however a minor increase was observed after noon with a peak of 0.9 pfu at 20:50 UT.
Solar flux density measured at 20h UT on 2.8 GHz was 167.0 - increasing 17.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 195.37. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. Current SC25 peak: 195.37 on October 6, 2024 (subtracting a baseline solar flux level of 65, this is +61.95% compared to the SC24 peak and -2.09% compared to the SC23 peak). The Potsdam WDC planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 20.1). Three hour interval K indices: 53343333 (planetary), 43343332 (Boulder), 65334455 (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 14 active regions using 2K resolution (SN: 308) and in 11 active regions using 1K resolution (SN: 179) SDO/HMI images.
AR 14045 [S13W58] was mostly quiet and stable.
C1 flares: C1.6 @ 12:47 UT
AR 14046 [N06W49] was quiet and stable.
AR 14048 [S16W24] decayed slowly and produced a few C flares. C1
flares: C1.6 @ 03:34, C1.9 @ 10:41, C1.6 @ 11:57 UT
AR 14049 [S31W49] decayed slowly and quietly.
AR 14050 [N28W53] decayed slowly and quietly.
AR 14052 [S21W61] decayed slowly and quietly.
AR 14053 [S08W47] decayed slowly and quietly.
AR 14054 [S12W02] developed further and was
mostly quiet. C1 flares: C1.7 @ 07:18, C1.9 @ 22:27 UT
AR 14055 [N08E22] was mostly quiet and stable.
New AR 14056 [S06E72] rotated into view on April 5 and was numbered
the next day by SWPC.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S10964 [N08E69] was quiet and stable.
New region S10967 [N11W13] emerged with tiny spots.
New region S10968 [N20E36] emerged with a tiny spot.
New region S10969 [N13E73] rotated into view with a small spot.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.1 | 05:15 | behind NW limb | 14043 | GOES18 | |
| C2.4 | 05:33 | behind NW limb | 14043 | GOES18 | |
| C2.5 | 05:52 | behind NW limb | 14043 | GOES18 | |
| C2.9 | 15:53 | behind NW limb | 14043 | GOES16 | |
| C2.7 | 15:57 | 14045 | GOES16 | ||
| C2.0 | 17:44 | S13W55 | 14045 | GOES16 | |
| C2.3 | 19:57 | S17W23 | 14048 | GOES16 | |
| C2.0 | 22:02 | 14048 | GOES16 |
April 4-6: 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 small negative polarity northern hemisphere coronal hole (CH1282) was Earth facing on April 4. A small negative polarity trans equatorial coronal hole (CH1283) rotated across the central meridian on April 5-6. A negative polarity southern hemisphere coronal hole (CH1284) will become Earth facing on April 7-8.
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 active levels on April 7-8 due to effects associated first with CH1281 and then with CH1282. Effects from CH1283 could prolong the disturbance into April 9-10 quiet to minor storm levels.
| 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 | ||||||||||
| 14044 | 2025.03.26 2025.03.27 |
3 | N21W82 | 0110 | DAO |
 |
was AR S10929 location: N20W86 rotated out of view |
||||
| 14045 | 2025.03.27 2025.03.27 |
2 | 8 | 2 | S13W60 | 0010 | BXO | CRO |
 |
 |
was AR S10932 location: S13W58 area: 0020 |
| 14046 | 2025.03.27 2025.03.28 |
1 | 1 | 1 | N06W49 | 0200 | HSX | HHX |
 |
 |
was AR S10935 area: 0330 |
| 14048 | 2025.03.28 2025.03.29 |
22 | 82 | 35 | S16W28 | 0480 | FKC | FAI |
 |
 |
beta-gamma was AR S10940 location: S16W24 area: 0800 |
| 14050 | 2025.03.29 2025.04.02 |
4 | 9 | 3 | N27W52 | 0030 | CAO | BXO |
 |
 |
was AR S10942 area: 0020 location: N28W53 |
| 14049 | 2025.03.29 2025.03.31 |
6 | 7 | 4 | S30W55 | 0070 | DAO | EAO |
 |
 |
was AR S10943 area: 0120 location: S31W49 SWPC location is way off |
| S10948 | 2025.03.30 | N21W52 | |||||||||
| S10952 | 2025.04.01 | S22W43 | |||||||||
| S10954 | 2025.04.02 | N24W18 | |||||||||
| 14052 | 2025.04.03 2025.04.04 |
2 | 1 | S21W62 | 0005 | BXO |
 |
 |
was AR S10955 location: S21W61 |
||
| 14051 | 2025.04.03 2025.04.04 |
S08W84 |
 |
was AR S10956 location: S07W82 |
|||||||
| S10957 | 2025.04.03 | N31W41 | |||||||||
| 14053 | 2025.04.04 2025.04.04 |
1 | S09W47 | 0001 | AXX |
 |
 |
was AR S10958 location: S08W32 |
|||
| 14055 | 2025.04.04 2025.04.05 |
2 | 16 | 4 | N09E21 | 0010 | AXX | DRI |
 |
 |
was AR S10959 area: 0030 location: N08E22 |
| 14054 | 2025.04.04 2025.04.05 |
9 | 36 | 16 | S12W03 | 0110 | DAO | DKI |
 |
 |
was AR S10960 area: 0410 location: S12W02 |
| S10961 | 2025.04.04 | N06E34 | |||||||||
| S10962 | 2025.04.04 | N25W19 | |||||||||
| S10963 | 2025.04.05 | N14W31 |
 |
||||||||
| S10964 | 2025.04.05 | 1 | 1 | N08E69 | 0010 | HRX |
 |
 |
|||
| 14056 | 2025.04.05 2025.04.06 |
1 | 1 | 1 | S05E69 | 0050 | HSX | HSX |
 |
 |
was AR S10966 location: S06E72 area: 0140 |
| S10967 | 2025.04.06 | 2 | N11W13 | 0003 | AXX |
 |
|||||
| S10968 | 2025.04.06 | 1 | N20E36 | 0001 | AXX |
 |
|||||
| S10969 | 2025.04.06 | 1 | 1 | N13E73 | 0004 | AXX |
 |
||||
| Total spot count: | 50 | 168 | 69 | ||||||||
| Sunspot number: | 140 | 308 | 179 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 90 | 212 | 113 | (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): | 154 | 169 | 143 | ||||||||
| 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 | 181.0 (1) | 25.1 (2A) / 150.4 (2B) / 173.1 (2C) | (128.8 projected, -4.6) | (23.0) | |
| 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). Currently all 365 days smoothed indices are still indicating that a peak occurred on October 12 or 13, 2024. Should sunspot activity decrease even further then there is a possibility that the peak may have taken place in September 2024. Any peak outside of September-October 2024 appears unlikely. The 365 days average solar flux is likely to max out ~2% below the peak of solar cycle 23. The maximum 365d smoothed solar flux of SC23 and SC25 are similar, however, sunspot numbers were significantly lower during SC25 compared to SC23.
--------------------------------------------------------------------------------------
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.
