Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 10, 2025 at 07:35 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 (May 1, 2025)
Solar cycle Solar cycles 23-25 (May 1, 2025) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (May 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 (May 1, 2025) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (May 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 May 9 under the influence of effects from CH1291. Solar wind speed at SOHO ranged between 420 and 504 km/sec, averaging 466 km/sec (-9 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 136.2 - decreasing 29.2 over the previous solar rotation. The 365 days average solar flux at 1 AU was 193.76 (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 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.5). Three hour interval K indices: 32122344 (planetary), 23222424 (Boulder), 53224565 (Andenes).

The background x-ray flux is at the class B6 level (GOES 19).

At the time of counting spots (see image time), spots were observed in 9 active regions using 2K resolution (SN: 174) and in 6 active regions using 1K resolution (SN: 94) SDO/HMI images.

AR 14079 [N07W67] decayed further and continued to produce mostly low level C flares. C1 flares: C1.9 @ 03:04, C1.8 @ 04:30, C1.0 @ 06:40, C1.4 @ 07:16, C1.6 @ 08:27, C1.0 @ 09:23, C1.1 @ 10:11, C1.2 @ 12:24, C1.1 @ 14:47, C1.0 @ 15:11, C1.0 @ 20:21 UT
AR 14081 [N07W38] decayed significantly and was mostly quiet.
AR 14082 [S09W09] decayed further and was mostly quiet. C1 flares: C1.0 @ 06:19 UT
AR 14084 [S20E48] decayed losing all trailing spots.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S11049 [S16W23] saw new flux emerged and a few spots developed.
S11051 [N11E07] was quiet and stable.
New region S11052 [N04W37] emerged just south of AR 14081 with a few spots.
New region S11053 [N07E06] emerged with tiny spots.
New region S11054 [N10E34] was observed with tiny spots in an old plage area.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.2 03:20   14079 GOES19  
C4.9 11:21   14079 GOES19  

Coronal mass ejections (CMEs)

May 7-9: 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 southern hemisphere negative polarity coronal hole (CH1291) rotated across the central meridian on May 4-8. A northern hemisphere positive polarity coronal hole (CH1292) was Earth facing on May 7-8.

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 fair.

Forecast

The geomagnetic field is expected to be at quiet to active levels on May 10-12 due to effects from CH1291.

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
14079 2025.04.28
2025.04.28
16 25 13 N08W67 1100 DKC DKC beta-gamma

was AR S11028

area: 1060

location: N07W67

14081 2025.05.01
2025.05.03
13 18 8 N07W37 0130 DAI DAO

was AR S11034

location: N07W38

14082 2025.05.03
2025.05.04
5 14 6 S10W07 0050 CSO DSO

was AR S11040

area: 0170

location: S09W09

S11041 2025.05.03       S17W23            
S11042 2025.05.03       S03W41            
14083 2025.05.04
2025.05.05
      N18W81           was AR S11043

location: N18W74

S11047 2025.05.06       S22W41            
S11048 2025.05.06       N24W19            
S11049 2025.05.06   5 2 S16W23 0010   BXO  
14084 2025.05.07
2025.05.08
3 3 2 S21E48 0060 CSO HAX was AR S11050

location: S20E48

area: 0100

S11051 2025.05.08   5   N11E07 0007   BXO  
S11052 2025.05.09   8 3 N04W37 0015   CRO    
S11053 2025.05.09   3   N07E06 0006   BXO    
S11054 2025.05.09   3   N10E34 0006   BXO    
Total spot count: 37 84 34  
Sunspot number: 77 174 94  (total spot count + 10 * number of spotted regions)
Weighted SN: 62 112 62  (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): 85 96 75  

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
2023.11 153.5 150.2 107.1 127.9 (+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
2024.10 221.0 219.6 165.8 160.8 (+1.4) 18.99
2024.11 199.6 195.3 154.1 (159.0 projected, -1.8) 9.33
2024.12 197.3 191.2 154.6 (155.2 projected, -3.8) 8.42
2025.01 190.3 184.2 137.0 (149.7 projected, -5.5) 13.17
2025.02  184.2 179.7 154.7 (141.6 projected, -7.1) 14.42
2025.03 163.7 162.1 134.2 (135.1 projected, -6.5) 15.96
2025.04 162.5 163.6 140.6 (130.5 projected, -4.6) 17.9
2025.05  152.1 (1)   22.9 (2A) / 78.8 (2B) / 125.0 (2C) (125.2 projected, -5.3) (21.4)
2025.06       (120.3 projected, -4.9)  
2025.07       (116.1 projected, -4.2)  
2025.08       (111.4 projected, -4.7)  
2025.09       (107.1 projected, -4.3)  
2025.10       (103.2 projected, -3.9)  

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. STAR 1K 365d peak: 236.1, STAR 2K 365d peak: 364.3, NOAA SN 365d peak: 156.0, ISN 365d peak: 163.6. The 365d smoothed solar flux peaked on October 13, 2024, just 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.