Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 23, 2025 at 06:00 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 active levels on April 22 due to effects from CH1286. Solar wind speed at SOHO ranged between 597 and 711 km/sec, averaging 651 km/sec (+44 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to major storm levels. The above 10 MeV proton flux was at background levels.

Solar flux density measured at 20h UT on 2.8 GHz was 163.4 - increasing 12.0 over the previous solar rotation. The 365 days average solar flux at 1 AU was 194.54 (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 37 (STAR Ap - based on the mean of three hour interval ap indices: 37.4). Three hour interval K indices: 43322333 (planetary), 33423322 (Boulder), 44323365 (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 18 active regions using 2K resolution (SN: 362) and in 13 active regions using 1K resolution (SN: 223) SDO/HMI images.

AR 14062 [S03W30] decayed slowly and was mostly quiet. C1 flares: C1.7 @ 07:23 UT
AR 14063 [N05W77] decayed slowly and was mostly quiet. C1 flares: C1.6 @ 03:18 UT
AR 14064 [N10E08] gained spots in the trailing spot section and a tiny magnetic delta configuration formed. Otherwise the region was in slow decay. C1 flares: C1.7 @ 21:21 UT
AR 14065 [S31W00] decayed slowly and produced a C2.9 flare at 08:21 UT. This flare was associated with a CME that may have an Earth directed component.
AR 14067 [S02W03] decayed further and was quiet.
AR 14068 [S26E49] was mostly quiet and stable. C1 flares: C1.8 @ 18:30 UT
New AR 14069 [S08E09] emerged on April 20 and was numbered by SWPC 2 days later. A minor M class flare is possible. C1 flares: C1.6 @ 06:40 UT
New AR 14070 [S12E39] emerged on April 20 and got its NOAA number 2 days later as development continued.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10997 [S12W63] was quiet and stable.
S10998 [S14W67] was quiet and stable. Note that SWPC numbered AR 14071 on April 22 including both ARs S10997 and S10989 in that region.
S10999 [N16E35] was mostly quiet and stable.
S11003 [S18W29] was quiet and stable.
S11009 [S05E62] decayed after the C9 flare early in the day.
New region S11010 [N23E13] was observed with tiny spots in an old plage area.
New region S11011 [S17E78] rotated into view with a mature spot.
New region S11012 [S14E22] was observed with tiny spots in an old plage area.
New region S11013 [N22W26] emerged with a tiny spot.
New region S11014 [S22W11] emerged with a tiny spot.

A C1.5 flare was recorded at 22:33 UT from a location at the southeast limb.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C9.9 01:00   S11009 GOES19  
C2.9 08:21 S30E09 14065 GOES19 CME
C2.8 09:08   14069 GOES19 CME
C3.3 09:41 S13W58 (SDO/AIA) S10998 GOES19  
M1.3 10:48 behind NW limb 14060 GOES19 LDE, CME
C3.3 12:13   S10999 GOES19  
C2.6 18:57   14062 GOES19  
C2.2 19:52   14068 GOES19  
C2.1 20:01   14068 GOES19  

Coronal mass ejections (CMEs)

April 20-21: 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) will rotate across the central meridian on April 17-24. A small northern hemisphere positive polarity coronal hole (CH1287) will likely become Earth facing on April 22. Another northern hemisphere positive polarity coronal hole (CH1288) will likely become 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 to fair.

Forecast

The geomagnetic field is expected to be at quiet to unsettled levels on April 23-27 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
15 36 19 S02W32 0130 DAI CAO beta-gamma

was AR S10984

area: 0270

location: S03W30

S10985 2025.04.14       N05W31            
14063 2025.04.15
2025.04.16
2 4 2 N05W79 0010 CRO CRO

was AR S10987

area: 0020

location: N05W77

14064 2025.04.15
2025.04.16
18 37 24 N11W07 0250 EHI EAC

beta-gamma-delta

was AR S10989

location: N10W03

area: 0370

14065 2025.04.16
2025.04.17
1 5 2 S31W02 0070 HSX CSO

was AR S10990

location: S31W00

S10992 2025.04.16       N15W41          
14066 2025.04.17       S05W19           these are 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
2 6 1 S03E01 0010 BXO CRO was AR S10994

location: S02W03

S10995 2025.04.17       N03W35            
S10996 2025.04.18       N32W50            
S10997 2025.04.18   8 4 S12W63 0025   BXO  
S10998 2025.04.19   6 3 S14W67 0020   CRI  
S10999 2025.04.19   6   N16E35 0008   BXO  
S11000 2025.04.19       S10W18            
14068 2025.04.20
2025.04.21
3 10 5 S26E46 0070 DSO DSO was AR S11002

location: S26E49

area: 0120

S11003 2025.04.20   6 5 S18W29 0015   BXO  
14070 2025.04.20
2025.04.22
4 22 14 S12E38 0040 CAO DRI was AR S11004

area: 0120

location: S12E39

S11005 2025.04.20       N23E13            
14069 2025.04.20
2025.04.22
4 20 12 S08E07 0020 CAO DAI was AR S11006

area: 0200

location: S08E09

S11007 2025.04.21       N10E13          
S11008 2025.04.21       S18W57          
S11009 2025.04.21   2 1 S05E62 0006   AXX  
14071 2025.04.22 3     S13W69 0010 BXO       probably SWPC regards ARs S10997 and S10998 as one region
S11010 2025.04.22   6   N23E13 0010   AXX    
S11011 2025.04.22   2 2 S17E78 0130   HSX    
S11012 2025.04.22   4   S14E22 0008   BXO    
S11013 2025.04.22   1   N22W26 0001   AXX    
S11014 2025.04.22   1   S33W11 0001   AXX    
Total spot count: 52 182 94  
Sunspot number: 142 362 224  (total spot count + 10 * number of spotted regions)
Weighted SN: 90 224 136  (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): 156 199 179  

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
2025.04 164.2 (1)   88.7 (2A) / 121.0 (2B) / 140.2 (2C)
ISN average: 130
(128.8 projected, -4.6) (22.0)
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

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.