Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 24, 2025 at 03:55 UT.

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data since 2003.01 (April 4, 2025)
Solar cycle Solar cycles 23-25 (April 1, 2025) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (April 1, 2025) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (August 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (April 1, 2025) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (April 1, 2025) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (April 21, 2025) Cycle 25 spots (final update December 25, 2019)
  Solar cycles 24-25 transition using 365d smoothing Research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing
Calculating the Strength of Solar Cycle 25 Using 365-day Smoothing

Recent activity

The geomagnetic field was at quiet to unsettled levels on April 23. Solar wind speed at SOHO ranged between 490 and 628 km/sec, averaging 525 km/sec (-126 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to unsetted levels. The above 10 MeV proton flux was at background levels.

Solar flux density measured at 20h UT on 2.8 GHz was 167.7 - increasing 15.1 over the previous solar rotation. The 365 days average solar flux at 1 AU was 194.39 (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: 12232111 (planetary), 13232221 (Boulder), 23222212 (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 20 active regions using 2K resolution (SN: 362) and in 16 active regions using 1K resolution (SN: 237) SDO/HMI images.

AR 14062 [S03W44] decayed slowly and was mostly quiet.
AR 14064 [N10W17] lost area but gained some spots. Several low level C flares were recorded. C1 flares: C1.3 @ 13:07, C1.7 @ 20:29 UT
AR 14065 [S32W13] decayed slowly and quietly.
AR 14067 [S03W16] gained a few spots and was quiet.
AR 14068 [S27E37] was mostly quiet and stable.
AR 14069 [S08W06] decayed significantly and was mostly quiet. C1 flares: C1.5 @ 16:52 UT
AR 14070 [S12E26] developed before noon producing several low level C flares, then began to mature. C1 flares: C1.3 @ 05:42, C1.4 @ 09:21, C1.5 @ 10:43, C1.3 @ 11:25, C1.8 @ 13:49, C1.7 @ 14:13, C1.8 @ 14:24, C1.7 @ 19:37, C1.7 @ 21:59, C1.7 @ 23:07 UT
New AR 14072 [S18E64] rotated into view on April 22 and was numbered the next day by SWPC.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10997 [S12W76] decayed slowly and quietly.  Note that SWPC numbered AR 14071 on April 22 including both ARs S10997 and S10998 in that region.
S10999 [N16E25] was mostly quiet and stable. C1 flares: C1.9 @ 07:06 UT
S11000 [S20W34] reemerged with tiny spots.
S11003 [S18W41] decayed slowly and quietly.
S11009 [S07E49] decayed slowly and quietly.
S11010 [N22W00] was quiet and stable.
S11012 [S17E09] was quiet and stable.
New region S11015 [N11E53] emerged with a few spots.
New region S11016 [S09W29] emerged with tiny spots.
New region S11017 [N06E84] rotated into view with a mature spot.
New region S11018 [S10E73] rotated into view with a tiny spot.
New region S11019 [N34W42] emerged with a tiny spot.

A C1.7 flare was recorded at 18:06 and a C1.8 flare at 18:24 UT from a location at the southeast limb.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.0 02:34   S10999 GOES19  
C2.8 14:44 N10W13 14064 GOES19  
C3.9 14:55 N11W13 14064 GOES19  
C2.2 15:35   14070 GOES19  
C2.7 16:06   14064 GOES19  
C2.3 23:28   14070 GOES19  

Coronal mass ejections (CMEs)

April 21, 23: No obviously Earth directed CMEs.
April 22: A number of CMEs were observed during the day. The only one that might have an Earth directed company was observed after a C2.9 flare in AR 14065 when that region was rotating across the central meridian. While most of the CME was directed due south, there is a chance of CME effects on April 25.

Coronal holes

[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 17-24. A small northern hemisphere positive polarity coronal hole (CH1287) was Earth facing on April 22. Another northern hemisphere positive polarity coronal hole (CH1288) will be Earth facing on April 24.

Propagation

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.

Forecast

The geomagnetic field is expected to be at quiet to unsettled levels on April 24-27 due to effects from CH1286. Effects from CH1287 could add to the disturbance on April 25-26, while CH1288 could contribute some unsettled and active intervals on April 27-28. The April 22 CME could reach Earth on April 25 and cause some active and minor storm intervals.

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.

Active solar regions



(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
14062 2025.04.14
2025.04.15
12 11 5 S03W45 0140 DAI CAO beta-gamma

was AR S10984

area: 0200

location: S03W44

S10985 2025.04.14       N05W44            
14064 2025.04.15
2025.04.16
16 44 25 N11W18 0210 EAI EAI

beta-gamma

was AR S10989

location: N10W17

area: 0350

14065 2025.04.16
2025.04.17
3 2 1 S31W14 0070 CSO CSO

was AR S10990

location: S32W13

S10992 2025.04.16       N15W54            
14066 2025.04.17       S05W33           these were the trailing spots of AR 14062. There was no obvious reason for SWPC's split, which would make this an interpretational mistake
14067 2025.04.17
2025.04.18
  12 3 S03W19 0030   CRO beta-gamma

was AR S10994

location: S03W16

S10995 2025.04.17       N03W48            
S10997 2025.04.18   3 2 S12W76 0020   DRO  
S10998 2025.04.19       S14W80          
S10999 2025.04.19   16 3 N16E25 0025   BXO  
S11000 2025.04.19   3 1 S20W34     AXX    
14068 2025.04.20
2025.04.21
3 9 6 S26E35 0060 DSO DAO was AR S11002

location: S27E37

area: 0110

S11003 2025.04.20   1   S20W34 0002   AXX  
14070 2025.04.20
2025.04.22
9 18 12 S12E24 0070 DAI DAI was AR S11004

area: 0320

location: S12E26

14069 2025.04.20
2025.04.22
5 17 10 S08W05 0060 DAO DAO was AR S11006

location: S08W06

S11007 2025.04.21       N10W00            
S11009 2025.04.21   1 1 S07E49 0002   AXX  
14071 2025.04.22 3     S13W89 0010 BXO       SWPC probably regarded ARs S10997 and S10998 as one region
S11010 2025.04.22   4   N22W00 0005   AXX  
14072 2025.04.22
2025.04.23
1 3 2 S18E62 0080 HSX CSO was AR S11011

area: 0130

location: S18E64

S11012 2025.04.22   5   S17E09 0010   BXO  
S11013 2025.04.22       N22W39          
S11014 2025.04.22       S33W24          
S11015 2025.04.23   4 2 N11E53 0030   CRO    
S11016 2025.04.23   6 2 S09W29 0012   CRO    
S11017 2025.04.23   1 1 N06E84 0190   HSX    
S11018 2025.04.23   1 1 S10E73 0002   AXX    
S11019 2025.04.23   1   N34W42 0002   AXX    
Total spot count: 52 162 77  
Sunspot number: 132 362 237  (total spot count + 10 * number of spotted regions)
Weighted SN: 87 214 129  (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): 145 199 190  

Monthly solar cycle data

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
2024.10 221.0 219.6 165.8 (160.2 projected, +0.9) 18.99
2024.11 199.6 195.3 154.1 (157.6 projected, -2.6) 9.33
2024.12 197.3 191.2 154.6 (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
2025.04 164.4 (1)   93.1 (2A) / 121.4 (2B) / 145.9 (2C)
ISN average: 132
(128.8 projected, -4.6) (21.3)
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

Solar cycles 24-25

Smoothed SF and sunspot numbers

Update on the progress of solar cycle 25 as of April 14, 2025

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.

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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.