Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 30, 2025 at 06:35 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 levels on April 29. An isolated active interval was observed early on April 30. Solar wind speed at SOHO ranged between 377 and 463 km/sec, averaging 426 km/sec (+22 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet levels. The above 10 MeV proton flux was at background levels.

Solar flux density measured at 20h UT on 2.8 GHz was 149.2 - decreasing 30.7 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 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.3). Three hour interval K indices: 01221122 (planetary), 02322322 (Boulder), 01222221 (Andenes).

The background x-ray flux is at the class B8 level (GOES 19).

At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 212) and in 9 active regions using 1K resolution (SN: 128) SDO/HMI images.

AR 14068 [S25W36] decayed slowly and quietly.
AR 14070 [S12W59] decayed slowly and was mostly quiet. C1 flares: C1.3 @ 14:01, C1.2 @ 18:58, C1.5 @ 22:13 UT
AR 14072 [S19W16] decayed slowly and quietly.
AR 14075 [S09W07] decayed slowly and was mostly quiet. C1 flares: C1.9 @ 09:31 UT
AR 14076 [N05E04] was quiet and stable.
AR 14077 [S17E07] decayed significantly and was mostly quiet. C1 flares: C1.1 @ 19:27 UT
AR 14078 [N15W60] developed early in the day, then produced 2 M flares just before noon. The region then decayed substantially and lost most spots and area after noon.
AR 14079 [N08E68] is a large and compact spot group with a huge leading penumbra. A major flare is possible. C1 flares: C1.4 @ 01:51, C1.6 @ 02:29, C1.4 @ 02:41, C1.4 @ 03:10, C1.7 @ 04:19, C1.6 @ 04:47, C1.3 @ 07:41, C1.3 @ 12:44, C1.3 @ 12:51, C1.8 @ 13:03, C1.2 @ 17:31, C1.5 @ 17:54, C1.3 @ 19:32, C1.1 @ 23:06 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S11021 [N19E26] was quiet and stable.
S11027 [S15E14] reemerged with tiny spots.
New region S11029 [S22E35] emerged with tiny spots.
New region S11030 [N13E47] emerged with tiny spots.

A C1.6 flare was recorded at 00:42 UT from a location behind the northwest limb.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.4 04:56   14079 GOES19  
C4.0 05:03   14079 GOES19  
M1.7 05:13 N10E77 14079 GOES19  
C4.9 05:27   14079 GOES19  
C2.2 06:56   14079 GOES19  
C6.5 09:54   14070 GOES19  
M1.3/1N 10:02 N15W50 14078 GOES19  
M1.6/1N 10:57 N15W51 14078 GOES19  
C2.7 12:12   14079 GOES19  
C5.3 15:05 N10E70 14079 GOES19  
C2.0 16:47   14070 GOES19  
C7.3 23:25 S32W90 14065 GOES19  

Coronal mass ejections (CMEs)

April 27-29: No obviously Earth directed CMEs.

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 recurrent trans equatorial negative polarity coronal hole (CH1289) rotated across the central meridian on April 28-29. A small recurrent trans equatorial negative polarity coronal hole (CH1290) will likely rotate into an Easrth facing position on May 1.

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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be at quiet to active levels on April 30. Quiet to unsettled levels are possible on May 1-2 due to effects associated with CH1288.

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
14065 2025.04.16
2025.04.17
1     S31W91 0020 HSX     was AR S10990

location: S32W89

rotated out of view

14078 2025.04.19
2025.04.28
4 5 1 N16W61 0020 CRO CRO was AR S10999

location: N15W60

area: 0015

14068 2025.04.20
2025.04.21
1 5   S24W44 0010 AXX AXX was AR S11002

location: S25W36

area: 0005

14070 2025.04.20
2025.04.22
7 12 7 S12W58 0070 DSO DAO

was AR S11004

area: 0130

location: S12W59

14069 2025.04.20
2025.04.22
      S07W87           was AR S11006

location: S08W88

S11009 2025.04.21       S08W37            
14072 2025.04.22
2025.04.23
5 18 11 S18W18 0060 DAI DRI beta-gamma

was AR S11011

area: 0080

location: S19W16

14073 2025.04.23
2025.04.24
      N11W28        

was AR S11015

location: N12W27

14076 2025.04.23
2025.04.25
1 6 1 N06E04 0080 HSX CSO was AR S11017

area: 0190

location: N05E04

14075 2025.04.23
2025.04.25
  2   S11W08 0005   AXX was AR S11018

location: S09W07

14077 2025.04.24
2025.04.25
1 7 2 S17E04 0010 AXX CRO was AR S11020

location: S17E97

S11021 2025.04.24       N19E13          
S11022 2025.04.24       N23W25          
S11025 2025.04.25   2 1 S11W19 0004   AXX  
S11026 2025.04.26       S23W28            
S11027 2025.04.26   3   S15E19 0006   BXO    
14079 2025.04.28
2025.04.28
5 27 12 N08E67 0560 EHI EKC was AR S11028

area: 1420

location: N08E68

S11029 2025.04.29   3 1 S22E35 0006   BXO    
S11030 2025.04.29   2 2 N13E47 0007   BXO    
Total spot count: 25 92 38  
Sunspot number: 105 212 128  (total spot count + 10 * number of spotted regions)
Weighted SN: 58 121 67  (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): 116 117 102  

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)
2024.06 184.3 190.2 164.1 152.8 (+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
2025.04 163.0 (1)   121.3 (2A) / 125.5 (2B) / 144.1 (2C)
ISN average: 138
(128.9 projected, -4.6) (18.2)
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

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 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.