Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 25, 2024 at 09:50 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, 2024)
Solar cycle Solar cycles 23-25 (May 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (May 1, 2024) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (July 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (May 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (May 1, 2024) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (March 3, 2024) 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 May 24. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was at background levels at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 162.8 - increasing 10.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 161.13. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 161.13 on November 24, 2023). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5). Three hour interval K indices: 23332101 (planetary), 33233212 (Boulder), 34333322 (Andenes).

The background x-ray flux is at the class C1 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 11 active regions using 2K resolution (SN: 219) and in 11 active regions using 1K resolution (SN: 160) SDO/HMI images.

Region 13684 [S06W66] decayed slowly and quietly.
Region 13685 [S14W35] decayed slowly and was mostly quiet.
Region 13686 [S08W27] decayed slowly and quietly.
Region 13689 [S09E18] was mostly quiet and stable.
Region 13690 [N17E63] was quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9715 [N19W66] was quiet and stable.
S9729 [S09W82] decayed slowly and rotated partly out of view producing many C and M flares.
S9730 [S17W31] decayed substantially and was quiet.
New region S9735 [N24E77] rotated into view as a compact spot group with a few large spots. An M class flare is possible.
New region S9736 [N09W37] emerged with a tiny spot.
New region S9737 [S09E36] emerged with a tiny spot.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C3.0 00:19   S9733 GOES16  
C2.8 00:31   S9733 GOES16  
C3.3 00:38   S9733 GOES16  
C4.6 01:14   S9729 GOES16  
C2.3 02:18   S9733 GOES16  
C4.8 02:49   S9729 GOES16  
C4.1 03:11   S9729 GOES16  
C2.5 03:35   S9733 GOES16  
C2.5 04:11   S9729 GOES16  
C2.5 04:23   S9729 GOES16  
C2.4 04:37   S9729 GOES16  
C3.0 04:49   S9729 GOES16  
C3.2 05:24 S07W78 S9729 GOES16  
C3.6 05:41   S9729 GOES16  
C3.9 06:07   13685 GOES16  
C3.3 06:27   S9729 GOES16  
M1.4 07:05   13685 GOES16 incorrectly attributed to AR 13679 by SWPC
M1.0 08:01 S09W81 S9729 GOES16  
M1.3 08:24   13685 GOES16 simultaneous flare in AR S9735
C7.7 08:46   S9729 GOES16  
C9.4 09:00   S9729 GOES16  
C9.7 09:11   S9729 GOES16  
C4.0 09:35   S9729 GOES16  
C5.6 10:51 S10W76 S9729 GOES16  
C3.5 11:08   S9729 GOES16  
C2.6 11:42   S9729 GOES16  
C2.4 13:33   S9729 GOES16  
C3.4 13:58 S11W26 13685 GOES16  
C2.6 14:22   S9729 GOES16  
C2.4 18:20   S9729 GOES16  
M1.4 20:25   S9729 GOES16  
C3.6 22:04 northwest limb S9733 GOES16  

Coronal mass ejections (CMEs)

May 22-24: No obviously Earth directed CME observed.

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 negative polarity northern hemisphere coronal hole (CH1222) - an extension of the northern polar coronal hole - was in an Earth facing position on May 21-22. A small negative polarity southern hemisphere coronal hole (CH1223) will likely rotate across the central meridian on May 26.

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 May 25-26 due to weak effects from CH1222. Quiet conditions are likely on May 27-28.

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
Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
13679 2024.05.12 8     S08W86 0360 EKC     rotated out of view
13682 2024.05.12
2024.05.14
      N19W69          

SWPC location on May 22 was N13W50, the next day the spotless region was inexplicably at N18W67, and yet another day later the region was repositioned to N19W69

location: N14W73

13684 2024.05.15
2024.05.16
6 8 4 S07W65 0080 CSO CAO beta-gamma

location: S06W66

area: 0120

13685 2024.05.15
2024.05.16
14 25 9 S13W36 0320 EHC DHO

location: S14W35

area: 0370

S9715 2024.05.15   3 1 N19W66 0010   BXO  
13686 2024.05.16
2024.05.17
6 20 9 S08W28 0080 CAO CAO

area: 0150

location: S08W27

S9720 2024.05.16       S30W50            
S9721 2024.05.17       S19W39            
13687 2024.05.19       N17W70           part of AR 13682

SWPC moved this AR to the location of AR S9715 on May 23

13688 2024.05.19       S12W14            
S9724 2024.05.19       S14W20            
13689 2024.05.19 5 18 8 S08E17 0010 CRO DRI

location: S09E18

area: 0050

S9726 2024.05.19       S19W42            
S9729 2024.05.21   3 1 S09W82 0240   CAO  
S9730 2024.05.21   19 9 S17W31 0040   CRI  
S9731 2024.05.21       S24E11            
13690 2024.05.23
2024.05.23
1 1 1 N17E60 0040 HSX HSX

location: N17E63

area: 0090

S9733 2024.05.23       N27W88          
S9735 2024.05.24   10 6 N24E77 0400   DKC    
S9736 2024.05.24   1 1 N09W37 0004   AXX    
S9737 2024.05.24   1 1 S09E36 0002   AXX    
Total spot count: 40 109 50  
Sunspot number: 100 219 160  (total spot count + 10 * number of spotted regions)
Weighted SN: 78 155 96  (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): 110 120 128  

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
2022.10 133.5 132.7 95.5 98.9 (+2.4) 11.16
2022.11 123.4 120.7 80.5 101.2 (+2.3) 9.33
2022.12 147.9 143.4 112.8 106.7 (+5.5) 10.99
2023.01 182.4 176.6 144.4 113.3 (+6.6) 8.73
2023.02 167.2 163.2 111.3 117.8 (+3.5) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 123.3 121.1 (+3.3) 14.42
2023.04 145.4 146.4 97.6 122.9 (+1.8) 13.40
2023.05 155.6 159.2 137.4 124.2 (+1.3) 10.67
2023.06 161.7 166.8 160.5 125.3 (+1.1) 8.95
2023.07  176.4 182.2 160.0 124.4 (-0.9) 8.15
2023.08  153.7 157.6 114.8 124.1 (-0.3) 7.19
2023.09  154.4 156.0 134.2 123.9 (-0.2) 14.26
2023.10  142.8 141.9 99.4 124.8 (+0.9) 8.16
2023.11 153.5 150.2 105.4 (125.2 projected, +0.4) 12.20
2023.12 151.1 146.4 114.2 (121.9 projected, -3.3) 9.60
2024.01 164.6 159.3 123.0 (118.5 projected, -3.4) 5.46
2024.02 172.5 168.3 124.7 (117.7 projected, -0.8) 5.31
2024.03 154.4 152.9 104.9 (117.1 projected, -0.6) 11.03
2024.04 161.3 162.6 136.5 (117.1 projected, -0.0) 9.69
2024.05 193.9 (1)   115.9 (2A) / 149.8 (2B) / 183.3 (2C) (118.3 projected, +1.2) (28.5)
2024.06       (117.4 projected, -0.9)  
2024.07       (115.7 projected, -1.7)  
2024.08       (113.8 projected, -1.9)  
2024.09       (112.5 projected, -1.3)  
2024.10       (111.1 projected, -1.4)  
2024.11       (108.6 projected, -2.5)  

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 30 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 28, 2024

The big increase in sunspot counts during the April 14-27 interval caused a major uptick in the smoothed SNs and solar flux. It's not yet clear when the next peak will be, anytime between October 28 and December 20, 2023 looks possible. The 365d smoothed solar flux exceeded the June 27 peak on October 28, while the 365d smoothed ISN and NOAA SN both exceeded the June 2023 peak in late October 2023. It should be noted that the current peak using 13-month smoothing is still in June 2023.

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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.